using sound card as 8-channel waveform generator

using sound card as 8-channel waveform generator

Post by mike-bardi » Thu, 21 Dec 2006 05:47:09

I have a system with an ASRock 939Dual-VSTA motherboard which has an 8
channel I/O sound capability (CM 6501 like). I want to use this to
create an arbitrary set of waveforms that I can feed into an external
piece of equipment to test it that it is working correctly. The
waveforms are sinusoid based at frequencies up to maybe 10KHz.
Sampling at 44KHz would be fine. The idea is to create a multi-channel
audio file of the waveforms and play this back through the PC sound
card. Initially I can probably use something like Audacity to create
the audio file. I have also experimented with using Matlab/Simulink
simulation package to create multi-channel audio files.

When I play the files back I seem to get the waveforms merged together
on some of the sound card outputs - checking them with a scope. I
don't seem to see 8 separate channels with different waveforms.

Being a newbie to sound card technology I am not even sure what I am
trying to do is possible. Maybe I need some special form of audio file
or Windows driver or a particular type of sound card.

Any hints or tips on how to achieve desired result (assuming it is
possible) would be appreciated.


using sound card as 8-channel waveform generator

Post by NoSpa » Thu, 21 Dec 2006 23:14:00

I'm also not sure this is possible. I couldn't find any specs on the
CM6501except that it was supposed to be 7.1 channels. I'm a
little wary of this "surround sound" stuff, especially the 0.1 channel
part. Could it be that the chipset produces all these outputs by
synthesizing them from normal stereo or something? That was the
norm for many years in home entertainment systems.

However, if the card really is capable of more than 2 discrete
channels, you will need to make sure your WAV file uses the
proper format, which is WAVEFORMATEXTENSIBLE.
I don't have all the details on that at hand, so you'll have to
Google for it. If you are sure that's what you've got (such
as by peeking at the header of the file), then I'd suspect the
sound chipset.

Best regards,

Bob Masta

Data AcQuisition And Real-Time Analysis
Home of DaqGen, the FREEWARE signal generator


using sound card as 8-channel waveform generator

Post by mike-bardi » Fri, 22 Dec 2006 23:31:27


Thanks for the information; I will have a look into the WAV file