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Author Topic: Tascam DR-70D - modification discussion  (Read 20174 times)

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Offline voltronic

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Tascam DR-70D - modification discussion
« on: July 23, 2015, 07:59:43 PM »
So as to not crowd the main 70D thread with mod discussions, I'm starting this topic.  It would be interesting to hear recordings of modified units for those who have had them done.  This may help people decide whether or not such mods are worth their while.  So far, the only known mods are from Jim Williams (described on the FAQ) and Busman Audio.

My JWmod 70D arrived today, and now I have before and after recordings to share of me playing a short piano excerpt.  As I said in the main thread, this is not really a valid comparison as the ambient noise in my apartment is somewhat high (DVR box and computer in same room, appliances, etc.) and the recordings are made more than a week apart.  I did my best to keep my playing in the second recording somewhat consistent with the first recording, and other than the tempo I think I got pretty close.

For those that care, this is a Yamaha U1 upright, up against an interior wall and definitely overdue for a tuning.  I'm playing very softly, although it doesn't seem so on the recording because I was using the HIGH gain setting.

Jim established that there wouldn't really be much reduction in self-noise, but there should be an improvement in detail / transparency in the mid and high ranges.  These recordings are probably not the best to judge those things, but I had to go with something I could reasonably repeat most of the factors with.

The recording setup was exactly the same both times: CM3s in NOS, 5 feet up, 6ft away and at 3:30 position behind and to the right of keyboard.  I did this to sound like you're sitting in a chair reading the music over the pianist's shoulder.  This was direct into the 70D, running at 24/96, HIGH gain, pots at 10:30.  The ambient noise before I started playing was reading about -45 to -50 dB for both recordings.

No editing was performed on these files, other than trimming the start and end and converting to FLAC.

The files are labelled A and B, but I'm curious to see if others can tell which one is the stock unit and which one is modified.  I'll withhold my thoughts on how this turned out until we have some guesses as to which file is which.

EDIT: No more mystery - they are just labeled as what they are.  I also uploaded a noise-reduced version of both files to remove the background hum from my DVR box and fridge.
https://www.dropbox.com/sh/adfu4jc5z1r1qx9/AABMBw5LWl7rrekjqKhgQOCXa?dl=0
« Last Edit: February 06, 2016, 04:30:06 PM by voltronic »
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Offline Colin Liston

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Re: Tascam DR-70D - modification discussion
« Reply #1 on: July 25, 2015, 08:09:34 AM »
How much is the mod?
Occasionally....music mics record

Offline voltronic

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Re: Tascam DR-70D - modification discussion
« Reply #2 on: July 25, 2015, 08:57:03 AM »
How much is the mod?

Jim Williams does not do the mod himself - he modified his own 70D, and then made the details of it free for anyone who wants to do it themselves.  I have posted this on the FAQ page.

You need to find a surface-mount shop to do this for you, so the price will vary.  My shop asked that I source the parts myself as well.  Parts came to $27.06 shipped, and that included one extra opamp and two extra caps just in case.  USPS was $17.90, labor and return shipping $91.00.  All together it ran me $135.96.

Other shops may charge a bit more for labor.  The shop I used said they could charge me a bit less based on what they had learned from doing one of these before.  They don't want to be publicly named, as they don't really have time to do lots of these, sorry.

I think at least one person here has gotten the Busman mod.  I don't know anything about that, as he doesn't advertise it on his website.
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Offline Life In Rewind

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Re: Tascam DR-70D - modification discussion
« Reply #3 on: July 25, 2015, 09:40:12 AM »
How much is the mod?

Jim Williams does not do the mod himself - he modified his own 70D, and then made the details of it free for anyone who wants to do it themselves.  I have posted this on the FAQ page.

You need to find a surface-mount shop to do this for you, so the price will vary.  My shop asked that I source the parts myself as well.  Parts came to $27.06 shipped, and that included one extra opamp and two extra caps just in case.  USPS was $17.90, labor and return shipping $91.00.  All together it ran me $135.96.

Other shops may charge a bit more for labor.  The shop I used said they could charge me a bit less based on what they had learned from doing one of these before.  They don't want to be publicly named, as they don't really have time to do lots of these, sorry.

I think at least one person here has gotten the Busman mod.  I don't know anything about that, as he doesn't advertise it on his website.

Only True Believers need apply! ;D
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Offline voltronic

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Re: Tascam DR-70D - modification discussion
« Reply #4 on: July 25, 2015, 10:06:11 AM »
How much is the mod?

Jim Williams does not do the mod himself - he modified his own 70D, and then made the details of it free for anyone who wants to do it themselves.  I have posted this on the FAQ page.

You need to find a surface-mount shop to do this for you, so the price will vary.  My shop asked that I source the parts myself as well.  Parts came to $27.06 shipped, and that included one extra opamp and two extra caps just in case.  USPS was $17.90, labor and return shipping $91.00.  All together it ran me $135.96.

Other shops may charge a bit more for labor.  The shop I used said they could charge me a bit less based on what they had learned from doing one of these before.  They don't want to be publicly named, as they don't really have time to do lots of these, sorry.

I think at least one person here has gotten the Busman mod.  I don't know anything about that, as he doesn't advertise it on his website.

Only True Believers need apply! ;D

I'm not sure where your snark is directed - at the mod I got, at Busman, or at all of this in general.
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Offline groovon

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Re: Tascam DR-70D - modification discussion
« Reply #5 on: July 25, 2015, 11:19:38 AM »
How much is the mod?

Jim Williams does not do the mod himself - he modified his own 70D, and then made the details of it free for anyone who wants to do it themselves.  I have posted this on the FAQ page.

You need to find a surface-mount shop to do this for you, so the price will vary.  My shop asked that I source the parts myself as well.  Parts came to $27.06 shipped, and that included one extra opamp and two extra caps just in case.  USPS was $17.90, labor and return shipping $91.00.  All together it ran me $135.96.

Other shops may charge a bit more for labor.  The shop I used said they could charge me a bit less based on what they had learned from doing one of these before.  They don't want to be publicly named, as they don't really have time to do lots of these, sorry.

I think at least one person here has gotten the Busman mod.  I don't know anything about that, as he doesn't advertise it on his website.

Has anyone seen a schematic of the input circuit? I'm very curious, as just two dual (NE5532) opamps to cover four balanced inputs seems a bit low on the 'parts count' (not talking about the 4580 output amps here, just the 4x mic input stage). Any ideas?

Dave

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Re: Tascam DR-70D - modification discussion
« Reply #6 on: July 25, 2015, 11:36:17 AM »
How much is the mod?

Jim Williams does not do the mod himself - he modified his own 70D, and then made the details of it free for anyone who wants to do it themselves.  I have posted this on the FAQ page.

You need to find a surface-mount shop to do this for you, so the price will vary.  My shop asked that I source the parts myself as well.  Parts came to $27.06 shipped, and that included one extra opamp and two extra caps just in case.  USPS was $17.90, labor and return shipping $91.00.  All together it ran me $135.96.

Other shops may charge a bit more for labor.  The shop I used said they could charge me a bit less based on what they had learned from doing one of these before.  They don't want to be publicly named, as they don't really have time to do lots of these, sorry.

I think at least one person here has gotten the Busman mod.  I don't know anything about that, as he doesn't advertise it on his website.

Has anyone seen a schematic of the input circuit? I'm very curious, as just two dual (NE5532) opamps to cover four balanced inputs seems a bit low on the 'parts count' (not talking about the 4580 output amps here, just the 4x mic input stage). Any ideas?

Dave

Well as you said they're dual opamps, so each one handles 2 channels.  I have the datasheets linked on the FAQ.  If you look at the pin assignments, there are separate pins for 1IN-, 1IN+, 2IN-, and 2IN+ (+ and - indicating positive and inverted polarity).  So there's your two balanced inputs for each chip.

The data sheet for the LME49270MA (used in the JW mod) shows this much more clearly - see Page 2: http://www.alldatasheet.com/datasheet-pdf/pdf/174239/NSC/LME49720MA.html
« Last Edit: July 25, 2015, 11:38:21 AM by voltronic »
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Offline groovon

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Re: Tascam DR-70D - modification discussion
« Reply #7 on: July 25, 2015, 11:45:11 AM »
How much is the mod?

Jim Williams does not do the mod himself - he modified his own 70D, and then made the details of it free for anyone who wants to do it themselves.  I have posted this on the FAQ page.

You need to find a surface-mount shop to do this for you, so the price will vary.  My shop asked that I source the parts myself as well.  Parts came to $27.06 shipped, and that included one extra opamp and two extra caps just in case.  USPS was $17.90, labor and return shipping $91.00.  All together it ran me $135.96.

Other shops may charge a bit more for labor.  The shop I used said they could charge me a bit less based on what they had learned from doing one of these before.  They don't want to be publicly named, as they don't really have time to do lots of these, sorry.

I think at least one person here has gotten the Busman mod.  I don't know anything about that, as he doesn't advertise it on his website.

Has anyone seen a schematic of the input circuit? I'm very curious, as just two dual (NE5532) opamps to cover four balanced inputs seems a bit low on the 'parts count' (not talking about the 4580 output amps here, just the 4x mic input stage). Any ideas?

Dave

Well as you said they're dual opamps, so each one handles 2 channels.  I have the datasheets linked on the FAQ.  If you look at the pin assignments, there are separate pins for 1IN-, 1IN+, 2IN-, and 2IN+ (+ and - indicating positive and inverted polarity).  So there's your two balanced inputs.

The data sheet for the LME49270MA (used in the JW mod) shows this much more clearly - see Page 2: http://www.alldatasheet.com/datasheet-pdf/pdf/174239/NSC/LME49720MA.html

What you're referring to is just the standard opamp input. All opamps have a differential input (i.e. both an ' inverting' and a 'non-inverting' terminal) but that has nothing necessarily to do with the design of a balanced-input mic (or line) preamp, the better examples of which often use two or more opamps per input in order to improve performance.

(edit) In the case of a design (as here) being limited to one opamp per input, then the opamp is most likely being used in it's most basic form--which is why I'm so curious, given the apparently excellent performance.

Dave
« Last Edit: July 25, 2015, 12:34:44 PM by groovon »

Offline groovon

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Re: Tascam DR-70D - modification discussion
« Reply #8 on: July 25, 2015, 12:28:11 PM »
The problem with using a single opamp stage as a differential input is that it is a trade-off of noise performance vs. input impedance, which has a couple of effects, mainly that it requires larger input capacitors.  If input impedance is increased to allow use of smaller capacitors, then the thermal noise of the input resistors may dominate, potentially reducing or eliminating any benefit from a lower-noise opamp.

Thanks Jon, I was hoping you might be around to fill in some of the finer points. That's pretty much what I was getting at when I referred to the apparently 'minimal' design (of the DR-70 mic pres).

Cases like this make me wonder all over again how much of a part the circuit plays in what we are actually hearing, if even the simplest/compromised(?) design can give such 'unobjectionable' results.

Dave
« Last Edit: July 25, 2015, 12:57:05 PM by groovon »

Offline voltronic

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Re: Tascam DR-70D - modification discussion
« Reply #9 on: July 25, 2015, 12:30:46 PM »
The problem with using a single opamp stage as a differential input is that it is a trade-off of noise performance vs. input impedance, which has a couple of effects, mainly that it requires larger input capacitors.  If input impedance is increased to allow use of smaller capacitors, then the thermal noise of the input resistors may dominate, potentially reducing or eliminating any benefit from a lower-noise opamp.

Would the fact that this unit has digital level control affect this at all?  In a traditional mic input with an analog level control, wouldn't you have a second opamp following the gain pot?  In this case, the opamp is going to a DAC and then DSP for level adjustment.

FWIW, the input impedance of the 70D mic inputs is 2k ohms.  That doesn't seem all that high, but I doubt the input caps are very large in something this small.  I looked up a few others for comparison: the Shure FP24 / MixPre is also 2k, the SD 788 is 3.3k, and the Zoom H6 is way up at 6.8k.
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Re: Tascam DR-70D - modification discussion
« Reply #10 on: July 25, 2015, 12:39:01 PM »
The problem with using a single opamp stage as a differential input is that it is a trade-off of noise performance vs. input impedance, which has a couple of effects, mainly that it requires larger input capacitors.  If input impedance is increased to allow use of smaller capacitors, then the thermal noise of the input resistors may dominate, potentially reducing or eliminating any benefit from a lower-noise opamp.

Would the fact that this unit has digital level control affect this at all?  In a traditional mic input with an analog level control, wouldn't you have a second opamp following the gain pot?  In this case, the opamp is going to a DAC and then DSP for level adjustment.

FWIW, the input impedance of the 70D mic inputs is 2k ohms.  That doesn't seem all that high, but I doubt the input caps are very large in something this small.  I looked up a few others for comparison: the Shure FP24 / MixPre is also 2k, the SD 788 is 3.3k, and the Zoom H6 is way up at 6.8k.

~2k is pretty standard for pro mic inputs. IMO, the question should be, 'how does the actual circuit look', so as we might have a chance of knowing what a mod will likely do, before 'we' do it  ;D

Dave
« Last Edit: July 25, 2015, 12:54:18 PM by groovon »

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Re: Tascam DR-70D - modification discussion
« Reply #11 on: July 25, 2015, 12:54:25 PM »
The problem with using a single opamp stage as a differential input is that it is a trade-off of noise performance vs. input impedance, which has a couple of effects, mainly that it requires larger input capacitors.  If input impedance is increased to allow use of smaller capacitors, then the thermal noise of the input resistors may dominate, potentially reducing or eliminating any benefit from a lower-noise opamp.

Would the fact that this unit has digital level control affect this at all?  In a traditional mic input with an analog level control, wouldn't you have a second opamp following the gain pot?  In this case, the opamp is going to a DAC and then DSP for level adjustment.

FWIW, the input impedance of the 70D mic inputs is 2k ohms.  That doesn't seem all that high, but I doubt the input caps are very large in something this small.  I looked up a few others for comparison: the Shure FP24 / MixPre is also 2k, the SD 788 is 3.3k, and the Zoom H6 is way up at 6.8k.

~2k is pretty standard for pro inputs. IMO, the question should be, 'how does the actual circuit look', so as we might have a chance of knowing what a mod will likely do, before 'we' do it  ;D

Dave

I doubt you're going to get your hands on a schematic, but you could at least take your unit apart and see what you could get from that.  Cheesecadet posted a couple of pictures of his unit, but didn't show the other side of the main board where the opamps for the mic inputs are located:

http://taperssection.com/index.php?topic=172109.msg2131985#msg2131985
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Offline groovon

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Re: Tascam DR-70D - modification discussion
« Reply #12 on: July 25, 2015, 01:07:26 PM »
The problem with using a single opamp stage as a differential input is that it is a trade-off of noise performance vs. input impedance, which has a couple of effects, mainly that it requires larger input capacitors.  If input impedance is increased to allow use of smaller capacitors, then the thermal noise of the input resistors may dominate, potentially reducing or eliminating any benefit from a lower-noise opamp.

Would the fact that this unit has digital level control affect this at all?  In a traditional mic input with an analog level control, wouldn't you have a second opamp following the gain pot?  In this case, the opamp is going to a DAC and then DSP for level adjustment.

FWIW, the input impedance of the 70D mic inputs is 2k ohms.  That doesn't seem all that high, but I doubt the input caps are very large in something this small.  I looked up a few others for comparison: the Shure FP24 / MixPre is also 2k, the SD 788 is 3.3k, and the Zoom H6 is way up at 6.8k.

~2k is pretty standard for pro inputs. IMO, the question should be, 'how does the actual circuit look', so as we might have a chance of knowing what a mod will likely do, before 'we' do it  ;D

Dave

I doubt you're going to get your hands on a schematic, but you could at least take your unit apart and see what you could get from that.  Cheesecadet posted a couple of pictures of his unit, but didn't show the other side of the main board where the opamps for the mic inputs are located:

http://taperssection.com/index.php?topic=172109.msg2131985#msg2131985

I've had the bottom cover off mine a number of times. I may even go further than that now, just out of curiosity. Much can be surmised by following circuit traces--however nothing beats having the actual schematic of the PCB you're looking at.

And yes, I'll bet you're right, that we'll probably never see a proper schematic--as much as I love Tascam for their excellent and (otherwise) highly accessible products :D

That said, I would love it if Tom would prove us both wrong!

Dave
« Last Edit: July 25, 2015, 01:10:20 PM by groovon »

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Re: Tascam DR-70D - modification discussion
« Reply #13 on: July 25, 2015, 01:15:53 PM »
How much is the mod?

I believe there was a post in the other thread that Busman would do his mod for $150 for TS members.  Although we know the specific parts used in the JW mod, I don't believe the parts used in the Busman mod have been described in any detail here. 

I haven't opened up my 70d to look inside.  Wonder how hard it would be to solder the JW mod parts? 

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Re: Tascam DR-70D - modification discussion
« Reply #14 on: July 25, 2015, 02:22:50 PM »
How much is the mod?

I believe there was a post in the other thread that Busman would do his mod for $150 for TS members.  Although we know the specific parts used in the JW mod, I don't believe the parts used in the Busman mod have been described in any detail here. 

I haven't opened up my 70d to look inside.  Wonder how hard it would be to solder the JW mod parts?

Cheesecadet had posted saying that Chris (Busman) mentioned Analog Devices opamps, and that he thinks his mod would sound better, that's about it.  He's selling it, so you can't reasonably expect him to give you all the details.

The opamps are surface-mount, which is much harder to do by hand than regular through-hole components.  I wouldn't even think of attempting it yourself unless you've got lots of experience with such things.  Jon has said he works with surface-mount, he can give you more insight as to why you'd want to have a professional do this kind of work.
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Re: Tascam DR-70D - modification discussion
« Reply #15 on: July 25, 2015, 02:26:01 PM »
Anyone want to take a stab at the before / after files I posted?  I know what I do and don't hear, but would like other opinions.
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Re: Tascam DR-70D - modification discussion
« Reply #16 on: July 25, 2015, 02:41:02 PM »
Anyone want to take a stab at the before / after files I posted?  I know what I do and don't hear, but would like other opinions.

I have only my Sony MDR-V6s right now, but I'll take a stab at it...

Dave

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Re: Tascam DR-70D - modification discussion
« Reply #17 on: July 25, 2015, 03:07:39 PM »
SMT is actually easier to rework once you learn it.  You can simply blow away components with a hot air gun, much less risk of lifting traces.  But you do need a hot air gun and a good soldering iron with a reasonably small, temperature controlled tip.

That's surprising to hear - I was always told that SMT was much more difficult, and that it's harder to find people with the skills to do it by hand. 

I worked a summer job for a couple years in college at an ISO 9001 facility in Woodstock with a lot of military and aerospace contracts.  Out of about a dozen techs doing electronic assembly on the floor, only two were certified for SMT and they wound up working on the most sensitive equipment.  When I asked the supervisors why they didn't use the robotic SMT machines, the answer was that they found the reliability rate was much better with hand assembly which made it worth it for them to put people through the specialized training.
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Re: Tascam DR-70D - modification discussion
« Reply #18 on: July 25, 2015, 03:17:58 PM »
Anyone want to take a stab at the before / after files I posted?  I know what I do and don't hear, but would like other opinions.

OK, I went back and forth a few times. I wouldn't even make a small bet on it, but *just possibly* there's a slight increase in Mid/HF detail in 'B'. I really hesitate to say it though. I'll have another listen sometime.

To be honest I found that both sound somewhat 'veiled' for some reason (and of course there's that hum in the L channel(?) Nice playing though  :D

(edit) Had another listen. I suspect any audible difference between A and B is more likely subtle variations in playing technique than anything else.

Dave
« Last Edit: July 25, 2015, 03:47:13 PM by groovon »

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Re: Tascam DR-70D - modification discussion
« Reply #19 on: July 25, 2015, 04:01:05 PM »
Anyone want to take a stab at the before / after files I posted?  I know what I do and don't hear, but would like other opinions.

OK, I went back and forth a few times. I wouldn't even make a small bet on it, but *just possibly* there's a slight increase in Mid/HF detail in 'B'. I really hesitate to say it though. I'll have another listen sometime.

To be honest I found that both sound somewhat 'veiled' for some reason (and of course there's that hum in the L channel(?) Nice playing though  :D

(edit) Had another listen. I suspect any audible difference between A and B is more likely subtle variations in playing technique than anything else.

Dave

FWIW, I had a hard time hearing the difference on my headphones, but on my monitors it's much easier.  The hum is the DVR hard drive - the mic mount was clamped to my steel TV stand.  Should have thought to unplug it in the first recording, but since I didn't, I left it going for the second recording also.  The "veiled" sound you're hearing in both is because it's an upright piano against a wall.  Again, I don't think this was a great test, but it's what people were asking for, and it's what I could control myself.

Not saying if you guessed right or not; I'll wait for more people to weigh in first.
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Re: Tascam DR-70D - modification discussion
« Reply #20 on: July 25, 2015, 04:12:05 PM »
Anyone want to take a stab at the before / after files I posted?  I know what I do and don't hear, but would like other opinions.

OK, I went back and forth a few times. I wouldn't even make a small bet on it, but *just possibly* there's a slight increase in Mid/HF detail in 'B'. I really hesitate to say it though. I'll have another listen sometime.

To be honest I found that both sound somewhat 'veiled' for some reason (and of course there's that hum in the L channel(?) Nice playing though  :D

(edit) Had another listen. I suspect any audible difference between A and B is more likely subtle variations in playing technique than anything else.

Dave

FWIW, I had a hard time hearing the difference on my headphones, but on my monitors it's much easier.  The hum is the DVR hard drive - the mic mount was clamped to my steel TV stand.  Should have thought to unplug it in the first recording, but since I didn't, I left it going for the second recording also.  The "veiled" sound you're hearing in both is because it's an upright piano against a wall.  Again, I don't think this was a great test, but it's what people were asking for, and it's what I could control myself.

Not saying if you guessed right or not; I'll wait for more people to weigh in first.

I'm also 'guessing' any difference between tracks detectable from this recording is from something other the electronics. Of course, I may be biased  :D

Dave

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Re: Tascam DR-70D - modification discussion
« Reply #21 on: July 25, 2015, 04:22:52 PM »
(edit) Had another listen. I suspect any audible difference between A and B is more likely subtle variations in playing technique than anything else.

Me too.  Taking a wild stab, though, I'll guess B is the mod, based on the faster tempo (new gear excitement and all)... :D

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Re: Tascam DR-70D - modification discussion
« Reply #22 on: July 25, 2015, 11:26:59 PM »
What kind of hot air gun is needed for this?  Or is it so expensive that it's not worth it for this mod?

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Re: Tascam DR-70D - modification discussion
« Reply #23 on: July 26, 2015, 01:08:30 PM »
So, essentially, the mod is not worth the hassle? I've always been amused by the obsession with mods that have little to no real effect. That's not a slam on those who try; that's a cool part of this community.
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Re: Tascam DR-70D - modification discussion
« Reply #24 on: July 26, 2015, 06:08:29 PM »
Is the chipquik smd removal kit a lesser cost option or is a hot air rework station like this essential?  Hate to spend $149 on a station but hate to wreck my recorder.

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Re: Tascam DR-70D - modification discussion
« Reply #25 on: July 26, 2015, 07:00:15 PM »
Is the chipquik smd removal kit a lesser cost option or is a hot air rework station like this essential?  Hate to spend $149 on a station but hate to wreck my recorder.

If you're having to invest anywhere near that much in equipment, you're better off paying a professional who already has said equipment, regardless of how easy it may be do yourself.  I paid less than that for parts, labor, and shipping both ways.  Besides that, if you're not 100% confident in your ability to do this yourself, then you shouldn't do it.  Just my 2 cents.

Since my piano recordings aren't getting many listens it seems, I'd like to try the "pillow test" described by Jon a little while ago.  You've got a set of CM3s - would you mind being the "before" sample?  We can discuss specifics over PM to make this as close as possible.  I can confirm that gain levels are exactly the same post-mod.
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Re: Tascam DR-70D - modification discussion
« Reply #26 on: July 26, 2015, 08:10:08 PM »
PM me with your plan. 


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Re: Tascam DR-70D - modification discussion
« Reply #27 on: July 27, 2015, 11:08:22 AM »
Sort of reminds me of Clint Eastwood saying, ...."do you feel lucky, punk?"    ;D

Jumping back to the question of measuring the stock v. modded unit, is there a way of accurately measuring them by inserting a 150 resistor in an xlr shell, recording to a SDHC card  and then using software like izotope, voxengo, bluecat frequency analyst or does this require an expensive spectrum analyzer? 

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Re: Tascam DR-70D - modification discussion
« Reply #28 on: July 27, 2015, 11:11:25 AM »
Sort of reminds me of Clint Eastwood saying, ...."do you feel lucky, punk?"    ;D

Jumping back to the question of measuring the stock v. modded unit, is there a way of accurately measuring them by inserting a 150 resistor in an xlr shell, recording to a SDHC card  and then using software like izotope, voxengo, bluecat frequency analyst or does this require an expensive spectrum analyzer?

I have RX, and if you look in my dropbox folder, I included screenshots of each file's spectrogram, along with the Waveform Statistics.  There's a Spectrum Analyzer function - I can post those as well.
« Last Edit: July 27, 2015, 11:14:50 AM by voltronic »
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Re: Tascam DR-70D - modification discussion
« Reply #29 on: July 27, 2015, 11:18:48 AM »
Folks... it's time to listen carefully on good headphones to the A v. B samples posted at the top of the thread if you're really interested in the results of the mod. 

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Re: Tascam DR-70D - modification discussion
« Reply #30 on: July 27, 2015, 11:20:21 AM »
Spectrum analysis added to the dropbox folder.
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Re: Tascam DR-70D - modification discussion
« Reply #31 on: July 27, 2015, 12:53:50 PM »
^ This is why 2manyrocks and I have been discussing ways to equalize conditions to separately perform your "pillow test".  We both own CM3s, he has a stock 70D and mine is modified.  I'm proposing going a step further than the pillow by wrapping each mic in a towel first to avoid HF leakage, and then in fleece blankets or acoustic foam, since we both have some.  It's not perfect, but shirt off someone else doing a before and after themselves, it's the best we can get in terms of what you're suggesting.
« Last Edit: July 27, 2015, 12:57:58 PM by voltronic »
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Re: Tascam DR-70D - modification discussion
« Reply #32 on: July 27, 2015, 02:14:39 PM »
Do you and Voltronic both have 70ds and X-Rs by chance?

Did the new firmware seem to you to introduce noise that wasn't present before???  I assume once I upgrade firmware, I can't go back?


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Re: Tascam DR-70D - modification discussion
« Reply #33 on: July 27, 2015, 02:34:43 PM »
Do you and Voltronic both have 70ds and X-Rs by chance?

Did the new firmware seem to you to introduce noise that wasn't present before???  I assume once I upgrade firmware, I can't go back?

I have X-Q; not X-R.

I don't think the firmware update added any noise, at least not that I can hear.  What it did was raise the maximum gain for LOW by 10dB, add the MID range, and raise the minimum gain levels of LOW, HIGH and HIGH+ (although the max levels for those remained the same).  So for the three original gain levels, I suppose you could say that the average gain went up, making any self-noise or mic noise louder than it was before just because it's being amplified more.  For example, at any pot position other than the maximum, the HIGH range is is going to have more gain than it did pre-update.  I have the old / new gain levels listed on the FAQ page.  Just to be clear, those gain levels changed with the 1.10 firmware - not sure what version you were on previously.
« Last Edit: July 27, 2015, 02:39:51 PM by voltronic »
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Re: Tascam DR-70D - modification discussion
« Reply #34 on: July 27, 2015, 03:00:28 PM »
My unit is on 1.10 firmware.

Looks like the gain should be about the same from factory unit to factory unit at the highest end of each gain setting (low, mid, high, high plus)?  Would the gain be different on the modded unit?  (trying to figure out if the gain can be matched between the mod / factory unit without having them both physically side by side)

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Re: Tascam DR-70D - modification discussion
« Reply #35 on: July 27, 2015, 03:10:05 PM »
My unit is on 1.10 firmware.

Looks like the gain should be about the same from factory unit to factory unit at the highest end of each gain setting (low, mid, high, high plus)?  Would the gain be different on the modded unit?  (trying to figure out if the gain can be matched between the mod / factory unit without having them both physically side by side)

If you're on 1.10, then your most recent firmware update made all of the adjustments to the gain levels as I described.  You should update to 1.11, as there are some other fixes in there that they have corrected.

From everything I can tell, the mod did not change gain levels.  I took photos of the knob positions of my unit pre-mod and then matched them exactly post-mod, recording what levels the background noise was reading at as well as the peaks of the music.  Exactly the same before and after. 

I also repeated my open-circuit tests of recording silence at maximum gain for all 4 gain levels.  While I've since learned this is a lousy test to measure noise because it's like you have an infinite resistance on the circuit, I get exactly the same RMS levels on those files pre- and post-mod.
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Re: Tascam DR-70D - modification discussion
« Reply #36 on: July 27, 2015, 04:52:55 PM »
The resistance isn't infinite, it's limited to the input impedance of the device.  So if that's 2K or 10K or whatever, you'd have that much thermal noise at the input.

OK, thanks for correcting me on that.  I may have read that "infinite" thing on GS and assumed it was correct, and you know what happens when you assume...

So for this particular recorder, it's 2k at the XLRs when set to MIC or MIC+PHANTOM; 10k when set to LINE.
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Re: Tascam DR-70D - modification discussion
« Reply #37 on: July 27, 2015, 05:54:04 PM »
All of my mics (except low-sens models) are designed with high output such that preamp noise is not a critical specification.

I just saw this reply.  Yes, when I've run all 4 channels, the X-Qs have a much hotter output (and the expected higher noise) than the CM3s.  I never realized that one of your reasons for making them this way was to make them less dependent on having a very quiet preamp. 

Are you saying that your mics should therefore not be used for a test like this?
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Re: Tascam DR-70D - modification discussion
« Reply #38 on: July 27, 2015, 08:10:16 PM »
OK, to get the ball rolling I stuck my CM3s inside a pile of fleece blankets, ran my long cables to the second bedroom, and recorded 30 seconds at each of the four gain settings with the pots fully up, 48V phantom, 24/96 resolution.  The 70D was also running off my external RavPower USB battery.  Firmware is version 1.11.

The maximum gain levels for each setting are:

HIGH+:  +63 dB
HIGH:    +51 dB
MID:      +36 dB
LOW:    +21 dB

I looked at the files in RX, and found the quietest 15 seconds where there were no intermittent noises and exported those out, which is what is in the dropbox folder below.  There you will also find screenshots of the spectrogram / waveform overlay view, with RX's Waveform Statistics on top of it, as well as the spectral analysis view for each file.

https://www.dropbox.com/sh/wv262wtsca8xhbh/AAC1-wEt-7E5TDTtLIM2JNiga?dl=0

For reference, here are the specs for the CM3 mics.  At 16 dBA self noise, I wonder if these are still too noisy to be useful for this test.  At least these are mics a few of us here own so others can replicate this test on their own.

http://www.lineaudio.se/CM3.html
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Re: Tascam DR-70D - modification discussion
« Reply #39 on: July 27, 2015, 08:36:33 PM »
You need to figure their absolute noise floor:

Sensitivity - 94 + self noise = absolute noise floor

For the CM3, that's -122dBA (maybe -118dBV unweighted).  Not knowing where the stock 70D falls, but going off of the general stats at Avisoft, it's entirely possible that the recorder's EIN is relevant.

Here's a screenshot of that section of the reference manual if it helps:
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Re: Tascam DR-70D - modification discussion
« Reply #40 on: July 27, 2015, 09:26:54 PM »
-120dBu = -122dBV, so that means that EIN is significant for the CM3.  If the weighting measures are roughly equal, total noise would increase by 3dB.

I was with you until this post - I don't understand why knowing the EIN of the recorder tells you anything about if the EIN of this or any other recorder is significant for a particular mic.  Up until this point, I thought that determination would be the absolute noise floor of the mic.  What am I missing?
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Re: Tascam DR-70D - modification discussion
« Reply #41 on: July 27, 2015, 10:18:52 PM »
It is.  If the EIN of the recorder is significant compared with the mic, then system noise will degrade.  It's a root-mean-square calculation, and of course you have to be comparing apples to apples, which means same reference (dBu or dBV) and weighting (A, CCIR, etc.)  As a rule of thumb, you want the recorder EIN to be at least 6dB below microphone noise.  If they are equal, system noise degrades by 3dB.

OK, that last part cleared things up for me.  So what you're saying is to use this mic without adding any noise into the system,  you'd need preamps at a level of quality like the sound devices 7-series that are at -130 dBV or better.  But I suppose that would be true for a lot of other mics and preamps out there.

I'm not sure if you looked at them yet, but are the files and analysis I posted going to be useful, assuming someone else replicates this pretty closely with a stock unit?
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Re: Tascam DR-70D - modification discussion
« Reply #42 on: July 28, 2015, 03:12:56 PM »

Quote
I'm not sure if you looked at them yet, but are the files and analysis I posted going to be useful, assuming someone else replicates this pretty closely with a stock unit?

Yes.  What is interesting is the point at which the noise crosses to flat, which is about 10kHz.  That is better than I would have expected for -122dBV, so the mod could have significantly lower noise.
Well to my ears the noise level before and after hasn't changed, although I wonder if I'm hearing the more of the mic noise and not the preamp.  Jim said at some point that the input transistor noise would dominate at high gain settings, for what that's worth.

What I can tell you is that if I run a spectral analysis on any of my recordings pre-mod, there is a low-level artifact around 22kHz for all 96kHz sample rate recordings, and with 48kHz recordings the artifact moves to around 16kHz and becomes much higher in level.  This is gone post-mod.  See the spectral analysis images of my piano recordings on the first post to see what I mean.  If anyone's paying attention, that gives away the answer to the quiz. :)
« Last Edit: July 28, 2015, 05:45:04 PM by voltronic »
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Re: Tascam DR-70D - modification discussion
« Reply #43 on: July 28, 2015, 05:54:35 PM »
Hard to say exactly what that artifact could have been.  It could have been an interference signal that was present during the original recording.  Both the stock and modified opamps would have sufficiently high PSRR, and the caps added don't do anything about power supply noise or interference.  So either the source of the artifact is not related to the mod, or there was likely another change involved in the mod.

The mention of input transistors could change the noise analysis materially.  Discrete transistors are frequently used as a first-stage in front of an opamp for improved noise performance.  It takes more space though, so you might not see it as often in portable gear.  But it's a cheaper approach than paying for an expensive low-noise opamp (and solves a related problem of input topology).  Since there is gain in the first stage, the noise of the opamp becomes relatively lesser important as first-stage gain increases.

So if the 70D uses that type of input circuit, then opamp noise might not matter except at very low gain where you don't care anyway.

Jon, I'm wondering if you're curious enough yet to get one of these decks and do a tear-down? I'd be very interested in your ideas, and I'm sure many others would too.

Dave
« Last Edit: July 28, 2015, 06:01:22 PM by groovon »

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Re: Tascam DR-70D - modification discussion
« Reply #44 on: July 28, 2015, 06:44:26 PM »
I don't have time, I have a backlog of my own development work.

Yes, I thought might be the case. Otherwise it might be an interesting project.

Dave
« Last Edit: July 28, 2015, 09:43:22 PM by groovon »

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Re: Tascam DR-70D - modification discussion
« Reply #45 on: July 28, 2015, 10:19:02 PM »
Hard to say exactly what that artifact could have been.  It could have been an interference signal that was present during the original recording.  Both the stock and modified opamps would have sufficiently high PSRR, and the caps added don't do anything about power supply noise or interference.  So either the source of the artifact is not related to the mod, or there was likely another change involved in the mod.

The mention of input transistors could change the noise analysis materially.  Discrete transistors are frequently used as a first-stage in front of an opamp for improved noise performance.  It takes more space though, so you might not see it as often in portable gear.  But it's a cheaper approach than paying for an expensive low-noise opamp (and solves a related problem of input topology).  Since there is gain in the first stage, the noise of the opamp becomes relatively lesser important as first-stage gain increases.

So if the 70D uses that type of input circuit, then opamp noise might not matter except at very low gain where you don't care anyway.

There is definitely nothing else done beyond swapping all of the opamps and adding the poly caps.  I took the instructions from Jim, bought the parts myself and sent them off to the SMT shop.  Again, the full details with a parts list are on the FAQ page for those who haven't seen this yet.

Investigating further into this spike I'm seeing: Most, but interestingly not all pre-mod recordings made with the 70D at 48kHz sampling rate have a spike at 15,734 Hz, with the left channel peaking about 10-12 dB higher than the right.  The levels of those peaks I'm seeing are around -63 to -74 dB for the left; -73 to -83 for the right.  This is with HIGH gain setting, typically with the gain 1/3 to 2/3 up.

96 kHz recordings (the very few I have) move that spike up to 21,903 Hz or 21,904 Hz.  I had done a test at this sampling rate recording with my CM3s at max gain for each of the 4 levels, just sitting open on the carpet in a quiet room.  The peak reached as high as -63.5 dB at the HIGH+ gain level, with each of the lower 3 gain levels proportionally lower according to their maximum gain setting.

This pops up in a variety of recording venues.  It's also not the mics, as I analyzed a couple 4-channel recordings that also used the X-Qs and I got the same exact thing, just higher in level.

All recordings I have made with the 70D post-mod do not have this spike at either sample rate.

However, I did find a very small number of recordings with my FP24 > M10 chain also (again using different mics), suggesting either there is something going on with either of those devices which similar to what I'm seeing in the pre-mod 70D, or it's somehow random and environmental as you suggest.

I can't find anything interesting about those two frequencies above 21kHz, but 15,734 Hz is the NTSC horizontal refresh rate.  It would make sense to get that spike if I was ripping the sound from old TV shows...

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Re: Tascam DR-70D - modification discussion
« Reply #46 on: July 29, 2015, 05:22:38 AM »
I suspected the video source pretty quickly when you mentioned 16kHz.  If there is a CRT TV on anywhere nearby, it can cause that.

21kHz could be from a lamp ballast or something.  It's odd that the different sample rates are associated with different interference signals though.

No CRTs anywhere I've recorded recently, and the 96 kHz recordings at home where I got the 21903 Hz spike were all made during the middle of the day with lights off.  Maybe it's just one of those weird random things.
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Re: Tascam DR-70D - modification discussion
« Reply #47 on: July 29, 2015, 09:46:34 AM »
I suspected the video source pretty quickly when you mentioned 16kHz.  If there is a CRT TV on anywhere nearby, it can cause that.

21kHz could be from a lamp ballast or something.  It's odd that the different sample rates are associated with different interference signals though.

No CRTs anywhere I've recorded recently, and the 96 kHz recordings at home where I got the 21903 Hz spike were all made during the middle of the day with lights off.  Maybe it's just one of those weird random things.

Had those spikes too many times. Not just with this recorder and with different mics. Think it is either a battery, cell phone, remote control or some device that has a signal at that rate. It happens at home and at the venues though not all the time. Record at 24/96 and the spike is always over 20000 Hz though did not measure the exact frequency. Run 6 channels sometimes and its only on one set of mics. The same mics do not spike each time. It is like whatever mic/preamp is closest to the source picks it up and the other sets of mics don't. It was random and sometimes I go weeks without it happening then 3-4 show in a row it shows up. No pattern I could ever figure out to what caused it.
« Last Edit: July 29, 2015, 09:56:23 AM by phil_er_up »
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Re: Tascam DR-70D - modification discussion
« Reply #48 on: August 04, 2015, 04:15:11 PM »
Thanks to 2manyrocks, I can now share before / after "pillow test" files and analysis using Line Audio CM3s.  What we each did was stuff our mics in between some pillows / blankets, and record at maximum level for each of the 4 gain settings at 24/96.  I then trimmed each file to the quietest 15 seconds and analyzed with Izotope RX4.

What was very apparent is that while my home appeared quiet on the day I did this, there was a ton of low frequency content being picked up.  In contrast, 2manyrocks had a nice quiet background throughout, with only a slight bass rumble.  You'll see this in the waveform stats and spectrum screenshots. 

When I saw this, I thought we had just wasted our time and the test was invalidated by the drastically different noise floors in our two environments.  But looking closer, the differences were only in the bass.  So in addition to analyzing the files as we recorded them, I also sent everything through a steep 1kHz high-pass filter to level the playing field, and I analyzed those files as well (see the "1kHz HPF" folder).  That was the cutoff where I determined the before/after mod samples sounded the same.

https://www.dropbox.com/sh/wv262wtsca8xhbh/AAC1-wEt-7E5TDTtLIM2JNiga?dl=0

I'm sure some of you will want to examine these files in more detail.  For those that don't, I'll cut to the chase: above 1kHz, the JW-mod unit did not appear to measure any differently than the stock unit for this test.

Thanks to Jon for proposing this idea.
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Re: Tascam DR-70D - modification discussion
« Reply #49 on: August 04, 2015, 06:20:52 PM »
I appreciate your work on this.

I've having a little difficulty remembering how Jim Williams described the effects of his mod, but my hazy recollection is along the lines of improved responsiveness rather than a lowering of the noise floor?  If that's the case, we wouldn't expect to measure a lower noise floor after the mod. 

But how could we test for "improvement" in recording quality?  For example, I have an Adams tuning fork pitch C256.  Would it be possible to record a standard pitch like that and see a difference in the waveform between the modded unit and the stock unit? 

To my hearing, there is a subtle difference between the piano recorded on the stock unit before and after the mod, but how would you measure it?

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Re: Tascam DR-70D - modification discussion
« Reply #50 on: August 04, 2015, 07:06:57 PM »
I appreciate your work on this.

I've having a little difficulty remembering how Jim Williams described the effects of his mod, but my hazy recollection is along the lines of improved responsiveness rather than a lowering of the noise floor?  If that's the case, we wouldn't expect to measure a lower noise floor after the mod. 

But how could we test for "improvement" in recording quality?  For example, I have an Adams tuning fork pitch C256.  Would it be possible to record a standard pitch like that and see a difference in the waveform between the modded unit and the stock unit? 

To my hearing, there is a subtle difference between the piano recorded on the stock unit before and after the mod, but how would you measure it?

Well it would be difficult to measure subjective sound quality differences.  I suppose you could take a stock and modified unit and then make a recording with two very closely matched microphones mounted coincidentally, making a dual-mono recording - one to each recorder, and then compare them like is sometimes done with microphone shootouts.

A tuning fork wouldn't show you all that much.  Maybe something with more pronounced harmonic content and a long decay time, like a large Tibetan prayer bowl, would be a better choice.

Either way, if there are differences, different people may subjectively prefer one or the other.
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Re: Tascam DR-70D - modification discussion
« Reply #51 on: August 04, 2015, 10:30:59 PM »
It's possible the mod is slightly quieter, maybe 0.5dB, with those mics.  I am not sure that 1kHz is an exact point of adjustment, hence the uncertainty.  It could be nothing, or it could be slight.

Again, that is entirely dependent on the mics in question.  Mics with a lower absolute noise floor may show an improvement.

As for other tests, really the best thing you can use are test signals.  There are plenty of sets of test signals available; you can look at squarewaves (make sure those are formed properly for the sample rate used), intermodulation tests that use pairs of HF sine waves, and simple sine waves that look at distortion.  You can also test bursts (impulse response), but those are more interesting for filters, and there are no filters here in question.

Anytime you introduce a real-world complex source the analysis gets so complicated that a listening test will only first determine audibility and second preference.  Those might be interesting, but a measured preference on one source won't necessarily be preferred on another.  The easy-to-saturate transformers I stuck in my boxes are a pretty good example--and there will be no difference in this modification anywhere near as large as that example.

I went by ear on the 1kHz cutoff - it's possible I was too aggressive in setting the filter that high.  The original files are there on that dropbox link if you'd like to try playing with them.
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Re: Tascam DR-70D - modification discussion
« Reply #52 on: August 04, 2015, 11:04:32 PM »
I did analyze the dropbox files using very high-res FFT.

I wasn't questioning your analysis - I meant if you'd like to try a different/better cutoff than the 1kHz I went with.  It probably doesn't matter though, as far as the results for this test are concerned.  As you said, we'd need quieter mics and a more controlled test to find anything further.
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Re: Tascam DR-70D - modification discussion
« Reply #53 on: August 04, 2015, 11:47:04 PM »
Isn't there a way to generate a test signal in audacity or reaper and feed it from a PC into the preamps via a line in?  Should be able to compare the test signal versus the recorded test tone I would think?

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Re: Tascam DR-70D - modification discussion
« Reply #54 on: August 05, 2015, 07:25:16 AM »
Isn't there a way to generate a test signal in audacity or reaper and feed it from a PC into the preamps via a line in?  Should be able to compare the test signal versus the recorded test tone I would think?

Sure, but then you're just testing the line in, which you'd have to set at a pretty low level to not slam the input.
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Re: Tascam DR-70D - modification discussion
« Reply #55 on: August 05, 2015, 09:34:15 PM »
You would be limited to the resolution (THD) of your PC's output.

If you want to test the mic input at high gain, you'd have to pad the output of the PC as well, since it is likely to have lowest THD (and certainly THD+N) near maximum output.

I actually tried this with my stock unit, running from one of the TRS line outputs of my Focusrite interface.  I wasn't trying to measure noise, but was trying to determine the minimum values of the gain pots for each level setting, since that is not in the Tascam specs.  I had to set the monitor volume quite low to avoid brickwalling the 70D inputs when set to MIC, and as a result the recorded signal was quite noisy as Jon indicates.  But it didn't matter for what I was doing - I was able to take the known maximum of each of the 70D gain settings, and lowering the pot slowly until the cutoff point, was able to do some simple math to get the minimum values, which you see on the FAQ page.
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Re: Tascam DR-70D - modification discussion
« Reply #56 on: August 05, 2015, 10:44:54 PM »
Since we've established that this mod doesn't change the self-noise in any significant way, at least with the mics I use, I decided to take the piano comparison recordings and put them both through RX4's Denoise to remove the hum in the background.  I tend to do this with most things I record anyway, as I'm usually recording quiet music in an auditorium with loud HVAC.  Denoise settings were the same for both files; obviously I used different noise profiles but those were nearly identical.

The difference I hear between the stock and modified unit is not changed by the noise reduction, at least not to my ears.  YMMV.  If you didn't hear a difference before, you probably won't hear one now.  Either way, it's at least a bit more pleasant to listen to now.

https://www.dropbox.com/sh/w1d5wujkdhb5fpf/AAAQc7W2XZe1E_4EiphDwMHMa?dl=0
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Re: Tascam DR-70D - modification discussion
« Reply #57 on: August 07, 2015, 09:01:29 PM »
It seems to me that this mod is coming down to the question - "would you prefer to have a modded unit or a non-modded unit?" - which allows for all personal preferences and prejudices and reasons for satisfaction, logical or not, and can't be argued with.  I admire the tenacity, ingenuity and hard work put in by those testing and comparing, however!  It could well have thrown up evidence of major differences, had they been present.

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Re: Tascam DR-70D - modification discussion
« Reply #58 on: August 07, 2015, 10:03:57 PM »
It seems to me that this mod is coming down to the question - "would you prefer to have a modded unit or a non-modded unit?" - which allows for all personal preferences and prejudices and reasons for satisfaction, logical or not, and can't be argued with.  I admire the tenacity, ingenuity and hard work put in by those testing and comparing, however!  It could well have thrown up evidence of major differences, had they been present.

That's a fair assessment.  I think the sample size is far too small and the testing far too limited and compromised to make any kind of definitive judgement though.
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Re: Tascam DR-70D - modification discussion
« Reply #59 on: August 09, 2015, 12:28:40 PM »
It seems to me that this mod is coming down to the question - "would you prefer to have a modded unit or a non-modded unit?" - which allows for all personal preferences and prejudices and reasons for satisfaction, logical or not, and can't be argued with.  I admire the tenacity, ingenuity and hard work put in by those testing and comparing, however!  It could well have thrown up evidence of major differences, had they been present.

That's a fair assessment.  I think the sample size is far too small and the testing far too limited and compromised to make any kind of definitive judgement though.

Having owned a ton of Oade modified gear, I have to say that if your ears like it, it was worth it, specs notwithstanding. Pleasing audio doesn't always relate to specs. You can go nuts trying to justify your mod. I'm pretty sure, for example, that I trade some detail for warmth. I could go with the flow and run a v2 behind my 4022s to bring out the detail, but I tried it and didn't like it for anything for bluegrass. I have zero doubt that the v2 out specs the 148, no offense to Doug. Specs weren't the point to his build I don't think. Same deal with an ad2k vs. a mods m1. Just liked the sound, damn the specs.
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Re: Tascam DR-70D - modification discussion
« Reply #60 on: October 25, 2015, 09:40:25 AM »
I just used my JWMod 70D to record a marching band show for the first time:

http://taperssection.com/index.php?topic=169429.msg2164348#msg2164348

The previous post in that thread is the the same excerpts from the same band at the previous show, where I used FP24 > M10 with a wider spacing.
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Re: Tascam DR-70D - modification discussion
« Reply #61 on: November 12, 2015, 09:41:54 PM »
FYI to any considering a mod (if any such people exist):

While investigating the opamps used in the newly announced DR-701D and comparing against the LME49720MA used in the JWMod for the 70D, I saw that the 49720 has been designated end-of-life, so they will soon be unavailable.  Currently lots in stock at Mouser.
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Re: Tascam DR-70D - modification discussion
« Reply #62 on: November 30, 2015, 07:31:53 PM »
One thing that I am resoundingly unimpressed by is the USB connection for power.

Its nothing about the unit itself...I just hate that flimsy connector...

I never use the USB for transfer - only power.

So - mod wish...some other connector!

I'm fine with losing USB transfer in favor of more robust power connection...since we'll almost always be running this deck off externals.

I know this will mean a custom cable...but I'm ok with that too.
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Re: Tascam DR-70D - modification discussion
« Reply #63 on: November 30, 2015, 08:47:27 PM »
One thing that I am resoundingly unimpressed by is the USB connection for power.

Its nothing about the unit itself...I just hate that flimsy connector...

I never use the USB for transfer - only power.

So - mod wish...some other connector!

I'm fine with losing USB transfer in favor of more robust power connection...since we'll almost always be running this deck off externals.

I know this will mean a custom cable...but I'm ok with that too.

Never thought the microUSB was any flimsier than that same connection on my cell phones or any other things that use it.  I highly recommend a right-angle cable if you're not using one already - doesn't stick out much and feels much more secure.  I have copied the same battery and cable setup recommended by Groovon here, and it's completely solid for me.  The cable stays plugged in except when doing transfers, for which I use the longer cable that came with the 70D.  He actually found this other cable since then which only requires one bend rather than two.  I have stuck with the first one. 

If you're not sticking the battery right underneath the unit and instead have it somewhere else in your bag, you'll want a right-angle microUSB that goes the other way.  When I did that, I used this cable that sticks out and then reaches to another compartment in the bag where the battery lives.

I'm sure some enterprising person could grant your wish and drill a hole to put a hirose connector on this thing, but it seems like way overkill, and the cable will cost as much or more than the battery.
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Re: Tascam DR-70D - modification discussion
« Reply #64 on: November 30, 2015, 09:58:29 PM »
The micro connector, believe it or not, has a higher cycle rating than full size.  I have read complaints from some android tablet users that the micro usb failed after coming loose from the circuit board on their tablets.  I've never seen a similar complaint about the one on the 70d, but it suggests that we ought to be careful about inserting and removing these things.

Low tech and pretty permanent "solution" would be to glue the cable in place.  That urethane stuff they use to hold car windshields or 3m's marine rated adhesive sealant isn't going to turn loose easily.  When the cable goes bad, you'll be cutting it loose with a razor knife.   
« Last Edit: November 30, 2015, 10:09:47 PM by 2manyrocks »

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Re: Tascam DR-70D - modification discussion
« Reply #65 on: December 16, 2015, 09:39:58 PM »
Rather than ask this question in the main thread, I thought I'd ask it here. What does everyone think of the sound of the stock unit? Compared to the M10? Really thinking about getting the Busman mod. My decks been working fine with the PNY Elite and I have so little invested in this thing after selling off SF11, I'm figuring why not get the mod. Even if it isn't a major improvement, I like the way Busman DR70D sounds.  :P

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Re: Tascam DR-70D - modification discussion
« Reply #66 on: December 16, 2015, 10:02:50 PM »
Go for it!!  How much does the mod cost?  I also use a PNY Elite in my deck and it has worked great.  There have been several reports of zero issue with the PNY Elite cards even though they aren't on the approved list. 

Rather than ask this question in the main thread, I thought I'd ask it here. What does everyone think of the sound of the stock unit? Compared to the M10? Really thinking about getting the Busman mod. My decks been working fine with the PNY Elite and I have so little invested in this thing after selling off SF11, I'm figuring why not get the mod. Even if it isn't a major improvement, I like the way Busman DR70D sounds.  :P
« Last Edit: December 16, 2015, 10:04:32 PM by jbell »
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Re: Tascam DR-70D - modification discussion
« Reply #67 on: December 16, 2015, 10:26:19 PM »
I can't speak to the Busman mod, but the total cost for me of the JWMod including parts, labor, and shipping both ways was under $140.  And I'm glad I had it done - I definitely hear an improvement in clarity on the classical recordings I do.  With the stock 70D, I would get better sound with FP24 > M10, but with the mod I think direct into the 70D might now have the edge.  The FP24 can still do higher gain with much lower noise (higher than I ever need though).

See posts 108 and 109 here for samples of the most recent recording I made with my modded deck.
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Re: Tascam DR-70D - modification discussion
« Reply #68 on: December 16, 2015, 11:50:57 PM »
I can't speak to the Busman mod, but the total cost for me of the JWMod including parts, labor, and shipping both ways was under $140.  And I'm glad I had it done - I definitely hear an improvement in clarity on the classical recordings I do.  With the stock 70D, I would get better sound with FP24 > M10, but with the mod I think direct into the 70D might now have the edge.  The FP24 can still do higher gain with much lower noise (higher than I ever need though).

See posts 108 and 109 here for samples of the most recent recording I made with my modded deck.

I have the Busman mod on mine. I've never compared it to a stock unit, but am generally pleased with the sound. Here's a 4 channel mix of the mk41v pair (DIN) and a mk6[figure 8] + mk3 [omni] M/S pair: http://bt.etree.org/details.php?id=583755

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Re: Tascam DR-70D - modification discussion
« Reply #69 on: December 17, 2015, 08:55:01 AM »
Rather than ask this question in the main thread, I thought I'd ask it here. What does everyone think of the sound of the stock unit? Compared to the M10? Really thinking about getting the Busman mod. My decks been working fine with the PNY Elite and I have so little invested in this thing after selling off SF11, I'm figuring why not get the mod. Even if it isn't a major improvement, I like the way Busman DR70D sounds.  :P

The stock unit holds it own with the m10.  Voltronics mod sounds like it smoothed out his piano recording when I listened to it.  Its subtle.  Will have to listen to Noahs when I get time. 

I would only do the mod on a known glitch free unit or get one with busmans warranty. 

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Re: Tascam DR-70D - modification discussion
« Reply #70 on: June 07, 2016, 02:53:48 PM »
I have posted this on the FAQ page.

Where's that FAQ page?

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Re: Tascam DR-70D - modification discussion
« Reply #71 on: June 07, 2016, 05:36:02 PM »
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Re: Tascam DR-70D - modification discussion
« Reply #72 on: June 07, 2016, 06:10:39 PM »
The circuit manual is available?

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Re: Tascam DR-70D - modification discussion
« Reply #73 on: June 07, 2016, 09:51:54 PM »
The circuit manual is available?

If you're talking about a block diagram like you can find at the end of the manuals of some other recorders, then no, it's not published.
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Re: Tascam DR-70D - modification discussion
« Reply #74 on: June 08, 2016, 06:22:52 AM »
No, I mean a service manual with all the schematics.

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Re: Tascam DR-70D - modification discussion
« Reply #75 on: June 08, 2016, 06:40:36 AM »
No, I mean a service manual with all the schematics.

I doubt you'd find one for this recorder; it's not something that's meant to be field serviceable.  You could go ahead and contact Tascam to see what they say.  Just be aware that it's mostly SMT components so you have to be prepared for that sort of work.  I don't have that skill, so I bought the components and then sent mine to a shop that specializes in that kind of work.
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Re: Tascam DR-70D - modification discussion
« Reply #76 on: June 08, 2016, 10:40:19 AM »
No, I mean a service manual with all the schematics.

I doubt you'd find one for this recorder; it's not something that's meant to be field serviceable.  You could go ahead and contact Tascam to see what they say.  Just be aware that it's mostly SMT components so you have to be prepared for that sort of work.  I don't have that skill, so I bought the components and then sent mine to a shop that specializes in that kind of work.

Tom with Tascam provided me the schematics for the hs-p82 when I asked - so I would think he may be able to provide the schematics for most Tascam products
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Re: Tascam DR-70D - modification discussion
« Reply #77 on: June 08, 2016, 10:43:38 AM »
If anyone wants to run some comps with my unit at Phish this summer, get in touch!
Recording:
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Re: Tascam DR-70D - modification discussion
« Reply #78 on: June 08, 2016, 01:10:35 PM »
No, I mean a service manual with all the schematics.

I doubt you'd find one for this recorder; it's not something that's meant to be field serviceable.  You could go ahead and contact Tascam to see what they say.  Just be aware that it's mostly SMT components so you have to be prepared for that sort of work.  I don't have that skill, so I bought the components and then sent mine to a shop that specializes in that kind of work.

Tom with Tascam provided me the schematics for the hs-p82 when I asked - so I would think he may be able to provide the schematics for most Tascam products

Do you have an email for him?  He has flown the coop from TS but I occasionally see him post at JWSound.
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Re: Tascam DR-70D - modification discussion
« Reply #79 on: June 08, 2016, 05:08:53 PM »
From what I've seen, the components involved in the mod are not that small. The 49720 is just 5mm long, and you have just to know how to solder. The original 5532s you just cut away carefully. The caps are a breeze to add.

But what got me curious about the schematics was the comment on your page that "Limiter adds 12dB noise and should be avoided".

Some time ago I saw the 680 schematics, and the limiter was praised for its quality. so I wonder why didn't they use it on the 70.

 

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Re: Tascam DR-70D - modification discussion
« Reply #80 on: June 08, 2016, 10:33:50 PM »
From what I've seen, the components involved in the mod are not that small. The 49720 is just 5mm long, and you have just to know how to solder. The original 5532s you just cut away carefully. The caps are a breeze to add.

But what got me curious about the schematics was the comment on your page that "Limiter adds 12dB noise and should be avoided".

Some time ago I saw the 680 schematics, and the limiter was praised for its quality. so I wonder why didn't they use it on the 70.

Well, clearly you have much more experience in electronics assembly than I do, which is why I sent mine out.

As for the 680 limiter, that recorder costs twice as much as the 70D, so I'm not surprised compromises were made.  I'm fairly certain that the 680 is still a digital limiter though.
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Re: Tascam DR-70D - modification discussion
« Reply #81 on: June 10, 2016, 07:16:19 PM »
I am aware of the price of the 680. But it's also a much more complete design, much larger too.

In fact it's closer in price to the DR701, which has some similar capabilities in a smaller package. Comparison tests should be in order.

The limiter is probably the same on all Tascam models, and yes, it's digital. But I wonder why it introduces noise on the 70 and not on the other models.

Now there's a 680 Mark II, but the mic preamps are probably the same HDDA types than on the 70, with 5532 chips.

Interesting the chip selected by Jim for the mod, as a much better one, lower noise could be used: the NJM2068. I've already mailed him to ask the reasons for his choice.




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Re: Tascam DR-70D - modification discussion
« Reply #82 on: June 10, 2016, 07:56:10 PM »
I am aware of the price of the 680. But it's also a much more complete design, much larger too.

In fact it's closer in price to the DR701, which has some similar capabilities in a smaller package. Comparison tests should be in order.

That's exactly my point - they had a larger size case and a larger price point in which to work, so the 680 should be a design with fewer compromises made.

Quote
The limiter is probably the same on all Tascam models, and yes, it's digital. But I wonder why it introduces noise on the 70 and not on the other models.

Now there's a 680 Mark II, but the mic preamps are probably the same HDDA types than on the 70, with 5532 chips.

Hopefully someone with more knowledge on this will chime in here, but from my understanding the limiter on the 70D is after the ADC and at some point within there lowers the gain 12dB, then later raises it back up to the original level after applying the limiting in a way the brings the internal noisefloor up 12dB along with it.

Quote
Interesting the chip selected by Jim for the mod, as a much better one, lower noise could be used: the NJM2068. I've already mailed him to ask the reasons for his choice.

??? Are you sure you aren't looking at a different chip?  Jim's mod uses the LME49720.  THD+N is 0.00003%, vs. your recommendation of the NJM2068 at 0.001%.  The 49720 also has a much higher slew rate: 20V/us, vs. 6V/us for the 2068.  Finally, the 49720 also has nearly twice the gain bandwidth: 55 MHz vs. 27 MHz.  Now, there are many out there that say none of that really matters and that either are more than good enough for this application, but the 49720 looks like a superior part in all respects.
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Re: Tascam DR-70D - modification discussion
« Reply #83 on: June 10, 2016, 09:59:06 PM »
Sorry, I mixed up the chips. The NJM ultra low noise chip is the NJM2122.

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Re: Tascam DR-70D - modification discussion
« Reply #84 on: June 10, 2016, 10:28:08 PM »
Sorry, I mixed up the chips. The NJM ultra low noise chip is the NJM2122.

Well, the NJM2122 is worse still.  Just comparing 3 of the specs:

                            LME49720           NJM2068           NJM2122

THD+N                 0.00003%           0.001%            0.003%
Slew Rate            20 V/μs                6 V/μs              2.4 V/μs
Gain Bandwidth   55 MHz                27 MHz             12 MHz
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Re: Tascam DR-70D - modification discussion
« Reply #85 on: June 10, 2016, 10:49:02 PM »
Because the input noise would be dominated by the discrete input transistors below a certain noise level for the opamp.  It's questionable whether a change from 5532 even results in lower EIN.  See posts #57-58.

I thought it was the other way around; that the input transistors were the biggest contributor of noise at high gain levels.  Maybe I misunderstood.  Either way, the highest gain setting (HIGH+) on this unit is not useful for music recording, and that hasn't changed post-mod.

Not to go through this all again, but the modification did not reduce the self-noise in any way I can detect.  What it definitely did do was improve the HF clarity / extension, but again I wonder if the added caps have more to do with that than the opamps.

Curious that TI does not list a THD spec for the 5532.
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Re: Tascam DR-70D - modification discussion
« Reply #86 on: June 11, 2016, 04:49:51 AM »
cool discussion! I have no personal experience with the modded 70D except listening to Noah's/Voltronic's modded units, and like they said, the difference is very subtle at best to me, BUT I have never heard a direct COMP between a modded and unmodded 70d! Noah and I ran on the same stand@PH MPP last year[I ran mk4>pfa>70d + mk41>VMS02IB>70d and he ran mk41v>pfa>busman modded 70d + mk22>pfa>70d], so not really a direct comp! If anyone wants links to my PH/MPP Night 2 from 2015, just LMK! I have the show on my Google Drive acct already ;)

That said Carlos, I think you should get your 70d and try it stock first, before doing the mod. But that's just my opinion :) I have run mk4>pfa>70d preamps numerous times, and I think that the 70d preamps are quite adequate for use with low-noise condenser mics like my Schoeps and many other brands, as long as you aren't using the High/High+ gain on the 70d like Voltronic said. I have only used LOW or MID for field recording[LOW being enough gain for me 90% of the time] with my Schoeps caps, with great success :) However, I would really like to hear a DIRECT COMP between the modded 70d vs. a stock 70d unit, because in the end I want to get all that I can out of my 70d's, and if that means changing some opamps/caps, then I'm all for it 8) Especially since I only paid $300 total for BOTH of my 70d's :P ;D So If its a cheap way to improve the 70d even further and extend the HF range a bit, then like I said, I'm ALL for it ;) I just don't want the HF's to be grating and fatiguing or the lowend affected AFTER the opamp/Cap mod, when it could've been avoided by leaving the 70d stock, that's all :) I guess someone just needs to do a correct COMP so we can hear for ourselves if getting the mod is "worth it" or not? :)

Noah, you still have seeders on any of your PH sources up on etree with your Busman modded 70d ??? I can provide my mk4>pfa>70d source if you can provide your mkxx>pfa>Busman modded 70d sources for Phish/MPP Night 2[8.16.2015] ;)
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Re: Tascam DR-70D - modification discussion
« Reply #87 on: June 11, 2016, 07:03:48 AM »
I agree that you should get a bunch of recordings in with the stock unit before you decide on modding it.  And you'll probably never hear the difference if you're doing amplified shows.  I notice the effect of the mod on the acoustic recording I'm doing, particularly with the attack of percussion and strings and consonants in voices, and also on the quality of the reverb in a hall with good acoustics.

2manyrocks and I tried to do a long-distance comp of self noise since we have some of the same mics, but that didn't work out.  Do do a true comp, you probably need a mic splitter box so one set of mics is feeding the two 70Ds recording the same concert.
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Re: Tascam DR-70D - modification discussion
« Reply #88 on: June 14, 2016, 01:30:40 PM »
No, I won't touch my 70D until I make many recordings, some of them using the line input and external mixer or preamp.

Even so, I think the line input may not bypass the mic input, just attenuating the signal.


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Re: Tascam DR-70D - modification discussion
« Reply #89 on: June 14, 2016, 04:23:02 PM »
Even so, I think the line input may not bypass the mic input, just attenuating the signal.

I think you asked about this already, and it's likely exactly how you said.

Be advised that there are different opamps for the 1/8" line in/outs than there are for the 4 XLR-1/4" combo jacks.
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Re: Tascam DR-70D - modification discussion
« Reply #90 on: August 20, 2016, 03:45:09 AM »
Can anyone who has gotten the Busman MOD to their DR-70D, please tell me how much it costs to get all 4 channels done and the opamps switched out and everything? Isn't Noah's DR-70D Busman modded? Since I have [2] 70D's, I was thinking of getting one of them modded this winter by Busman, and A/B the stock vs Busman 70D's, and see which I prefer! The Busman MOD might benefit my PFA->70D rig more, while the stock 70D be better suited for when I run my VMS->70D!

TIA,
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Re: Tascam DR-70D - modification discussion
« Reply #91 on: August 20, 2016, 07:21:52 AM »
I don't know anything about the Busman mod, but I can tell you that the total cost for me to do the Jim Williams mod was $136, including return shipping.  All of my recordings posted here with 4061s have been through PFAs into the modded 70D, FWIW.

When you're deciding what to mod or not, it's worth asking Busman what is and is not modded.  The JW Mod affects the 4 combo inputs as well as the 3.5 mm line inputs and outputs.
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Re: Tascam DR-70D - modification discussion
« Reply #92 on: August 20, 2016, 08:11:48 AM »
Thanks Volt +T 8)
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Re: Tascam DR-70D - modification discussion
« Reply #93 on: August 22, 2016, 09:44:04 AM »
I have had mine modded by Busman, here is what was on the invoice and price when mine was done about 5 months ago.

Tascam DR70 modifications
replacement of op amps and capacitors in input path. replacement of op amps for line in and headphone out as well.   1   $150.00   $150.00


I haven't ran my Mini-MP since having the mod done, love the sound with my KM184's.  If I can get caught up with work I will try to put some shows up with the combo.
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Re: Tascam DR-70D - modification discussion
« Reply #94 on: August 22, 2016, 01:26:56 PM »
I have had mine modded by Busman, here is what was on the invoice and price when mine was done about 5 months ago.

Tascam DR70 modifications
replacement of op amps and capacitors in input path. replacement of op amps for line in and headphone out as well.   1   $150.00   $150.00


I haven't ran my Mini-MP since having the mod done, love the sound with my KM184's.  If I can get caught up with work I will try to put some shows up with the combo.

In that case it sounds very similar to the JW Mod in what was done, but I'm sure with different parts being used.  I think someone here at one point mentioned Busman was using Analog Devices opamps, for instance.
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Re: Tascam DR-70D - modification discussion
« Reply #95 on: August 22, 2016, 11:35:01 PM »
I have had mine modded by Busman, here is what was on the invoice and price when mine was done about 5 months ago.

Tascam DR70 modifications
replacement of op amps and capacitors in input path. replacement of op amps for line in and headphone out as well.   1   $150.00   $150.00


I haven't ran my Mini-MP since having the mod done, love the sound with my KM184's.  If I can get caught up with work I will try to put some shows up with the combo.

+T Thanks for the info 8) I think that $150 is DEF a fair price for having that done IMO! I'll prob get Busman to MOD mine this fall/winter, and mainly use the Busman MOD 70D with my PFA>70d rigs and as my main 70d :) And I will have the stock 70D to COMP against! I'll just run mk4/41->kcy->PFA->Splitters->Busman 70D + Stock 70D and see which I prefer!
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Re: Tascam DR-70D - modification discussion
« Reply #96 on: August 29, 2016, 06:15:31 PM »
I don't know anything about the Busman mod, but I can tell you that the total cost for me to do the Jim Williams mod was $136, including return shipping.  All of my recordings posted here with 4061s have been through PFAs into the modded 70D, FWIW.

When you're deciding what to mod or not, it's worth asking Busman what is and is not modded.  The JW Mod affects the 4 combo inputs as well as the 3.5 mm line inputs and outputs.

Voltronic so opinion is if your tape/record AC/DC or that type 90DB Plus Kind Of P.A. the mod is not necessary.
been thinking about getting a 70D.

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Re: Tascam DR-70D - modification discussion
« Reply #97 on: August 29, 2016, 07:56:08 PM »
I don't know anything about the Busman mod, but I can tell you that the total cost for me to do the Jim Williams mod was $136, including return shipping.  All of my recordings posted here with 4061s have been through PFAs into the modded 70D, FWIW.

When you're deciding what to mod or not, it's worth asking Busman what is and is not modded.  The JW Mod affects the 4 combo inputs as well as the 3.5 mm line inputs and outputs.

Voltronic so opinion is if your tape/record AC/DC or that type 90DB Plus Kind Of P.A. the mod is not necessary.
been thinking about getting a 70D.

Any mod would be a waste of money for anyone doing stack recording of loud rock, in my opinion.  Others here will say it's a waste of money period, but it made an audible difference in my recordings (acoustic / classical / choral).
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Re: Tascam DR-70D - modification discussion
« Reply #98 on: August 30, 2016, 10:01:17 AM »
Really love this as a backup deck. Sips batteries and is reliable. Only downside, as we all know, is the level knobs are easily moved. Anyone figure out a way to fix that? Rubber band?
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Re: Tascam DR-70D - modification discussion
« Reply #99 on: August 30, 2016, 05:06:03 PM »
Really love this as a backup deck. Sips batteries and is reliable. Only downside, as we all know, is the level knobs are easily moved. Anyone figure out a way to fix that? Rubber band?

Set levels, engage hold switch?
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Re: Tascam DR-70D - modification discussion
« Reply #100 on: August 30, 2016, 07:36:04 PM »
I did that but the hold function worries me as you potentially could power down the deck by pushing the button down too hard, no?
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Re: Tascam DR-70D - modification discussion
« Reply #101 on: August 30, 2016, 10:05:53 PM »
I did that but the hold function worries me as you potentially could power down the deck by pushing the button down too hard, no?

Hold is in the opposite direction.  There's no risk of powering down accidentally while engaging hold.  I use it for every concert and have never had an issue.

What does this have to do with a modded deck?  Seems more suited to the regular discussion thread, since those who have no interest in the mods probably ignore this thread
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Re: Tascam DR-70D - modification discussion
« Reply #102 on: August 30, 2016, 11:13:25 PM »
Disengaging hold is a downward motion, toward off, which is my point about risking shutting down the deck.

Apologies to all of you who had to suffer through this radical detour from internal mods.
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Re: Tascam DR-70D - modification discussion
« Reply #103 on: August 31, 2016, 06:00:41 AM »
Disengaging hold is a downward motion, toward off, which is my point about risking shutting down the deck.

Apologies to all of you who had to suffer through this radical detour from internal mods.

Oh, I thought you were worried about engaging hold.  The good news is that you have to hold power for quite a while to get it to turn off, so I still don't think there's much risk of this happening accidentally.
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Re: Tascam DR-70D - modification discussion
« Reply #104 on: August 31, 2016, 06:32:59 PM »
Disengaging hold is a downward motion, toward off, which is my point about risking shutting down the deck.
The good news is that you have to hold power for quite a while to get it to turn off, so I still don't think there's much risk of this happening accidentally.

I counted about a two-second delay before powering down.

Compare this to approx 3.5 seconds to get the display to light up when powering up!?!

Ain't that weird? I don't blame VWMULE for being a bit worried, but as long as you feel it click off of hold and then you let it go, you'll be fine.
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Re: Tascam DR-70D - modification discussion
« Reply #105 on: August 31, 2016, 07:38:21 PM »
Disengaging hold is a downward motion, toward off, which is my point about risking shutting down the deck.
The good news is that you have to hold power for quite a while to get it to turn off, so I still don't think there's much risk of this happening accidentally.

I counted about a two-second delay before powering down.

Compare this to approx 3.5 seconds to get the display to light up when powering up!?!

Ain't that weird? I don't blame VWMULE for being a bit worried, but as long as you feel it click off of hold and then you let it go, you'll be fine.

Emphasis on that key point above.  Trust the tactile feedback.  Trust your feelings, Luke.   That's how I do it on the M10, and the hold/power switch has far less travel than the 70D. 
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Re: Tascam DR-70D - modification discussion
« Reply #106 on: September 01, 2016, 01:08:36 AM »
Never been an issue for me either!
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Re: Tascam DR-70D - modification discussion
« Reply #107 on: September 01, 2016, 08:18:06 AM »
Unless you must have four channels, does the mkiii dr100 undercut the mod? Tascam is promoting the new dr100 mkiii as their flagship at $399, you get their factory warranty, and the display looks like it would be much better for monitoring levels.

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Re: Tascam DR-70D - modification discussion
« Reply #108 on: September 01, 2016, 06:46:31 PM »
Unless you must have four channels, does the mkiii dr100 undercut the mod? Tascam is promoting the new dr100 mkiii as their flagship at $399, you get their factory warranty, and the display looks like it would be much better for monitoring levels.

It very well might.  Tascam is telling us nothing about the preamps in the 100 other than it uses "HDDA" preamps, which is just the same marketing BS used with the 70D and 701D.  In the case of those two units, they did at least mention which opamps were being used, and those in the 701D are much better than those in the 70D, almost as good as the TI chips used in the JWMod.  Not to say the opamp by itself tells you everything about the preamp section.

For the 100 they appear to be pushing the quality of the ADC as a big selling point; no details on the preamps.

It's worth noting that EIN, distortion and S/N of the DR-100mkIII look excellent, almost equal that of the DR-701D so we might assume they use the same preamps.

Long story short, if I definitely only needed 2 channels I'd probably by the 100mkIII.  If you need 4 P48 inputs, I think the 70D with or without the mod is still an excellent value.
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Re: Tascam DR-70D - modification discussion
« Reply #109 on: September 02, 2016, 12:56:18 AM »
A taper friend of mine just bought and already got a 701D a few days ago 8) Said it has a nice solid feel[magnesium alloy chassis vs plastic], and it basically has every feature that we wanted for the 70D in future FW updates lol and a cooler blue screen :P ;D I wish I had more on my taping schedule, because I'd borrow it[he did offer] and give it a test run right next to a stock 70D and split my PFA OUTS :)

And as far as just doing 2 channel, the 100mkiii def looks like a cool & solid deck for the $$! But for around at least $100 less, you can get a 70D with 4 XLR INS, so its really up to your individual needs and wants!
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Re: Tascam DR-70D - modification discussion
« Reply #110 on: September 02, 2016, 10:59:39 AM »
I'd be curious whether the mod and firmware requests for the 70d influenced tascam in the development of the 701d. 

The continuation of the dr100mkiii surprised me.  I would have expected tascam to drop it given the offering of the 701d.  It also surprises me to see them continue to use the menu wheel and to continue the internal lit ion batteries instead of just as batteries and an external 5v battery.  But I suppose they've got to have lit ion batteries to attain a reasonable run time. 

 


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Re: Tascam DR-70D - modification discussion
« Reply #111 on: September 03, 2016, 04:28:47 PM »
Voltronic where did you buy 5 of these??  LME49720MA op amp the link in the fact page only allows you to buy 90 at a time. 
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Re: Tascam DR-70D - modification discussion
« Reply #112 on: September 03, 2016, 08:46:52 PM »
Voltronic where did you buy 5 of these??  LME49720MA op amp the link in the fact page only allows you to buy 90 at a time.

I bought everything from Mouser.  There was no quantity minimum when I purchased.
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Re: Tascam DR-70D - modification discussion
« Reply #113 on: May 13, 2017, 08:50:16 PM »
Hi guys. I'm new here. i intent to buy this recorder to record church events.

but i have one problem: i was thinking in using as a "in the middle" device, like connecting up to 4 mic's on it, and EACH mic output of the 70D in the mixer, so they can adjust independently each input, and i record "mine" in the middle without messing their audio setup (mics > 70D > mixer line-in for each channel)

but as you know, the 70D does not have independent outputs for each mic, only a line-out (i believe it mixes the 4 channels to 2 channels).

so, as i have a basic knowledge on op-amps and electronics, my question: technically, i can add extra op-amps to get the output from the mic pre-amps and make 4 outputs using the op-amps in "voltage follower" mode? (just to get an "extra" output for each channel)

or i can use the internal line-out op-amps (i assume it uses extra op-amps to mix the outputs) to get 4 outs instead of 2 mixed outs?

another thing: anyone knows the power section of this device? what voltages it uses internally? i may mod to use li-ion instead of AA's

thanks in advance!!!

OBS: I'm Brazilian, sorry for the poor english!  :cheers:

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Re: Tascam DR-70D - modification discussion
« Reply #114 on: May 14, 2017, 07:56:44 AM »
Hi guys. I'm new here. i intent to buy this recorder to record church events.

but i have one problem: i was thinking in using as a "in the middle" device, like connecting up to 4 mic's on it, and EACH mic output of the 70D in the mixer, so they can adjust independently each input, and i record "mine" in the middle without messing their audio setup (mics > 70D > mixer line-in for each channel)

but as you know, the 70D does not have independent outputs for each mic, only a line-out (i believe it mixes the 4 channels to 2 channels).

so, as i have a basic knowledge on op-amps and electronics, my question: technically, i can add extra op-amps to get the output from the mic pre-amps and make 4 outputs using the op-amps in "voltage follower" mode? (just to get an "extra" output for each channel)

or i can use the internal line-out op-amps (i assume it uses extra op-amps to mix the outputs) to get 4 outs instead of 2 mixed outs?

another thing: anyone knows the power section of this device? what voltages it uses internally? i may mod to use li-ion instead of AA's

thanks in advance!!!

OBS: I'm Brazilian, sorry for the poor english!  :cheers:

So, you want to be able to record 4 channels, but then also have 4 independent line outputs?  I have no idea if the modification you're proposing is possible or not.  But either way, it seems that what you want to do would be so much easier with a good analog mixer, where you can easily route any channel to any subgroup or aux output.

I don't understand why you'd want to do something like this with the 70D.
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Re: Tascam DR-70D - modification discussion
« Reply #115 on: May 14, 2017, 08:31:19 AM »
So, you want to be able to record 4 channels, but then also have 4 independent line outputs?  I have no idea if the modification you're proposing is possible or not.  But either way, it seems that what you want to do would be so much easier with a good analog mixer, where you can easily route any channel to any subgroup or aux output.

I don't understand why you'd want to do something like this with the 70D.

cause i want separated audio tracks for easy editing and flexibility. and because events already have a mixer. also i tested a few mixers, and i found them very noisy.

also, one device that do all is better and cheaper than two ;)

i was about to get a behringer umc404hd (usb audio interface, 4 input that have 4 outputs, one for each mic) for this purpose. but a device like the 70D now seems much more complete, just missing this feature ;)
« Last Edit: May 14, 2017, 09:47:45 AM by malow »

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Re: Tascam DR-70D - modification discussion
« Reply #116 on: May 14, 2017, 10:16:45 AM »
So, you want to be able to record 4 channels, but then also have 4 independent line outputs?  I have no idea if the modification you're proposing is possible or not.  But either way, it seems that what you want to do would be so much easier with a good analog mixer, where you can easily route any channel to any subgroup or aux output.

I don't understand why you'd want to do something like this with the 70D.

cause i want separated audio tracks for easy editing and flexibility. and because events already have a mixer. also i tested a few mixers, and i found them very noisy.

also, one device that do all is better and cheaper than two ;)

i was about to get a behringer umc404hd (usb audio interface, 4 input that have 4 outputs, one for each mic) for this purpose. but a device like the 70D now seems much more complete, just missing this feature ;)

Why not just get a used Tascam DR680? It has dedicated outputs and there might be quite a few on the market since the intro of the SD MixPre-6.


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Re: Tascam DR-70D - modification discussion
« Reply #117 on: May 14, 2017, 10:49:48 AM »
Why not just get a used Tascam DR680? It has dedicated outputs and there might be quite a few on the market since the intro of the SD MixPre-6.

looks like would be nice for what i want. but used cost more than twice the 70D...  :(

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Re: Tascam DR-70D - modification discussion
« Reply #118 on: May 14, 2017, 11:41:20 AM »
Why not just get a used Tascam DR680? It has dedicated outputs and there might be quite a few on the market since the intro of the SD MixPre-6.

looks like would be nice for what i want. but used cost more than twice the 70D...  :(

Here you go:

http://taperssection.com/index.php?topic=181808.msg0#new

Terrific deal! (No affiliation.)
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Re: Tascam DR-70D - modification discussion
« Reply #119 on: May 14, 2017, 12:30:09 PM »
Here you go:

http://taperssection.com/index.php?topic=181808.msg0#new

Terrific deal! (No affiliation.)

it would be nice... if i were an american...  :shrug:

in brazil US$ to BR$ is 3.5x the value, plus 60% to 100% import taxes (over the price with shipping), so in the end will cost a kidney. i can only buy locally.  :-[

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Re: Tascam DR-70D - modification discussion
« Reply #120 on: May 14, 2017, 12:37:48 PM »
Here you go:

http://taperssection.com/index.php?topic=181808.msg0#new

Terrific deal! (No affiliation.)

it would be nice... if i were an american...  :shrug:

in brazil US$ to BR$ is 3.5x the value, plus 60% to 100% import taxes (over the price with shipping), so in the end will cost a kidney. i can only buy locally.  :-[

I sympathize with your problem. Our Canadian dollar is unconscious at the bottom of the swimming pool. In my case, it's making a new SD MixPre-6 out of reach.
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Re: Tascam DR-70D - modification discussion
« Reply #121 on: May 15, 2017, 04:42:47 PM »
So, you want to be able to record 4 channels, but then also have 4 independent line outputs?  I have no idea if the modification you're proposing is possible or not.
I don't understand why you'd want to do something like this with the 70D.

cause i want separated audio tracks for easy editing and flexibility. and because events already have a mixer. also i tested a few mixers, and i found them very noisy.

also, one device that do all is better and cheaper than two ;)

i was about to get a behringer umc404hd (usb audio interface, 4 input that have 4 outputs, one for each mic) for this purpose. but a device like the 70D now seems much more complete, just missing this feature ;)

If you want 4 separated audio tracks for editing, you will get that with the DR70d. All you have to do is take out the SD card and put it into a PC tablet or laptop and you will have all the channels ready for editing. Plus that is much quicker than using an analog output.
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Re: Tascam DR-70D - modification discussion
« Reply #122 on: May 15, 2017, 04:49:37 PM »
If you want 4 separated audio tracks for editing, you will get that with the DR70d. All you have to do is take out the SD card and put it into a PC tablet or laptop and you will have all the channels ready for editing. Plus that is much quicker than using an analog output.

You also eliminate a stage of D/A conversion by using the information on the card to import the digital file to your DAW.

Offline voltronic

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Re: Tascam DR-70D - modification discussion
« Reply #123 on: May 15, 2017, 07:23:58 PM »
So, you want to be able to record 4 channels, but then also have 4 independent line outputs?  I have no idea if the modification you're proposing is possible or not.
I don't understand why you'd want to do something like this with the 70D.

cause i want separated audio tracks for easy editing and flexibility. and because events already have a mixer. also i tested a few mixers, and i found them very noisy.

also, one device that do all is better and cheaper than two ;)

i was about to get a behringer umc404hd (usb audio interface, 4 input that have 4 outputs, one for each mic) for this purpose. but a device like the 70D now seems much more complete, just missing this feature ;)

If you want 4 separated audio tracks for editing, you will get that with the DR70d. All you have to do is take out the SD card and put it into a PC tablet or laptop and you will have all the channels ready for editing. Plus that is much quicker than using an analog output.

That was my thinking also.  No need to complicate this any further.
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Offline dogmusic

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Re: Tascam DR-70D - modification discussion
« Reply #124 on: May 15, 2017, 08:39:42 PM »
So, you want to be able to record 4 channels, but then also have 4 independent line outputs?  I have no idea if the modification you're proposing is possible or not.
I don't understand why you'd want to do something like this with the 70D.

cause i want separated audio tracks for easy editing and flexibility. and because events already have a mixer. also i tested a few mixers, and i found them very noisy.

also, one device that do all is better and cheaper than two ;)

i was about to get a behringer umc404hd (usb audio interface, 4 input that have 4 outputs, one for each mic) for this purpose. but a device like the 70D now seems much more complete, just missing this feature ;)

If you want 4 separated audio tracks for editing, you will get that with the DR70d. All you have to do is take out the SD card and put it into a PC tablet or laptop and you will have all the channels ready for editing. Plus that is much quicker than using an analog output.

That was my thinking also.  No need to complicate this any further.

My understanding was that the poster wanted the four outputs for a live recording situation, not to edit the recordings afterwards. From his initial post:

 "i intent to buy this recorder to record church events.... i was thinking in using as a "in the middle" device, like connecting up to 4 mic's on it, and EACH mic output of the 70D in the mixer, so they can adjust independently each input, and i record "mine" in the middle without messing their audio setup (mics > 70D > mixer line-in for each channel)"

So there's a setup at a church where four mics are being fed into a mixer. The poster wants to put his recorder in-between the mics and the mixer, i.e., use their setup without disturbing it.

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Re: Tascam DR-70D - modification discussion
« Reply #125 on: May 16, 2017, 03:57:00 PM »
Why not use a mixer with direct outputs on the channels, and run mics > mixer > direct outs > DR70D

If the mixer doesn't have them, I'd bet that it's easier to modify that, than the DR70D!
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Offline dogmusic

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Re: Tascam DR-70D - modification discussion
« Reply #126 on: May 16, 2017, 05:36:00 PM »
Why not use a mixer with direct outputs on the channels, and run mics > mixer > direct outs > DR70D

If the mixer doesn't have them, I'd bet that it's easier to modify that, than the DR70D!

Or he could make up a set of four splitters from the mics, sending the feed simultaneously to the mixer and the DR70D. Use the phantom power on the mixer only.
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Offline ScoobieKW

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Re: Tascam DR-70D - modification discussion
« Reply #127 on: May 17, 2017, 12:16:05 AM »
1:1 isolation transformers on each split channel.

This way there is no way for double phantom to reach the mics. House engineers are much more friendly to gear that has no chance of messing with their show/equipment.

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Offline malow

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Re: Tascam DR-70D - modification discussion
« Reply #128 on: May 17, 2017, 03:03:47 AM »
i may not have explained in the best way, but dogmusic got it.

some churches have a great modern mixer, some have a tiny mixer, some not even a "rec out" connector, and some does not even have a mixer or usable sound system (one once had a very very old wooden box with mic's input, a volume knob, and speaker connector. THAT'S IT. nothing else.

so, as even the ancient systems use the standards mic's connectors (XLR or TRS), i realized the only way to guarantee i will be able to get the audio in any church, is to get the audio from the mic's itself.

but, of course, i also need to send the mic's audio "i stole" to the church sound system, so my idea of using the 70D recorder to get individual recordings of each mic (a must for me) and also send each to the church sound system (also send individually)

but, now you guys mentioned mic splitters (something i didn't know existed) looks like another option. i found locally only a few models, not cheap, but is a good option ;)

one thing: as the splitter uses a tranformer(passive ones) this will cause a few dB drops, correct? as any transformer, it have some resistance added directly to the signal, right?

also, second thing: if splitters use a "audio" transformer with 1:1 ratio, its not the same kind used in DirectBox devices (from 150 to 600 ohms)? cause it's way cheaper to get the transformers from DI Boxes....

thanks again guys for the help  :cheers:
« Last Edit: May 17, 2017, 03:39:09 AM by malow »

Offline Life In Rewind

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Re: Tascam DR-70D - modification discussion
« Reply #129 on: May 17, 2017, 06:38:44 AM »

but, of course, i also need to send the mic's audio "i stole" to the church sound system,


This alone makes your idea - just plain ridiculous...you're really going to inject your gear between the sound console and the PA? - not in my Church!

How about getting a good seat and putting up a pair of microphones and hit record?

No offense to the poster - but Im not sure I'd trust your ability to know what outs the mixer has or doesnt have...or if the soundguy might just be shining you on.
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Offline malow

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Re: Tascam DR-70D - modification discussion
« Reply #130 on: May 17, 2017, 01:58:18 PM »
This alone makes your idea - just plain ridiculous...you're really going to inject your gear between the sound console and the PA? - not in my Church!

How about getting a good seat and putting up a pair of microphones and hit record?

No offense to the poster - but Im not sure I'd trust your ability to know what outs the mixer has or doesnt have...or if the soundguy might just be shining you on.
yes, "injecting" is the only way. every church here have a sound system, but there's no "sound guy" in any church. they install and just turn on/off, and nothing else. some equipment looks like 30 yers old. putting "my system" between is not big deal at all ;)

i already use mic's in the speaker on some churches that does not have sound output. but as the audio system quality is HORRIBLE, looks like audio recorded with a walkie-talkie, plus hum and a lot of noise (something like the audio when Hitler opened the Olympics)

no offense taken. but i believe i'm totally justified in my approach. i will do that, just a matter of "how" i will implement ;)
« Last Edit: May 17, 2017, 06:07:40 PM by malow »

Offline morst

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Re: Tascam DR-70D - modification discussion
« Reply #131 on: May 18, 2017, 04:40:02 PM »
mics >  iso split > two different outputs.

perfect.
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