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

Bearcat M. Sandor HomeTheater at feline-soul.com
Mon Jan 15 22:07:56 EST 2007


I'm replying to both of you Paul and Mark in one email. It's just easier that 
way and clearer.  Thank you for both of your responses. Now, on to my 
clarifications and questions.  I apologise for the confused questions, but 
i'm well confused. My aim is to use my computer as the front-end and and have 
it do all of the DSP  for maximum flexibility. I want as few components as 
possible between the computer and amps, unless i *have* to use a pre-amp for 
extra gain. More clarifications are below.

>On 1/15/07, Paul Davis <paul at linuxaudiosystems.com> wrote:
><SNIP>
>
>> first of all, D/A conversion associated with the computer does need to
>> be noisy - there are many devices with external breakout boxes now - and
>> it does not need to be jittery if you are willing to spend money on good
>> equipment. i would agree that doing it inside the chassis case is
>> probably not the best arrangement, but thats not much of an issue these
>> days.
>
><SNIP>
>
>I agree with everythign PAul said although I *think* he meant to say
>"D/A conversion associated with the computer does (NOT) need to be
>noisy". D/A converters inside of a computer are a bad idea but mounted
>externally in a breakout box they are no different than the same
>converters sitting inside a recording studio.
>
>
><SNIP>
>
>> RME solutions have too high a channel count for you, however.
Actually, i used to have an RME Hammerfall 9636 it worked very nicely, except 
that there are no mixers in it. In fact it was Paul that helped me with the 
Alsa config files to keep it going. Thanks Paul! In the years since i've 
forgotten all about it. It might be just what i need. Currently, i am using  
nvidia on-board sound and i can hear the fans of the PC in my speakers along 
with a little buzzing. Horrid :)   Granted this is with my ear near the cone, 
but any noise adds coloration. I'm looking at purchasing a pair of Gallo 
Reference 3.1 and a set or Red Dragon Class D monoblocks all of which are 
which are *very* revealing and this noise must go.

><Revisiting your original post>
>
>Will a linux
>movie player using xine or gstreamer be able to send the correct channels of
>the Dolby Digital/DTS to the individual channels on a multi-channel pro
>device?
>
></Revisiting>
>
>I run an RME HDSP 9652. I suspect that's similar to what Paul is
>running these days. I have used xine with hdspmixer to mix 5.1 output
>into other formats, like stereo. There is no reason you couldn't do
>the same mixing 5.1 into 4.1 or some other arrangement that works with
>your specialized setup. It worked great for me. xine outputs six
>channels of audio. You can do whatever you want wither each channel -
>ladspa plugins, combinations routed how you like, etc. It's quite easy
>with hdspmixer.

>As others have said I would stay away from the FreeBob solutions at
>this time, unless you have a stomach for working through whatever
>issues you are going to come across. You could do a *Very* nice
>high-end home theater system using an HDSP 9636 and a good set of
>D/A's. You might look at one of the low-cost (<$250) 8 channel ones
>for all the extra channels and use something like a Benchmark DAC1
>which has really great sound, albeit a bit pricey but not totally over
>the top, for left and right.

I'm a little confused as to what connection i would use with the hdsp 3696 and 
the Benchmark DAC1 to get 24/192 in at least 4 channels.

Yes, thank you.  I'm looking for 4 channels actually as i don't like center 
channels (left, right, rear right, rear left).  8 channels is fine actually 
as i can use the other channels for something. I may use it as as DAW 
sometimes or multi-zoning,

Hsdpmixer sounds just like what i have been looking for, but i looked around 
for details on it and could find nothing. Is this an app to interface with 
the internal mixer of the card or is it the name for the mixer on the card 
itself?

I've read in the audiophile press that usb/firewire is more desirable then 
spdif because usb/firewire has lower levels of jitter. Of course if the 
difference is truly inaudible i don't care.

The less components and cables between the computer and the amps the better 
(generally unless you need extra gain provided by a pre-amp). If i were to 
use an RME Hammerfall DSP 9632 and go straight into an amplifier (monoblocks) 
I would still get all the computer noise as i would be doing D/A inside the 
box, right? Of course i could get a fanless video card, power supply and 
chipset, but then the case fans might still add noise, not to mention the 
electronics itself.  Of course this won't work if the gain on the RME is not 
high enough (i'd be using the balanced outs).  However, i assume i'll get the 
Buzz of Doom if my computer powers down and the amps are on.

So if need to send it out to a breakout box. Would this be better done through 
adat or spdif? I'm looking for at least 4 channels of 24/192 being delivered 
to 4 monoblocks and i thought that neither could do that.  If i got 2 
Benchmark DAC1s they would not necessarily be in synch right?

I've always liked the RME cards and i just read somewhere that Paul is 
actually a RME dealer. I'd be looking to buy a card sometime this summer. 
I'll contact you then.

>Hope this helps,
>Mark



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