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Author Topic: Multiple DAC's ---- ?  (Read 2964 times)

Earwaxxer

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Multiple DAC's ---- ?
« on: February 11, 2014, 07:13:00 pm »
This may seem weird --- Can I run more than one DAC at a time - given they are exactly the same. Can I use more than one DAC at the same time on different USB ports?
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mwillems

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Re: Multiple DAC's ---- ?
« Reply #1 on: February 11, 2014, 07:16:18 pm »
Quote from: Earwaxxer on February 11, 2014, 07:13:00 pm
This may seem weird --- Can I run more than one DAC at a time - given they are exactly the same. Can I use more than one DAC at the same time on different USB ports?

You definitely can. You just need to setup two zones, one for each DAC.  It gets trickier if you need them closely time-synced, but there's absolutely no barrier to using more than one DAC simultaneously. 
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glynor

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Re: Multiple DAC's ---- ?
« Reply #2 on: February 11, 2014, 07:38:42 pm »
Yep.  This is what Zones are for.

MC can even link them and you can play the same thing to both simultaneously.  The sync is usually pretty good, though not good enough for playing in the same room (within clear ear-shot of each other), with most audio devices.  Because USB DACs have their own buffering schemes, however, keeping these in sync can be challenging.

Still though, with most music, for a "whole house audio" setup (each DAC or audio device drives a different room), it works quite well.
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Earwaxxer

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Re: Multiple DAC's ---- ?
« Reply #3 on: February 11, 2014, 07:55:04 pm »
Interesting.. Thanks for the quick reply - what I like to do is use a DAC for the front end and a DAC for the subwoofer, given that the sub is behind the listening position, and a dedicated DAC for the sub sounds fantastic. Do you think the timing issue is a problem - say I was using the exact same DAC for both?
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glynor

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Re: Multiple DAC's ---- ?
« Reply #4 on: February 11, 2014, 08:01:12 pm »
That won't work well.  Others have tried.  There's too much variance, even with the same exact make and model.  Things like the trace lengths on your motherboard to the USB ports, and the lengths of the USB cables probably come into play.  And the DACs give very little control over timing directly.  It's pretty much send the digital audio data down the cable and they'll do what they do.
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Earwaxxer

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Re: Multiple DAC's ---- ?
« Reply #5 on: February 11, 2014, 08:03:53 pm »
Ok cool - another thought - what about going ethernet or wireless to my Transporter with the same signal that is going to my USB DAC?
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Fred1

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Re: Multiple DAC's ---- ?
« Reply #6 on: February 12, 2014, 04:15:34 am »
For your intended use case a multichannel "soundcard" like this would be adequate.
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glynor

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Re: Multiple DAC's ---- ?
« Reply #7 on: February 12, 2014, 07:58:14 am »
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Earwaxxer

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Re: Multiple DAC's ---- ?
« Reply #8 on: February 12, 2014, 08:00:14 am »
Thanks for the replies - its interesting that it can actually be done, I can understand that to sync them exactly would be a huge challenge given all the processing and threads etc.
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Vincent Kars

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Re: Multiple DAC's ---- ?
« Reply #9 on: February 12, 2014, 01:38:44 pm »
It can be done.
The problem with multiple DACs is to keep them in sync.
This can be done if the DACs have a word clock in/out.
One is the master, the other 2 are slaved to the word clock of the master.
A couple of guys run 5.1 this way using JRiver and 3 Mytek DACS.
http://www.quadraphonicquad.com/forums/showthread.php?17298-First-multi-channel-DSD-playback-solution-with-Mytek-and-J-RIver!

Another option is a multi channel DAC e.g. Exasound E28: http://www.exasound.com/
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sirkus

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Re: Multiple DAC's ---- ?
« Reply #10 on: February 12, 2014, 01:55:10 pm »
I use 3 DACs of the same model with a single RME HDSP card (tested with Lynx card, but I don't like the driver) through AES and I have never heard any sync issue.
I did some measures with various waves & noise and I didn't saw any de-sync (at less than 1 ms resolution and during hours) at DACs outputs. I let JRiver manage the upsampling (my DACs upsample to 192).
I believe USB is another story.
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mwillems

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Re: Multiple DAC's ---- ?
« Reply #11 on: February 12, 2014, 02:24:09 pm »
Quote from: sirkus on February 12, 2014, 01:55:10 pm
I use 3 DACs of the same model with a single RME HDSP card (tested with Lynx card, but I don't like the driver) through AES and I have never heard any sync issue.
I did some measures with various waves & noise and I didn't saw any de-sync (at less than 1 ms resolution and during hours) at DACs outputs. I let JRiver manage the upsampling (my DACs upsample to 192).
I believe USB is another story.

Exactly, there's no problem with sync if you have a digital input that carries the clock (like SPDIF or AES), but a USB digital input doesn't carry the clock information.  The thread glynor linked above has some pretty in depth discussion on which DACs will and won't work in multiples.
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Earwaxxer

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Re: Multiple DAC's ---- ?
« Reply #12 on: February 12, 2014, 08:21:14 pm »
Interesting stuff... My Transporter has a 'word clock' input/output. Never really understood what it would be used for. Now I have a better understanding. Much appreciated...
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