Topic: Syncing a V3 Word Clock output with a DMIC-20 AES REF input

[Chuck]

Has anyone done this?
Connected the V3 WC output to the DMIC-20 AES REF input?
Of course my goal is to have the two units share the same clock, so I can sync up the two stereo recordings later in post production.

I would appreciate hearing from anyone who has tryed to do this. Does it work well? Are the recordings synced up perfectly?


One problem for me, is that my V3 is opti-moded, but I assume there is another mod to add the WC output back?

Added: 02-26-2007

Yes, it is possible to sync the sample rates! Read my post on page 5 of this thread

[gratefulphish]

Has anyone done this?
Connected the V3 WC output to the DMIC-20 AES REF input?
Of course my goal is to have the two units share the same clock, so I can sync up the two stereo recordings later in post production.


I would appreciate hearing from anyone who has tryed to do this. Does it work well? Are the recordings synced up perfectly?

I don't believe that the DMIC AES input has anything to do with the word clocks syncing.

One problem for me, is that my V3 is opti-moded, but I assume there is another mod to add the WC output back?

You might be better off trying to swap your opti-mod for an unmodded one, if you found that you can do what you are trying to accomplish.

[Chuck]

I don't believe that the DMIC AES input has anything to do with the word clocks syncing.

Hmmm... I don't know whet else it could be for
I know it's possible to use an external clock with the DMIC-20. So, that has to be where it gets the signal from.

[trajhip2000]

it looks to me like the AES Ref input isn't a wordclock input per se, but rather it will sync to the wordclock it extracts from a "full" AES input signal. so I would guess you could use one of the AES outputs on the V3 to sync the clocks, altho it looks like you will need some sort of adapter/cable to go from XLR to BNC. I'm thinking maybe they do it this way so you can sync to sources that don't have a formal WC out.

Steve

[OFOTD]

One problem for me, is that my V3 is opti-moded, but I assume there is another mod to add the WC output back?

The opti-mod replaces the hardware for the word clock.  While I am not sure if they can redo the WC I do know that you can have one or the other but not both.

For the expense of having that done to your V3 the method for creating a matrix in WaveLab seems to be more time effective, IMO.

[twatts (pants are so over-rated...)]

From the DMIC24 manual:

http://www.gpsys.com/SP_User_Guides/DMIC-24-UG.pdf

[Chuck]

Cool. I just talked to Neal at Grace and he said basically the same thing. I don't need the word clock out. He said the AES out should work. I also have an e-mail into Graham Patten to see what they say.

As far as trying to match up two digital sources in WaveLab, that's not for me, it is WAY to slow and tedious. I'll report back when I get the DMIC to tell whether it works.

[Chuck]

Thanks Terry. I found a real cheap DMIC-20, so i want to try this. If both units run under the same clock, the files should sync up perfectly... right?

[twatts (pants are so over-rated...)]

Thanks Terry. I found a real cheap DMIC-20, so i want to try this. If both units run under the same clock, the files should sync up perfectly... right?

I'm not sure, I've never had any experience with wordclock.

ToddR made mentioned of using wordclock in the thread talking to Bean about his next upgrade:
http://taperssection.com/index.php/topic,79473.msg1058390.html#msg1058390

He refers to running the WC out of the V3 into a 722 so the 4 channels sync like an R4. 

So yeah, I think your files should sync... 

Terry

[gratefulphish]

I took a look at the DMIC-24 manual, and it seems to indicate that the input is to ensure that the DMIC samples at the same rate as the other device.  From the manual:

Connecting AES Reference
The DMIC-24 can be synchronized to an alternate output frequency (from the default frequency)
by connecting a valid AES reference signal to the AES REF BNC connector. The EXT REF LED
on the front panel lights when a valid reference signal is applied.
To phase lock the unit’s sample frequency to a reference, connect a reference signal (between 30
KHz and 50 KHz sampling rate) to the AES REF BNC connector. The AES signal output will now
phase-lock to the incoming reference — independent of the DMIC’s default reference frequency.

It does not seem to be a wordclock in/out.

[Chuck]

I took a look at the DMIC-24 manual, and it seems to indicate that the input is to ensure that the DMIC samples at the same rate as the other device.  From the manual:

Connecting AES Reference
The DMIC-24 can be synchronized to an alternate output frequency (from the default frequency)
by connecting a valid AES reference signal to the AES REF BNC connector. The EXT REF LED
on the front panel lights when a valid reference signal is applied.
To phase lock the unit’s sample frequency to a reference, connect a reference signal (between 30
KHz and 50 KHz sampling rate) to the AES REF BNC connector. The AES signal output will now
phase-lock to the incoming reference — independent of the DMIC’s default reference frequency.

It does not seem to be a wordclock in/out.

That's funny, I read that a whole different way. It sounds to me like by runing AES out of the V3 to the AES in on the DMIC-20 they will share the same clock. That's what I want.

[ethan]

One problem for me, is that my V3 is opti-moded, but I assume there is another mod to add the WC output back?

I would just find someone who has a non-modded V3 who'd trade with you.

-e

[Todd R]

Chuck -- you should talk to Scott on the CO Crew.  He got a Mytek Stereo192 A/D with a word-in and got his V3 reverse modded back to the original (not the first to have it done according to Grace).  He's been using the Mytek and V3 with word out to record 4channels and mix them in post.  With all 4 channels using the same clock, syncing is a breeze.

FWIW, I'm reading the Dmic-20 the same as you -- AES Ref will strip the incoming AES input to get the clocking info and will use that as the clocking reference.  Pretty cool.

[Chuck]

If I lose the optical out on my V3, I'll have to quit using the iRiver until I can figure out how to add a coax in on it...
I love the iRiver!

When I talked to Neal at Grace, he said it should work from the SPDIF out on the V3. The GP literature says it needs to be AES out, but the BNC input is not balanced, so that presents another problem.

I wish I had the DMIC now, so I could try it!  

[Chuck]

Chuck -- you should talk to Scott on the CO Crew.  He got a Mytek Stereo192 A/D with a word-in and got his V3 reverse modded back to the original (not the first to have it done according to Grace).  He's been using the Mytek and V3 with word out to record 4channels and mix them in post.  With all 4 channels using the same clock, syncing is a breeze.

FWIW, I'm reading the Dmic-20 the same as you -- AES Ref will strip the incoming AES input to get the clocking info and will use that as the clocking reference.  Pretty cool.

Thanks for the great discussion guys. I'll let you know whether it works or not when I get the DMIC-20.

Gee, this will be great if it really works. I was planing to buy or build an analog mixer to mix two stereo sources on the fly, but this will be MUCH better if it works! 

[Brian Skalinder]

Chuck -- you should talk to Scott on the CO Crew.  He got a Mytek Stereo192 A/D with a word-in and got his V3 reverse modded back to the original (not the first to have it done according to Grace).  He's been using the Mytek and V3 with word out to record 4channels and mix them in post.  With all 4 channels using the same clock, syncing is a breeze.

Hey Scott - you out there?  Just curious as I dream about future 4-ch options...

What recorders are you using behind the V3 / Mytek?
What pre in front of the Mytek?
Mics?

[gratefulphish]

I took a look at the DMIC-24 manual, and it seems to indicate that the input is to ensure that the DMIC samples at the same rate as the other device.  From the manual:

Connecting AES Reference
The DMIC-24 can be synchronized to an alternate output frequency (from the default frequency)
by connecting a valid AES reference signal to the AES REF BNC connector. The EXT REF LED
on the front panel lights when a valid reference signal is applied.
To phase lock the unit’s sample frequency to a reference, connect a reference signal (between 30
KHz and 50 KHz sampling rate) to the AES REF BNC connector. The AES signal output will now
phase-lock to the incoming reference — independent of the DMIC’s default reference frequency.

It does not seem to be a wordclock in/out.

That's funny, I read that a whole different way. It sounds to me like by runing AES out of the V3 to the AES in on the DMIC-20 they will share the same clock. That's what I want.

It refers repeatedly to the sample frequency, which must be between 30-50KHz (like 32, 44.1 or 48), and then seems to indicate that this will automatically cause the DMIC to sample at the same frequency.  My R-4 Pro has an indicator, so that if I have a different sample rate set on my V3, than on the R-4 Pro, it lets me know, so that I can reset one or the other.  This connector just seems to do the job for you, preventing two different devices from sampling at different rates.  I might e-mail GP for an answer.  I would like to know myself.  This is just my interpretation of the manual, and we all know how well those are all written.

[Todd R]

Brian -- it might be worth dropping Scottsch3 a line in the CO crew thread, I don't know how much he trolls the rest of ts.com.

He uses at least a MT for one of his recorders, but I seem to remember he has some sort of multi-track recorder.  The mytek side is V2>mytek, plus he has the V3.  He also archives for Brothers Past, so I think he often is getting the channels from FOH or the monitor board.  But for mics he has DPA 402x, DPA subcards, and DPA 4061's (notice a trend?).

On the AES Ref issue, I don't think it'd be easy to implement what Gratefulphish is saying -- you'd need to somehow have the ability for the DMic to generate any sampling frequency between 30khz and 50khz, which would be no easy feat.  It seems much more likely to simply strip this clocking frequency information off the AES input.  Of course, checking with GP is a good idea, but I don't think the DMic would be using the AES signal to simply decide what to clock at -- it'd then still need to somehow generate that clock.

[gratefulphish]

Maybe this helps clear things up.  From the front of the DMIC manual:

Two versions of the DMIC-24 are available:

• 44.1 KHz Model
This model defaults to 44.1 KHz, via the internal crystal. However, if an external
reference is applied to the AES REF connector, the output frequency will lock to the
reference.

• 48 KHz Model
This model defaults to 48 KHz, via the internal crystal. However, if an external reference
is applied to the AES REF connector, the output frequency will lock to the reference.

NOTE The printed legend on the rear panel indicates the default frequency.

This is the "default" frequency referred to in the other section that I quoted.  In other words the frequency is fixed, depending on the model you purchase, unless you go in through the AES reference input, in which case, it will lock to that frequency, overriding the default.  Note that it appears that you can only get 32, 44.1 or 48 under any circumstances. 

[Chuck]

Brian -- it might be worth dropping Scottsch3 a line in the CO crew thread, I don't know how much he trolls the rest of ts.com.

He uses at least a MT for one of his recorders, but I seem to remember he has some sort of multi-track recorder.  The mytek side is V2>mytek, plus he has the V3.  He also archives for Brothers Past, so I think he often is getting the channels from FOH or the monitor board.  But for mics he has DPA 402x, DPA subcards, and DPA 4061's (notice a trend?).

On the AES Ref issue, I don't think it'd be easy to implement what Gratefulphish is saying -- you'd need to somehow have the ability for the DMic to generate any sampling frequency between 30khz and 50khz, which would be no easy feat.  It seems much more likely to simply strip this clocking frequency information off the AES input.  Of course, checking with GP is a good idea, but I don't think the DMic would be using the AES signal to simply decide what to clock at -- it'd then still need to somehow generate that clock.

I called GP, and the guy I need to talk to is out for the rest of the day.
I e-mailed him and will call if I don't hear something by late tomorrow.

Todd, when you say Scott had his opti-mod V3 reversed, that sounds weird, because when I talked to Neal over at Grace, he said the sync should work fine from either the SPDIF (RCA) or AES (XLR) outputs. Essentially making the extra work to re-add the clock output un-neccessary.

I have been working on trying to figure out how to get coax SPIDIF input rigged into my iRiver iHP-120 just in case I really do need the clock out jack on the V3 back to make this work...    

Of course, if this is all possible, I have a few INA217's around here and will probably want to gain pot mod the DMIC too.

I am mod crazy!  

[Todd R]

Grateful -- I'm not sure where you're getting that the Dmic will only do 32k, 44.1k, and 48k -- it seems quite clear from the manual that is will lock to any external source between 30k and 50k.  Chuck's got the call in, that should clear up exactly how it works.

Chuck -- I mentioned Scott simply since he has been doing 4ch mixes using two rigs with common clocks, thought you might be interested in how he does the post production mixes.  He needed the reverse mod done since the Mytek only takes a word clock in.  It isn't set up for stripping the clocking info off an AES stream like we're assuming the DMic does.  So you wouldn't need this reverse mod done.  (I'm just imagining that a work clock input needs just a word clock stream.  Is Neal at Grace saying any word clock in can just take an AES full stream automatically and strip off the audio to get the clocking info?  In which case, I don't know why you'd need a separate word clock out if you already have two AES outputs on the V3.)

[Chuck]

Grateful -- I'm not sure where you're getting that the Dmic will only do 32k, 44.1k, and 48k -- it seems quite clear from the manual that is will lock to any external source between 30k and 50k.  Chuck's got the call in, that should clear up exactly how it works.

Chuck -- I mentioned Scott simply since he has been doing 4ch mixes using two rigs with common clocks, thought you might be interested in how he does the post production mixes.  He needed the reverse mod done since the Mytek only takes a word clock in.  It isn't set up for stripping the clocking info off an AES stream like we're assuming the DMic does.  So you wouldn't need this reverse mod done.  (I'm just imagining that a work clock input needs just a word clock stream.  Is Neal at Grace saying any word clock in can just take an AES full stream automatically and strip off the audio to get the clocking info?  In which case, I don't know why you'd need a separate word clock out if you already have two AES outputs on the V3.)

That's what I understood Neal saying... at least for my needs. Maybe I won't have to undo the optical mod on my V3. That would be great!
If this works I'll be four track recording... on the cheap, soon. I recently made a deal to purchase another iRiver, the iHP-140. 

It's a wonder this question hasn't come up before, since both these pieces of gear have been around for a while.

[trajhip2000]

I don't believe a typical wordclock input will take a regular digital feed and pull the wordclock out - but I do believe that the DMIC-20 AES input will do that based on their specs. Lots of devices are set up to sync their wordclock to that extracted from a digital feed, I'm pretty sure my 744T does that.

Steve

[Todd R]

So, another iRiver, huh?  Looks like you're putting your days of DAT behind you.  Are you planning on modding the Dmic-20 for an optical out?  I've heard it's pretty easy, at least electronically -- getting a hole cut into the back of the Dmic might be the hardest part.  Get in touch with Richard/poorlyconditioned, I think it was him who did the optical mod.

[gratefulphish]

Grateful -- I'm not sure where you're getting that the Dmic will only do 32k, 44.1k, and 48k -- it seems quite clear from the manual that is will lock to any external source between 30k and 50k.  Chuck's got the call in, that should clear up exactly how it works.

What other frequencies have ever been used between 30 and 50K other than 32, 44.1 and 48?  It does say anything between those numbers, but my guess is that it was easier than saying, "between 32 and 48K"  Just sounds nicer to say 30-50, even if it doesn't mean anything.  As I also read the manual, it would also mean that you could not do 24/88.2, 96 or 192 under any circumstances.

Another issue is that the DMIC-20 is a 20 bit converter, and a V3 is either 16 or 24, creating other compatibility, synching and conversion issues.

[Todd R]

Ok Chuck, we're going to need a report back from those GP folks.    I'm still assuming they mean anywhere between 30k and 50k.  I'm not sure how often it came into play, but for some reason video people use 44,056 not 44.1k for sampling, just as a for instance.

You should be able to mix a 4ch mix of the V3 at either 16 bits or 24 bits with the 20bit recording from the Dmic -- that shouldn't cause a problem with syncing.  It does make me wonder on how to record off the DMic though -- it seems like truncating the 20bit signal to 16 bits would be bad.  Maybe there's enough/the right level of noise in the system to provide some natural dither to 16bits.

And I'm with you Chuck -- why haven't we thought of this before.  Seems like a nice way of doing 4ch mixes.  I may need to look into a used DMic.

[Chuck]

Grateful -- I'm not sure where you're getting that the Dmic will only do 32k, 44.1k, and 48k -- it seems quite clear from the manual that is will lock to any external source between 30k and 50k.  Chuck's got the call in, that should clear up exactly how it works.

What other frequencies have ever been used between 30 and 50K other than 32, 44.1 and 48?  It does say anything between those numbers, but my guess is that it was easier than saying, "between 32 and 48K"  Just sounds nicer to say 30-50, even if it doesn't mean anything.  As I also read the manual, it would also mean that you could not do 24/88.2, 96 or 192 under any circumstances.

Another issue is that the DMIC-20 is a 20 bit converter, and a V3 is either 16 or 24, creating other compatibility, synching and conversion issues.

Good points. I'll see what Graham Patten says tomorrow. I am hopeful, at least for now.

So, another iRiver, huh?  Looks like you're putting your days of DAT behind you.  Are you planning on modding the Dmic-20 for an optical out?  I've heard it's pretty easy, at least electronically -- getting a hole cut into the back of the Dmic might be the hardest part.  Get in touch with Richard/poorlyconditioned, I think it was him who did the optical mod.

I may do an optical mod on it, if all this stuff shakes out correctly. There is a thread around here somewhere. I think you are right, that Richard did mod one of his units. He's been having problems with his DMIC-20's lately I heard.

Todd, didn't you swap the instrumentation chips out of Josh's old DMIC-20 a while back? INA217's? I happen to have some I was going to use in a pre-amp project. If all this works right, I will do the gain potentiometer mod that allows adjustment between the various 5 db steps. The gain will be set just like the V3 in that respect...  I hope it's cool to run line-in on the DMIC at it lowest gain setting.

[Todd R]

Todd, didn't you swap the instrumentation chips out of Josh's old DMIC-20 a while back? INA217's?

Could be, I really don't remember at this point.  We talked about doing it, I just can't remember if we followed thru since Josh was having troubles with his DMic.  I'm pretty sure others have done it.  And the INA217 (or THAT1510) are drop-in replacements for the SSM2017 chip, which is dip-socket mounted into the DMic, so swapping them is a breeze.

[Chuck]

My e-mail to Graham Patten:

I do field recording and need to be able to sync two stereo sources to the same clock for four channel, digital, recording.
I have a Grace Lunatec V3, which has SPDIF (RCA) and AES (XLR) outputs. I also have a DMIC-20 available, but I don't have it in my hands yet.

What I need to know is... Can I run the Lunatec V3 SPDIF or AES output into the AES input (on the back of the DMIC-20) to sync the DMIC-20 to the V3?

My V3 does not have a word clock output, so that is not an option for me.

The goal is to have the digital recordings made from both devices, in perfect sync, so that they can be edited together without the clock drift they would have if they were recorded on two separate machines with two separate clocks. Is this possible and if so, am I thinking about it the correct way?

Any help or advice would be greatly appreciated.

Thanks,

Chuck Miller



This in from GP:

Hello Chuck,
 
You will have no problem using the DMIC-20 AES input with S/PDIF for Reference.
 
Mike 
 
Mike Sauter
Test/Service Technician
(888) 622-4747
www.gpsys.com


I am in business!  I will report back when I get the DMIC-20 to confirm...

[gratefulphish]

I am really not sure what that reply meant, even though your question was written clearly.  First of all, as I indicated yesterday, this just does not seem to be what their manual says.  Second, in his answer he seems to suggest that you can just plug a SPDIF source into the AES input, and that would just "work."   As I have understood it, and I have spent some time reading about it, (as all of my DAT decks were SPDIF, but the R-4 Pro is AES) the signals are different, at different Ohms, and to truly convert data from one to the other can be accomplished with a cable that will harshly perform the function, or boxes costing hundreds or even thousands of dollars to properly do the signal conversion. Finally, he just said for "reference."  Reference in their manual seemed to only be sampling frequency. I have seen nothing in there about word clock.  Is this guy the senior tech?   Hasn't anyone else ever experimented with this function.  It still doesn't sound right to me, but give it a try (I would try to borrow the DMIC first, and find someone with an unmodded V3) and you can find out for sure.

[Chuck]

I sent out another e-mail, to Mike at Graham Patten, asking for clarification.

Gee, I wish I had the thing here, so I could just try it, to see if it works...

[Jamos]

Just read through every post in this thread...

From the GP literature, it does appear that Gratefulphish is right, in that they say the DMIC will strip the audio out of an AES (or SP/DIF) signal and just lock onto the sampling frequency.  It doesn't say anything specifically about the clock.

Since both the folks at Grace and the GP tech say using the SP/DIF will be fine, I'd guess that when the DMIC locks onto the incoming signal it also locks onto the clock.  Since it needs to stay locked, it must use the host's clock to keep receiving to frequency info.

Seem right to anyone else?

[Chuck]

This is what I sent in my last e-mail:

Mike:
 
Thank you, again, for the quick response.
I have been talking this over with some colleagues and we need some clarification.
Will connecting the S/PDIF output from the Lunatec V3 to the AES input on the DMIC-20 lock the DMIC-20 to the V3 clock?
We want the digital output to the recorders from both devices to be in perfect sync, with no clock drift, so the resulting audio files can be edited together later.
Some are saying that they think sending the S/PDIF out to the DMIC-20 will just set the DMIC-20 to the same sample rate and bit rate, not lock the clocks together.
 
Thanks again for your assistance,
Chuck

I will post the response when I get it.

[trajhip2000]

I was about to reply that locking onto the sampling frequency is the same as locking onto the clock, but I guess it's possible that it could do the former and not the latter. However, it would seem a little silly to do the former and not the latter, since you could just select the sampling freq anyways - I guess it would make sense if you wanted to use some weird sampling freq that is not one of the std presets, but that must be so infrequent that I don't see why you'd design a piece of gear like this to do that. So I still believe that it will sync to the V3 signal, but I guess that should be counted as opinion and not fact at this point

[Todd R]

Maybe this is why Gratefulphish and I do not seem to be on the same page.  It's been awhile since I reviewed the spdif and AES standard, but it's my understanding that the sampling rate and the clock are essentially one in the same.  The sample rate is twice the clock rate, but the exact clocking information can be very easily generated from the sampling frequency.  By locking to the sampling frequency of the AES reference (the V3), the DMic will be inherently locked to its clock.

[Todd R]

Oops, beaten to the punch. 

[Chuck]

So, will my e-mail question get the answer I need?

[gratefulphish]

I was about to reply that locking onto the sampling frequency is the same as locking onto the clock, but I guess it's possible that it could do the former and not the latter. However, it would seem a little silly to do the former and not the latter, since you could just select the sampling freq anyways - I guess it would make sense if you wanted to use some weird sampling freq that is not one of the std presets, but that must be so infrequent that I don't see why you'd design a piece of gear like this to do that. So I still believe that it will sync to the V3 signal, but I guess that should be counted as opinion and not fact at this point

First, as I read it, the DMIC-20, is only twenty bit, no matter what the incoming signal is.  Nothing is going to make it 16 or 24 bit.  Second, the sample rate on the DMICs are fixed.  You can buy a 44.1 or a 48 KHz DMIC-24, but they are otherwise not selectable, except apparantly, by using the AES input, which seems to only lock the sample rate, at between 30-50 KHz.  As far as I can tell, this is like DAT decks synching up, and automatically adjusting the the sample rate of the lead deck.  If wordclock was in all signals, and were as easy to send and synch, then why don't we see it on anything but the most high-end gear?  And from what I have seen, the wordclock in/outputs are dedicated solely to the clock function, and the audio signal is sent through another cable.  Let's wait to see the response to the second e-mail, which appears to clarify what is being asked.  Actually, the first e-mail had the question right, I just think that GP's response was a non-answer.

[Todd R]

So, will my e-mail question get the answer I need?

Yes, it should.  Plus soon enough you can just test it.  This part of your question might confuse GP a bit (or at least it does me):

Some are saying that they think sending the S/PDIF out to the DMIC-20 will just set the DMIC-20 to the same sample rate and bit rate, not lock the clocks together.

Are you differentiating between sample rate and bit rate, they seem like they'd be the same thing.  Or are you talking about bit depth?  The bit depth and sample rate/clocking info have nothing to do with one another.

Each data "word" in the SPDIF and AES standard are defined as to what data is in what bit place.  As part of this, there are bits in the word set aside for the 24-bit audio info or the 16-bit audio info.  This is exclusive of the clock timing.  So the AES ref input on the DMic is only going to give you clocking timing (though how it works is yet to be determined), it will have nothing to do with bit depth.  (Though maybe that's not what you're getting at with bit rate.)

[Todd R]

First, as I read it, the DMIC-20, is only twenty bit, no matter what the incoming signal is.  Nothing is going to make it 16 or 24 bit.  Second, the sample rate on the DMICs are fixed.  You can buy a 44.1 or a 48 KHz DMIC-24, but they are otherwise not selectable, except apparantly, by using the AES input, which seems to only lock the sample rate, at between 30-50 KHz.  As far as I can tell, this is like DAT decks synching up, and automatically adjusting the the sample rate of the lead deck.  If wordclock was in all signals, and were as easy to send and synch, then why don't we see it on anything but the most high-end gear?  And from what I have seen, the wordclock in/outputs are dedicated solely to the clock function, and the audio signal is sent through another cable.  Let's wait to see the response to the second e-mail, which appears to clarify what is being asked.  Actually, the first e-mail had the question right, I just think that GP's response was a non-answer.

Yep, agreed about not being able to make the DMic have a bit depth other than 20 bits.  But as I mentioned above, bit depth has really nothing to do with syncing up two sources and using a common clock.  You can sync up two sources perfectly and still be syncing up 44,100 words per second (x2 sources) and still be syncing up nothing but garbage.  That is, there are some inherent problems with recording a 20bit stream with a 16bit recorder (that will truncate the extra bits), but that won't affect the ability to sync up the two sources.  It's just that one source will have truncation errors in it, and those truncation errors (some report hearing strident highs and a fatiguing sound with truncated sources) will be carried into the merged 4ch mix.

As to the other, I don't think that the AES ref input is anything like 2 DAT decks syncing up on sampling frequency.  In that latter case, both decks are using their own internal clocks to clock the 44,100 samples per second.  The DMic AES ref input from their description seems to create the clock timing from the AES/spdif data stream.

[gratefulphish]

Todd, I hear what you are saying, and quite frankly the bit depth issue alone would make me think about doing this at all, even if the clocks could by synched.  But I went back and read the manual sections that I quoted in some of the prior posts, and everything refers to synching frequencies (as opposed to the fixed frequency of the DMIC) and there is not one single word about clock speed (pun sort of intended).  Only Graham Patten knows for sure, hopefully.  Let's wait and see how they respond.

[Chuck]

So, will my e-mail question get the answer I need?

Yes, it should.  Plus soon enough you can just test it.  This part of your question might confuse GP a bit (or at least it does me):

Some are saying that they think sending the S/PDIF out to the DMIC-20 will just set the DMIC-20 to the same sample rate and bit rate, not lock the clocks together.

Are you differentiating between sample rate and bit rate, they seem like they'd be the same thing.  Or are you talking about bit depth?  The bit depth and sample rate/clocking info have nothing to do with one another.

Each data "word" in the SPDIF and AES standard are defined as to what data is in what bit place.  As part of this, there are bits in the word set aside for the 24-bit audio info or the 16-bit audio info.  This is exclusive of the clock timing.  So the AES ref input on the DMic is only going to give you clocking timing (though how it works is yet to be determined), it will have nothing to do with bit depth.  (Though maybe that's not what you're getting at with bit rate.)

Yeah, that last sentence, on my e-mail, was an unfortunate after thought...
When most folks use the DMIC-20 the last 4 bits are truncated when recording to 16 bit, and no one complained about it then. Do you guys really think this will be an issue? I'm hoping the DMIC sends out essentially the same signal that the V3 does when they "sync" up.

[trajhip2000]

The differences in word length won't matter operationally, if the input word length is above what the input receiver can handle then the extra bits will be truncated. Whether they matter or not sonically is open to debate I guess. Truncation isn't ideal, but usually for live recordings the noise floor is high enough that I wouldn't consider it a big issue. Altho the DMIC-20 is spec'd at 20 bit, iirc the actual resolution is something below that due to the noise floor (you could check this on the spec sheet, just divide the dynamic range by 6 to get the resolution in bits (i.e. true 16 bit has 96 dB, 20 bit 120 dB, etc). I was told by G-P when I talked to them years ago that the noise floor in the DMC-20 is high enough that it acts as kind of a pseudo-dither and that you're getting something pretty close to 16 bits of resolution on the output, so in this case I think the possible sonic penalty is relatively minor.

Steve

[Todd R]

Yep, Steve's got it right there.  There is some debate about the sonic impact of truncating, esp from 24 bits to 16 bits.  But the noise level in the venue might make that moot.  And I've seen stuff from both Denecke re: the AD20 and RME Audio re one of their former A/Ds saying the same thing that Steve said the G-P guys told them.

Remember, essentially all dither is doing is adding noise to the LSB of the dithered word (eg, the 16th) so that it is random when the lost 4 or 8 bits are stripped off.  If the inherent noise of the A/D is such that that 16th LSB is already random, then an actual dither function would not be needed.  I guess the same should hold true if the noise of the audio being recorded in the venue makes that LSB random, the same should hold true, though I've never really thought of it that way.

[trajhip2000]

Cranesong actually sells something they call an analog dither cd: http://www.cranesong.com/analogdither.html Presumably somewhat more sophisticated than crowd noise, but the same general idea I think. As long as the "dither" noise isn't correlated with the audio you're recording (another way of saying you want the LSB to be random) it will function in much the same way.

Steve

[Chuck]

This from Graham Patten today:

Charles,
 
The clock will be derived from the Ext sync, S/PDIF, input.  Only with no ext.
reference does the DMIC run on the internal 48KHz crystal.  The clock will be
locked to the ext. ref.
 
Where ever you send the output of the DMIC will need to be locked to the same
clock if you want everything sync'd to the same clock.
 
Mike

[Todd R]

Cool, looks like it'll work then.  Looking forward to hearing how your experiments go.

BTW, that last line looks like he is just saying you need to be recording off the DMic with a bit perfect recorder -- obviously can't use a recorder that re-samples in the digital input (like the R4?).

[gratefulphish]

This from Graham Patten today:

Charles,
 
The clock will be derived from the Ext sync, S/PDIF, input.  Only with no ext.
reference does the DMIC run on the internal 48KHz crystal.  The clock will be
locked to the ext. ref.
 
Where ever you send the output of the DMIC will need to be locked to the same
clock if you want everything sync'd to the same clock.
 
Mike

Apparently, I stand corrected, but I am still having trouble understanding why just about no other devices on the market offer this type of simplified wordclock synching.  The last sentence is also unclear.  Does that just mean a bit perfect deck, or a deck that also has a wordclock input?  While the R-4 resamples, the R-4 Pro does not.  In other words, having the V3 synched to the DMIC may be one thing, but having the decks to which the signals are going may be another.  That seems to be why they have these very expensive, multi-channel word clock generators.  Anyone?

[Chuck]

It's going to be a while until I'll be able to properly test all this out. I don't have the DMIC yet and I will have to add an optical output to it before I can record to the iRiver. I do have another iRiver on the way though. I figure I may as well replace the BNC connectors on the DMIC with RCA's as they are much easier to come by and work with.

Who'd have guessed I'd be a gear slut. My wife is going to kill me, and tonight being Valentines Day night and I'm going out to record Particle.    She did take that news well, I think.

[gratefulphish]

It's going to be a while until I'll be able to properly test all this out. I don't have the DMIC yet and I will have to add an optical output to it before I can record to the iRiver. I do have another iRiver on the way though. I figure I may as well replace the BNC connectors on the DMIC with RCA's as they are much easier to come by and work with.

Who'd have guessed I'd be a gear slut. My wife is going to kill me, and tonight being Valentines Day night and I'm going out to record Particle.    She did take that news well, I think.

You won't need to worry about the synching, if you are buried 6' under.  Go get some flowers.  Your testicles depend on it.

[Chuck]

It's going to be a while until I'll be able to properly test all this out. I don't have the DMIC yet and I will have to add an optical output to it before I can record to the iRiver. I do have another iRiver on the way though. I figure I may as well replace the BNC connectors on the DMIC with RCA's as they are much easier to come by and work with.

Who'd have guessed I'd be a gear slut. My wife is going to kill me, and tonight being Valentines Day night and I'm going out to record Particle.    She did take that news well, I think.

You won't need to worry about the synching, if you are buried 6' under.  Go get some flowers.  Your testicles depend on it.

Yeah, it's not as bad as all that, but thanks for the advice. 

[gratefulphish]

See my avatar.  Next to the switch for "Man" it just says "On/Off", the rest is self-explanatory.  Flowers go a long way, chocolate usually doesn't hurt either.

[Chuck]

I had not taken the time to check out that avatar. Yup you've got it right. 

[trajhip2000]

I wonder why resampling of two synced inputs would be a problem - if they are synced when they come in and then both are resampled by a recorder with its own clock, then they should end up synced at the recorder, no?

Stev

[Todd R]

Apparently, I stand corrected, but I am still having trouble understanding why just about no other devices on the market offer this type of simplified wordclock synching.  The last sentence is also unclear.  Does that just mean a bit perfect deck, or a deck that also has a wordclock input?  While the R-4 resamples, the R-4 Pro does not.  In other words, having the V3 synched to the DMIC may be one thing, but having the decks to which the signals are going may be another.  That seems to be why they have these very expensive, multi-channel word clock generators.  Anyone?

I'm pretty positive the last sentence just means you must make sure you're recorder doesn't screw up the syncing that the DMic will provide.  Which means that you must have a bit perfect recorder that does not re-sample on it's digital input.  Re-sampling on the digital input simply means it will use its internal clock, rather than the clock of the DMic (which has been locked to the clock from the AES ref).  They're not saying you'd need a wordclock in on your recorder, if that were the case, it wouldn't matter what clock the DMic was using.

As to why not more companies do it, who knows?  It takes some R&D to do, takes some circuitry to accomplish, and requires another connector on the outside of the box.  I guess most companies don't think it is worth it.

[Todd R]

I wonder why resampling of two synced inputs would be a problem - if they are synced when they come in and then both are resampled by a recorder with its own clock, then they should end up synced at the recorder, no?

Stev

You've lost me here, Steve.  Unless you use the same clock to resample the synced inputs, they will no longer be in sync.  What do you mean by synced when they come in and both resampled by a recorder?

[trajhip2000]

Sorry, I hadn't looked back at the beginning of the thread in a while, and was thinking that Chuck was talking about running into the R4, which does resample inputs (instead I see the R4 was mentioned by gratefulphish) - but since the R4 does that using the same clock on all 4 channels it shouldn't matter and they should still be in sync after resampling (I believe). But certainly if you are running into two diferent recorders and one or both of them resample and they aren't linked by wordclock then the two recordings will not be synced. But that does make me wonder - if you feed two digital sources that aren't synced into something like an R4 that does resample, then I guess they would end up synced?

Steve

[gratefulphish]

Sorry, I hadn't looked back at the beginning of the thread in a while, and was thinking that Chuck was talking about running into the R4, which does resample inputs (instead I see the R4 was mentioned by gratefulphish) - but since the R4 does that using the same clock on all 4 channels it shouldn't matter and they should still be in sync after resampling (I believe). But certainly if you are running into two diferent recorders and one or both of them resample and they aren't linked by wordclock then the two recordings will not be synced. But that does make me wonder - if you feed two digital sources that aren't synced into something like an R4 that does resample, then I guess they would end up synced?

Steve

Yes, I through the R-4 reference in.  But the R-4 only accepts two channels of digital input, same with the R-4 Pro.  The R-4 resamples, the R-4 Pro does not.  Since only two channels are digital on each machine, this discussion is somewhat academic as to them.  Chuck began this thread discussing using the DMIC and the V3 into different decks.  That is where the whole sync issue came up.  That is why I raised the issue of whether the decks themselves had to be synched by wordclock, and not just the pre/ADs.

[trajhip2000]

gotcha. Does the R4 Pro sync its internal clock to the incoming digital stream? if not, it would seem to me the R4 Pro has a significant disadvantage, since w/o resampling I don't see how the digital and analog sources will be in sync.

Steve

[Todd R]

Yeah, that sure is an interesting upshot to the R4 re-sampling.  Since it re-samples the digital input off its internal clock, you're right -- you should be able to feed it a digital signal, say from a V3, and then have 2 analog channels input, and then all 4 channels would be in sync.  Unless the R4 Pro has some way of accepting a wordclock in (don't have any idea if it does), then you wouldn't be able to sync an incoming digital signal with the analog channels.

[gratefulphish]

As it was explained to me by Edirol's techs, as long as all four channels are being recorded on the same deck, they are going to be in sync.  I don't believe that the resampling, or not, has any effect on that, since the four channels are being recorded on four tracks, on the same machine, at the same time. I could be wrong, but that is what I was told.

[trajhip2000]

funny, I was kinda wondering about that - since the files all start and stop at the same time you'd think that would be true. however,  I just remembered a thread on the Sound Devices board where I was asking about feeding two channels digitally from a V3 to a 744T and also using the WC from the V3 to sync the 744T (I even bought a WC cable). The SD support guy said that even though the clocks would be digitally in sync, there is a difference in something called the "group delay" (iirc) between the A/D chips in the V3 and SD that would mean they won't be exactly time-aligned - so even tho the files would start and stop at the same time and their clocks would be synced, the data streams wouldn't hit the recorder at the same time. my recollection is that we're talking about a very small difference, I believe he gave us a formula based on sampling rate, I never did any calculations - but I think we're talking about low msec at most. I guess this principle would apply to most of the previous discussion on this thread. certainly the most important thing to have is the clocks synced, that way you only have to worry about aligning the whole files as opposed to individual songs (potentially) if the clocks are mis-matched.

Steve

[Todd R]

As it was explained to me by Edirol's techs, as long as all four channels are being recorded on the same deck, they are going to be in sync.  I don't believe that the resampling, or not, has any effect on that, since the four channels are being recorded on four tracks, on the same machine, at the same time. I could be wrong, but that is what I was told.

Was he just talking in general, or was he referring specifically to the R4 or specifically to the R4 Pro?  This ^ makes sense when talking about the R4, but doesn't seem right about the R4 Pro.  If you feed 2 digital channels into the R4 along with 2 analog channels, the R4 will resample the digital channels using the same clock as is being used on the analog channels -- so all should be in sync (though not perfectly time aligned).  But in the case of the R4 Pro, the digital channels are not being resampled and will be sampled off the clock chip of the V3, not the clock of the R4 Pro, which will be sampling the analog inputs.  Bottom line, in the case of the R4 Pro, the digital channels are being clocked by one wordclock, and the analog channels are being clocked by another.  So it doesn't seem to me that in this case the digital channels and analog channels will be in sync.

[TNJazz]

Bottom line, in the case of the R4 Pro, the digital channels are being clocked by one wordclock, and the analog channels are being clocked by another.

I don't believe this is possible - you can only have one master clock in a digital system.

From what I've been reading it seems that word clock is being confused with sampling rate.  Word clock does not carry audio, it merely emits a signal based on the sampling frequency.  It's a speed reference (sync) that tells the recording device how fast to run.  Resampling the bits on digital input doesn't really apply - they are still running off the same clock so they will be at the same speed - they have just been resampled but their speed has not changed.

So if a device is set to receive word clock input (external) the analog channels should run at the same clock speed as the signal coming in.  Whether they are time aligned or not is another matter entirely, but they will be in sync.

[Todd R]

Bottom line, in the case of the R4 Pro, the digital channels are being clocked by one wordclock, and the analog channels are being clocked by another.

I don't believe this is possible - you can only have one master clock in a digital system.

From what I've been reading it seems that word clock is being confused with sampling rate.  Word clock does not carry audio, it merely emits a signal based on the sampling frequency.  It's a speed reference (sync) that tells the recording device how fast to run.  Resampling the bits on digital input doesn't really apply - they are still running off the same clock so they will be at the same speed - they have just been resampled but their speed has not changed.

So if a device is set to receive word clock input (external) the analog channels should run at the same clock speed as the signal coming in.  Whether they are time aligned or not is another matter entirely, but they will be in sync.

You might be right, but that is not my understanding of things.  I'm not sure you're following me, but I'm not confusing wordclock with sampling rate -- the wordclock is what the system is using to generate its timing in the internal circuitry -- it is an actual clock: rising clock edge makes things happen with the circuitry, falling clock edge is ignored, 1/44,100 of a second later and there is another rising clock edge and the logic chips react accordingly.  Your sample rate can be at 44.1k, but you still need to have a system clock to make that happen.  Gear will have that clock onboard, and depending on design, can take the wordclock of an external system, which is a lot of what we were discussing.

From the initial discussion, the Dmic can take a wordclock reference from an external source and will use this for clocking information.  In this way, the DMic will have exactly the same clock timing as the reference gear (say a V3).  This is akin to your final sentence -- getting an external reference wordclock will insure that all channels are being recorded from the same clock. (I'm sure you know it, but 44.1k is not 44.1k, is not 44.1k.  Each sampling of 44.1k will be dependent on the particular system clock that generates that sampling rate.  Even though two different digital streams have a nominal sampling of 44.1k, they both will be ever so slightly different unless the sample rate was clocked from the exact same reference clock.)

The issue about the R4 is different though than the DMic, since the DMic accepts an external wordclock reference and the R4 does not.  So this might be where my confusion comes in, but this is my understanding:  Digital recorders taking a digital signal can either accept that digital signal exactly (including the inherent timing information embedded in that signal) -- this is the bit perfect digital recording we're talking about, or the recorder can re-sample that digital stream, which makes the recorder not bit perfect.  When the recorder does this, it resamples the digital stream based on its own internal clock, so the now resampled digital stream no longer has the exact timing of the original digital stream -- it is now timed by the internal system clock of the recorder.

So this gets back to the issue with the R4 vs the R4 Pro. The R4 will resample the incoming digital stream using its own internal clock, the same clock that is used to generate the timing of the A/D conversion on the analog inputs -- thus all 4 channels have now been clocked by the same clock.  In the case of the R4, it does not resample the incoming digital stream.  So this stream has been clocked by the V3 that fed the digital stream.  The analog inputs though will have been clocked by the system clock of the R4, so they will not be completely synced to the digital input, which was clocked by the V3.

Reading this over, I think this might be part of the confusion:

Word clock does not carry audio, it merely emits a signal based on the sampling frequency.  It's a speed reference (sync) that tells the recording device how fast to run.

The wordclock is not just a reference to tell the recording device how fast to run.  It is an actual digital clock (think of a squared off sine wave) that is required in almost all digital systems using ICs.  The clock doesn't provide a just a speed reference telling something how fast to run, it actually provides the exact timing of running the system.  So it isn't a syncing mechanism, or at least I find that language pretty confusing.

[TNJazz]

OK, maybe I'm not understanding this completely.

Here is what MOTU says about word clock:

"Word clock is a time base reference only, providing a measurement of the passage of time and the speed at which samples should go by."

They are referring to time and speed, but resampling of the digital input should have no effect on either of these variables to my way of thinking.  It simply changes 1's to 0's and vice versa.

I'm trying to understand why there is a need to sync two devices to a single clock when the third device supposedly utilizes its own clock anyway (the R4, according to all the statements above)?  Would clocking the V3 and the DMIC not be useless in that case?

I'll go back into lurk mode for a while now...

[trajhip2000]

resampling is really not much  different than what happens in your original A/D conversion, so it has to be tied to a clock. when you resample that's controlled by the clock in the resampling device, so you lose the incoming clock and the timing basis is now the new clock - unless the resampling device can take it's clock from the input stream, which the Edirol may or may not do, I don't know.

this is giving me a headache...

Steve

[Todd R]

I'm trying to understand why there is a need to sync two devices to a single clock when the third device supposedly utilizes its own clock anyway (the R4, according to all the statements above)?  Would clocking the V3 and the DMIC not be useless in that case?

There is no need.  There are two different discussions going on in this thread.  One is how Chuck can use the V3>recorder to record two channels, and then record 2 more channels of mics>DMic20>second recorder, with the DMic externally referenced to his V3.  This will enable him to easily make 4ch mixes.  The R4 discussion has nothing to do with any of this.

The other is a discussion about how the R4 and R4 Pro handles clock timing, particularly in regards to recording 2channels digitally and 2ch analog.

On the other point, Steve has got it -- when we say a digital input resamples, it has to resample based on some clock.  What happens is that it will be resampling based on its internal clock, which will be different from the external clock of the original A/D that created the digital feed.

So all of this is a total aside from Chuck's original thread, but may be very important to users of the R4 Pro.  That is, it sure looks like they're going to be totally screwed if they want to do a 4ch mixdown to 2channels if they use 2 digital channels on input and two additional analog channels.

[TNJazz]

There are two different discussions going on in this thread.

 

That's why I couldn't figure out what was going on.  I'll go back and re-read it with that in mind.

[Chuck]

I'm trying to understand why there is a need to sync two devices to a single clock when the third device supposedly utilizes its own clock anyway (the R4, according to all the statements above)?  Would clocking the V3 and the DMIC not be useless in that case?

There is no need.  There are two different discussions going on in this thread.  One is how Chuck can use the V3>recorder to record two channels, and then record 2 more channels of mics>DMic20>second recorder, with the DMic externally referenced to his V3.  This will enable him to easily make 4ch mixes.  The R4 discussion has nothing to do with any of this.

The other is a discussion about how the R4 and R4 Pro handles clock timing, particularly in regards to recording 2channels digitally and 2ch analog.

On the other point, Steve has got it -- when we say a digital input resamples, it has to resample based on some clock.  What happens is that it will be resampling based on its internal clock, which will be different from the external clock of the original A/D that created the digital feed.

So all of this is a total aside from Chuck's original thread, but may be very important to users of the R4 Pro.  That is, it sure looks like they're going to be totally screwed if they want to do a 4ch mixdown to 2channels if they use 2 digital channels on input and two additional analog channels.

I'm really enjoying this discussion. I'm learning and re-learning things I've only, really, had a general grasp of. This stuff is important to know, especially when working with several digital devices. Thanks guys.

[Chuck]

Good news!

I got the DMIC-20 this week and did some modifications to it. Some to improve performance, some are meant to make it more usable in the field, at least from my perspective.

- Replaced the phantom power supply switch (back panel) with a lower profile switch
- Added low profile, power switch (front panel) above power LED
- Removed the BNC connector (front panel) and replaced with gold RCA jack
- Removed the AES Ref BNC connector (back panel) and replaced with gold RCA jack
- Removed the AES XLR output (back panel) and replaced with Toslink (optical) output*
- Added (2) 5k ohm log taper pots for variable gain between 5 db steps (front panel)
- Replaced the (2) SSM2017 original instrumentation op-amps with (2) INA217

* this made it possible to make a recording from the DMIC-20 into an iHP-140 optical input
My V3 already has the optical output modification.

Today, I got to test it. 

This is what I did...

- While I was doing the modifications to the DMIC-20, I tested it along the way, to ensure that it was functioning properly. So I tested the box after I was done and was happy to find it worked properly.
- I ran a 75 ohm coax cable (RCA to RCA) from the V3 SDPIF output to the DMIC-20 AES Ref input (Thus "syncing" the V3 sample rate reference to the DMIC-20)
- I set the V3 to 44.1 kHz, 16 bit
- I connected a CD player analog output into the DMIC-20 XLR inputs (with attenuator cable)
- I recorded, with 2 microphones ~ one foot away from my monitor speakers, the same audio into the V3, XLR inputs
- I played several compact discs and recorded for ~4 hours (the iRiver's automatically split the files at 2 GB) into an iHP-120 (V3) and iHP-140 (DMIC-20) using the optical inputs
- I then imported both stereo files into CuBase. I aligned the beginnings of the audio files visually (and sonically)
- I then looked at the end of the files and they still lined up perfectly (in phase too!) There must be a phase reversal in either my playback system or one of the pre-amps? I listened to the beginning and end of the files, muting and unmuting each stereo recording listening for delay or any other anomolies. I heard none. 

I can conclude, from my test, that running the SPDIF output into the AES Ref input on the DMIC-20 does make it possible to make two recordings (through the analog inputs on both pre-amps) at the exact same sample rate, thru the two pre-amps to two separate recorders. The files matched up visually and sonicaly after 4 hours record time.

This is very good news, for me. Now, I have a four channel recording system, on the cheap.


BTW, I really want to thank Richard (poorlyconditioned) for his generous sharing of information on doing the optical modification to the DMIC-20. With his help I was able to do that mod in less than an hour with less than $3 in parts!

[rowjimmy]

+t
Did you take any pics?

[Chuck]

I'm not done yet, but I can take some pictures...

[rowjimmy]

Just curious how everything looks. I wondered how/where you would fit the toslink connector in there but, seeing that you removed the AES-XLR output, there's probably lots of room.

If only one could toss those dip switches...

[Chuck]

Here are some photos I took this morning. I originally had the optical output mounted on a Neutrik DBA cover plate, but I botched the cut out on it and have reverted to a piece of scrap aluminum I had until i can order another Neutrik cover.

[Chuck]

Just curious how everything looks. I wondered how/where you would fit the toslink connector in there but, seeing that you removed the AES-XLR output, there's probably lots of room.

If only one could toss those dip switches...

As far as the DIP switches go, it is possible to completely eliminate them, but I am setting mine up to operate like a V3. The resistor network sets up the basic gain in 5 db steps (stock DMIC-20). Then I experimented with different values for the potentiometers and found that a 10k audio taper pot provides appox. 8.5 db for "fine" adjustment. I found the 5k pots (Todd Romero mod) to provide a little less than 5db of adjustment. I haven't tried 15 k pots yet, but that may just be ideal, putting the fine adjustment in the 10 db or more range.

If anyone is thinking about doing the gain pot mod, I have one more suggestion. I bought 5 of the Panasonic 10k audio taper pots and found only two that matched well enough for my use. Next time I will by more, so I have more to choose from for proper matching.

Also, the unit I bought had a busted phantom power section, so you may see some of my modifications to the circuit to fix that problem.

Chuck

[rowjimmy]

Looking good.
Although I'm sure the neutrik plate will be slick, It looks pretty clean as-is.
Nice work.
+t

I I know todd and have used a todd-mod dmic. I didn't have enough time with it to feel comfortable but my impression of the dip switches + pots was not the greatest.

Twas a good, clean sound, though.

[gratefulphish]

Reviving Part 2 of this thread, dealing with the issue of the R-4 Pro, using digital input via AES/EBU and also using analog input on the other two channels.

I finally got around to speaking to Edirol tech support about this issue, as I was concerned about the suggestions that using a V3 for the digital input would be governed by the V3 wordclock, while the analog inputs would be governed by the R-4 Pro's internal wordclock.  Tech support had to contact R&D in Japan for the answer and get back to me.  Apparantly, in the same way that the DMIC gets its wordclock from the V3, when you select digial+analog on the R-4 Pro, it then uses the wordclock of the incoming digital signal to control both the digital input, and the analog inputs, i.e. it's all run by the same clock, in this case the V3, so there will be perfect synching and no potential for drift.  Hope this answers any questions.

[Chuck]

I have made two recordings so far using the SPDIF out on the V3 connected to the AES REF input on the DMIC-20 and I am quite happy to report that the audio is in sync on the recordings made from both units. This is especially good, as I was working on an analog summing mixer to mix the two sources in the field (on the fly) because I didn't have the $$ for an all-in-one four track digital recorder. This is a much better solution. Now I can record with four channels or two channels as needed. Thanks for the great discussion. I learned a lot trying this for myself and reading what you all have said in your postings.

Chuck