[linux-audio-user] Multi-channel audio with a computer front end

[Bearcat M. Sandor]

On Monday 15 January 2007 08:54 in an email titled "Re: [linux-audio-user] 
Multi-channel audio with a computer front	end" Paul Davis wrote:
>in other words, i'm totally confused by your goals.
>
>--p
Thanx Paul. Here is what i am trying to do. I want to use my computer as a 
front end in a multi-channel system with a little as possible between it and 
the amplifiers for purities sake. I do not want D/A conversion inside the PC 
as that is noisy and jittery. I do not want to use spdif or toslink as those 
are also jittery (or so i understand).

The Slim Devices (squeezebox or Transporter) are fine for stereo but will not 
work for multichannel due to latency issues. You can send a digital signal to 
a pre/pro from them but that adds a pre/pro in the mix and i'd rather not.

So that leaves me with usb or firewire.

I have seen a few pro audio D/A converters devices that are multi-channel such 
as the Apogee rosetta 800 
(http://www.apogeedigital.com/products/rosetta800.php). The ones that can do 
24/192 (which is also a goal here) are firewire devices.  I have also seen 
some that are USB based but are 24/96 only. That is not as good, but 
acceptable.

Can my system send all the channels to one of these devices via usb or 
firewire and have the device break them out and send them to the appropriate 
speakers. These devices know nothing about DTS, DD and the like so the 
computer would have to determine what sound goes into what channel and send 
all that to the device. I know that were i using a mixing like Audacity or 
Audour it could be done, but the question is can the media player engines 
(gstreamer or xine) do that as well?

If that answer is "no", then i can move the attention down to stereo USB 
devices.  Since linux can use multiple sound cards i could purchase 3 stereo 
USB devices. Could I have Xine or Gstreamer send the front channels to one, 
the centers to another and the l/r rears to another?  If so, am i going to 
run into a problem with timing issues between the 3 devices? Is USB going to 
cause such latency problems?

I could send it all out digitally and just let a pre/pro handle it. However, 
then i am limited to what the pre/pro understands and i want to play with 
things like ambiophonics and such.  I'd also like to do a little mixing and 
recording and a pre/pro isn't meant for that.

I reailse that using usb/firewire in this way will result in my using digital 
attenuation instead of analog. This is not ideal, but could be solved with 
passive volume controls on the other end. However, since i am looking at 
24-bit and my listening levels are quite low it should not introduce any 
limits in the audio resolution.

If i need to explain further i am happy too.

Thank you.