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HD I/O vs 192 Digital Section only Monitor Controllers
Old 11th May 2011
  #1
Here for the gear
 

HD I/O vs 192 Digital Section only

Dear Slutz,

This is my virgin thread...
I ve been searching thoroughly without finding much info on my issue.
Hope some slutz will have the answer.

Straight to my concern :

I just got new HD I/O on top of my old 192s
For monitoring I m using the Grace m906 (in 5.1 configuration) with AES Ins (they have Analog ins as well)

My Question is:
Is there any sonic difference between the old 192 and the new HD I/O on the Digital side (AES/ADAT/Toslink).
Before I start to patch things up I m torn between still using my old 192 or swithcing to the new HD I/O to feed my Grace monitoring ??
Will there be any improvement at all? I read many times the AD/DA section got some noticeable improvement but I read nowhere about the digital section...
Thanks again, and hope someone has the answer or maybe did some tests on this matter.
Old 11th May 2011
  #2
Lives for gear
 

I can't imagine there's anything different about it. Bitz is Bitz, and as long as your D/A chain is the same, it should sound the same.
Old 11th May 2011
  #3
Go forth and do not worry, nor speculate further.
Old 12th May 2011
  #4
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It's possible that there could be a subtle difference between the clocking of the old and new interfaces. The best way is to test it both ways.
Old 12th May 2011
  #5
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Quote:
Originally Posted by nst7 View Post
It's possible that there could be a subtle difference between the clocking of the old and new interfaces. The best way is to test it both ways.
Thanks for actually pointing that out.
I was also thinking more about the interfacing between the new HD I/O and other digital unit not in term of bits
(I agree they are the same bits everywhere)
but clocking might be a factor that got improved from the old 192s.

Anybody who did a test in this area specifically?
HD I/O + Digital monitoring controller VS 192 + the same controllers?
Old 18th May 2011
  #6
Quote:
Originally Posted by CYL View Post
Thanks for actually pointing that out.
I was also thinking more about the interfacing between the new HD I/O and other digital unit not in term of bits
(I agree they are the same bits everywhere)
but clocking might be a factor that got improved from the old 192s.

Anybody who did a test in this area specifically?
HD I/O + Digital monitoring controller VS 192 + the same controllers?
I just did a 72 hour marathon session with two HD I/O's. I asked the owner of the studio to remove the external clock from the path. These converters are very much higher definition compared to the 192. They also have lower noise and higher dynamic range, by a lot.

Not sure I can answer your question about the bit's....I will place money that the AES/EBU stream from a 192, is the same AES/EBU stream from HD I/O. AES/EBU protocol has not changed in between these two interfaces, so there should be no reason to think there will be a problem. Does your AES/EBU re-clock the AES/EBU inputs?
Old 18th July 2011
  #7
Gear Maniac
 

Quote:
Originally Posted by Roc Mixwell View Post
I just did a 72 hour marathon session with two HD I/O's. I asked the owner of the studio to remove the external clock from the path. These converters are very much higher definition compared to the 192. They also have lower noise and higher dynamic range, by a lot.

Not sure I can answer your question about the bit's....I will place money that the AES/EBU stream from a 192, is the same AES/EBU stream from HD I/O. AES/EBU protocol has not changed in between these two interfaces, so there should be no reason to think there will be a problem. Does your AES/EBU re-clock the AES/EBU inputs?
Bits is bits. If you're using the asynchronous sample rate conversion inputs, and they changed this between the 192 and HD I/O, then perhaps there would be a difference. But, beyond that, and in the absence of extreme error conditions, you're just shuffling binary data around.
Old 19th July 2011
  #8
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Zep Dude's Avatar
 

Actually, the 192 is what applies the clocking to the bits, so there are aspects that could impact the jitter, thus quality of the AES signal. Improvements in the power supply or architecture of the digital card could positively impact the signal.
Old 19th July 2011
  #9
Gear Maniac
 

Quote:
Originally Posted by Zep Dude View Post
Actually, the 192 is what applies the clocking to the bits, so there are aspects that could impact the jitter, thus quality of the AES signal. Improvements in the power supply or architecture of the digital card could positively impact the signal.
This is misinformation. The 192 only "applies clocking to the bits" when it's operating as an A/D converter, or an asynchronous SRC. (True, if the device connected to the Avid AES input is another A/D converter, then it must be resolved to the same clock. But as has been pointed out before, its own clock recovery circuit is as important here as the clock to which it is resolving. If you're using the AES I/O as an insert - eg. an effects loop - then you are just shuffling bits around.)

Last edited by lukehatpadl; 19th July 2011 at 09:43 AM.. Reason: Clarify
Old 21st July 2011
  #10
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Zep Dude's Avatar
 

Quote:
Originally Posted by lukehatpadl View Post
This is misinformation. The 192 only "applies clocking to the bits" when it's operating as an A/D converter, or an asynchronous SRC. (True, if the device connected to the Avid AES input is another A/D converter, then it must be resolved to the same clock. But as has been pointed out before, its own clock recovery circuit is as important here as the clock to which it is resolving. If you're using the AES I/O as an insert - eg. an effects loop - then you are just shuffling bits around.)
From what I understand, AES to AES signal (as in just a digital loop) has to carry clock. The receiving unit in the loop still needs to receive clock to stay in sync. Only signals within the TDM bus (pro tools mixer, plugin operation etc) are just shuffling bits.

From the Lavry Engineering Website:

"The AES/EBU format is self-clocking: word clock is embedded in the digital audio stream. As a result, a single cable carries two channels of audio plus word clock. "
Old 21st July 2011
  #11
Gear Maniac
 

Quote:
Originally Posted by Zep Dude View Post
From what I understand, AES to AES signal (as in just a digital loop) has to carry clock. The receiving unit in the loop still needs to receive clock to stay in sync. Only signals within the TDM bus (pro tools mixer, plugin operation etc) are just shuffling bits.

From the Lavry Engineering Website:

"The AES/EBU format is self-clocking: word clock is embedded in the digital audio stream. As a result, a single cable carries two channels of audio plus word clock. "
True, I suppose you can't assert that an all-digital device could not be sensitive to jitter. However, generally I don't believe this to be the case, see Bob Katz's article at http://www.digido.com/jitter.html:

Quote:
Jitter and DSP-based Processors
Most DSP-based software acts as a "state machine." In other words, the output result on a sample by sample basis is entirely predictable based on a table of values of the incoming samples. The regularity (or irregularity) of the incoming clock has no effect on the output data.

Exceptions to "state-based" DSP processes include Asynchronous Sample Rate Converters, which are able to follow variations in incoming sample rate, and produce a new outgoing sample rate. Such devices are not "state-machines", and jitter on the input may affect the value of the data on the output. I can imagine other DSP processes that use "time" as a variable, but these are so rare that most normal DSP processes (gain changing, equalization, limiting, compression, etcetera) can be considered entirely to be state machines.

Therefore, as far as the integrity of the data is concerned, I have no problems using a chain of jittery (or non-jittery) digital devices to process digital audio, as long as the digital device has a high integrity of DSP coding (passes the "audio transparency" test).
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