Topic: Tascam DR-70D 4-channel audio recorder (Part 3)

[groovon]

That has been my impression from the stuff I have read.  I would like to give this a try, but I record a lot of quiet-ish jazz, so if the pres suck it's not worth it to me.

The stock mic preamps definitely don't 'suck', or there would have been very little interest in the deck to begin with.

Dave

[groovon]

Re 'audiophile' op amp swaps/upgrades, this article might be worth a read:

http://nwavguy.blogspot.com.au/2011/08/op-amps-myths-facts.html

Dave

[voltronic]

The stock pres are totally fine at LOW, MID, and the lower half of HIGH.  Once you get into the upper half of HIGH and anything at all in HIGH+ they're pretty noisy (actually extremely noisy at HIGH+).  Most of what I record is classical instrumental and choral, and some of the choral recording is very quiet.  If I recorded louder stuff all the time I probably wouldn't do the mod.  Jim Williams has called the performance of his modded 70D a "poor man's Sound Devices" and I'm hoping for enough reduced noise that I can be one-box for quiet choral recording that needs lots of gain.  Right now, nothing beats my FP24 in that department.  While I don't expect the modded 70D to have the gobs of quiet gain the FP24 has, I would like to be able to go higher gain on 4 channels, at least through the HIGH range.  I also don't expect HIGH+ to improve all that much, as when I asked Jim about it, he said when the gain is that high the input transformer noise will dominate.

[aaronji]

That has been my impression from the stuff I have read.  I would like to give this a try, but I record a lot of quiet-ish jazz, so if the pres suck it's not worth it to me.

The stock mic preamps definitely don't 'suck', or there would have been very little interest in the deck to begin with.

Dave

I never said that they did.  I was asking why the recorder's biggest fan felt the need to mod the pres, and what he perceived the faults to be. 

[voltronic]

Re 'audiophile' op amp swaps/upgrades, this article might be worth a read:

http://nwavguy.blogspot.com.au/2011/08/op-amps-myths-facts.html

Dave

His follow up with measurements is even more interesting.
http://nwavguy.blogspot.com.au/search/label/op%20amps

I think the part of his discussion that's most on point is that you really need to know what you're doing, and don't go swapping parts willy-nilly.  I'm going ahead with this because it's Jim Williams' design, and I know he doesn't do superfluous crap.  He also isn't selling me anything, and I trust him when he says there's an improvement. 

If you read through the article, it does mention that the NJM4580 is an inferior unit, and that's what the 70D uses for the EXT 1/2 input and the output stage.  The NE5532A is the stock opamp for the 70D's XLR inputs.  The JW mod replaces all of those opamps with LME49720MA.

I wonder if his conclusions would be any different if he were examining these in the context of a mic preamp vs. a headphone amp.

[voltronic]

That has been my impression from the stuff I have read.  I would like to give this a try, but I record a lot of quiet-ish jazz, so if the pres suck it's not worth it to me.

The stock mic preamps definitely don't 'suck', or there would have been very little interest in the deck to begin with.

Dave

I never said that they did.  I was asking why the recorder's biggest fan felt the need to mod the pres, and what he perceived the faults to be.

I don't think I'm the #1 fan here, I just happen to own one and maintain the FAQ thread.

My wanting to mod the unit should not dissuade anyone from getting one of these, I don't think.  It's a great unit for the price, and like I said if I didn't primarily record choral music I'd leave it alone.  Who knows?  Maybe the mod will not do anything that I can hear and I'm wasting my money.  But I like to tinker with things, and I'm not going to be able to afford a 788 anytime soon...

[2manyrocks]

http://taperssection.com/index.php?topic=172109.msg2132695#msg2132695

If this recording of Israel Nash is still there, listen and decide if the stock preamps are satisfactory. 

Jim Williams whetted a few folks appetites when he described the 70d as a poor mans SD as mentioned.  If Voltronic can spend $120 and potentially be satisfied recording classical material without forking over $1,900 for a used 744, why not try it? 

As for the comp we were discussing, I would do a baseline recording of something repeatable before and after the mod. 

I will be recording next week on a stage where the HVAC blows down on you and a huge HVAC return is at the back of the stage.  People will be in the audience making noise.  Such is the conditions most of us record in.

  If recording your home piano doesn't do, there's probably a nice piano in the community or local church you could record if you asked nicely.  A nice piano in a nice acoustic space...why not?

[groovon]

That has been my impression from the stuff I have read.  I would like to give this a try, but I record a lot of quiet-ish jazz, so if the pres suck it's not worth it to me.

The stock mic preamps definitely don't 'suck', or there would have been very little interest in the deck to begin with.

Dave

I never said that they did.  I was asking why the recorder's biggest fan felt the need to mod the pres, and what he perceived the faults to be.

I don't think I'm the #1 fan here, I just happen to own one and maintain the FAQ thread.

My wanting to mod the unit should not dissuade anyone from getting one of these, I don't think.  It's a great unit for the price, and like I said if I didn't primarily record choral music I'd leave it alone.  Who knows?  Maybe the mod will not do anything that I can hear and I'm wasting my money.  But I like to tinker with things, and I'm not going to be able to afford a 788 anytime soon...

All fair enough. Any noticeable improvement would be well worth the effort, and esp. at that modest outlay. Hope you're pleased with it 

Dave

[dallman]

Let it run on a source like a piano before and after and lets see if one sounds noticeably better to the masses.

Define "better"....

Perhaps "more accurate" is what we should be looking for.  And unless you were in the room in the first place listening with your own ears then hearing the recordings, then it would be impossible to judge.  At the end of the day, you have to rely on bench tests as subjective comparisons tend to open up cans of worms.  I don't think we're talking major differences here between before and after - the law of diminishing returns will apply (improving something that's already good into something that's even more good in subtle ways).

Better would be the one I like more. You can substitute any word you like, but in a blind listening test either one version will be preferred by a majority or not. 

[leehookem]

http://taperssection.com/index.php?topic=172109.msg2132695#msg2132695

If this recording of Israel Nash is still there, listen and decide if the stock preamps are satisfactory. 

Still on my drive, download away...

[aaronji]

His follow up with measurements is even more interesting.
http://nwavguy.blogspot.com.au/search/label/op%20amps

I think the part of his discussion that's most on point is that you really need to know what you're doing, and don't go swapping parts willy-nilly.  I'm going ahead with this because it's Jim Williams' design, and I know he doesn't do superfluous crap.  He also isn't selling me anything, and I trust him when he says there's an improvement. 

If you read through the article, it does mention that the NJM4580 is an inferior unit, and that's what the 70D uses for the EXT 1/2 input and the output stage.  The NE5532A is the stock opamp for the 70D's XLR inputs.  The JW mod replaces all of those opamps with LME49720MA.

I wonder if his conclusions would be any different if he were examining these in the context of a mic preamp vs. a headphone amp.

I think that NwAvGuy would be disappointed that you want to do the mod after reading his blog!  At least without any measurements...I don't know Williams, but I am kind of sceptical about the "poor man's SD".  If he could actually take a $250 box and make it into an SD clone with less than $100 in parts, you would think he would be selling them.    A lot of them.  My guess is that he either doesn't really believe that himself or he doesn't think he can convince others to believe it.  If the numbers are there, I would like to see them.  By the way, it is kind of misleading to say that NwAvGuy said that NJM4580 is an inferior unit; he actually said, "the 4580 isn’t a bad part but, in my tests, it’s inferior to the NJM4556 in pretty much every way."  So very much a qualified statement.

I also record a lot of quiet music, but, in practically any room with an audience, the ambient noise is higher than my recording chain's.  It is extremely difficult for me to conceive of any setting for live concert recording in which the High+, or even High, would be necessary.  Maybe with dynamic mics or very low output condensers, but otherwise that's a lot of gain...

I don't think I'm the #1 fan here, I just happen to own one and maintain the FAQ thread.

Maybe a little...

http://taperssection.com/index.php?topic=172109.msg2132695#msg2132695

If this recording of Israel Nash is still there, listen and decide if the stock preamps are satisfactory. 

Listening to an isolated recording doesn't tell you much about the pres, I think.  Unless they really suck.

[pohaku]

FWIW, Jim Williams is a well known and well regarded electronics designer who has been in business doing audio gear mods for quite some time, although I think he does less of it now.  If memory serves, I believe he was involved with DBX early on and is responsible for some of their compressor and EQ products.  He also designed and sold a series of mic preamps and did a fairly popular AKG microphone mod.  I think he has enough on his plate that he can pick and choose what he wants to do and probably doesn't see DR70 mods as worth his time and trouble.  He has posted more frequently over on GS.

[aaronji]

Yes, I know who he is by name (and I have a friend that runs some of his mics), but I know nothing about him as a person.  None of which lessens my scepticism of the SD comparison...

[voltronic]

Here's Jim Williams' site - check out the client list: http://www.audioupgrades.com/default.htm

He is the real #1 fan of this thing if you read his posts on GS.  Maybe he's the one to ask why he wanted to mod it.

When he says "poor man's SD" I doubt he means it literally - that the upgraded performance is equal to SD 7-series; just that you're getting closer to that performance for a lower price.  Again, I feel like this mod is a cheap enough risk that I can trust him based on his track record, and again the fact that he's not making money off it.  With someone else that doesn't have that background, I wouldn't necessarily feel the same way.

I'm a bit surprised at the opposition to modding this deck, when many people here have other modded Marantz and Edirol decks from Oade and Busman.  Those guys are doing the same kind of things to those units, and most of those decks are more expensive to start with than the 70D.  Wouldn't you be equally skeptical of those upgrades?

I'm not discounting NwAvGuy's findings, but I'd be curious to hear from one of the builders on the board if everything he found is directly applicable to what we're talking about here.  I'm not knowledgeable enough about electronics to judge that.  Also, remember that the mod in question also includes the addition of 8 poly caps, so it's not just an opamp swap.  Clearly those are important also, or they wouldn't be included.

[aaronji]

I have no opposition in principle to mod'ing a deck (in fact, I own an Oade recorder).  There are some, the PMD660 being the poster child, that unquestionably benefited from an upgrade.  My question is whether this one actually needs it or not.  Would I actually have audibly better results?  Would the numbers look better?  I have no doubt Williams is sincere, but even audio gurus suffer from some pretty profound biases; maybe he thinks it is great solely because he did it.  Who knows.  For sure, I am not headed over to gs to read up on it (I hate the attitudes there), unless he has posted some comps or numbers...

Personally, I would hesitate to void the warranty on a recorder if I wasn't pretty sure it would result in an audible improvement.