Using a P.C. to evaluate a Non-os DAC

[Oli]

This might be useful or worth a try if you do not have access to an oscilloscope-

I happen to own a SBlive soundcard with Live Drive bay at the front for conveniently connecting various audio devices. You might own one too, or be able to connect to S/PDIF out and analogue inputs.

I thought I could use my p.c. to generate a signal, connect my DAC to the S/PDIF output and also connect the DAC analogue input of my soundcard. P.C. oscilloscope software could then be used to watch the resulting trace.

Firstly I found some shareware on the following site:

http://www.sumuller.de/audiotester

(Downloadable trial versions of signal generator, oscilloscope and audio test software are available.)

Using the software I fed a 300Hz -60dB sine wave into the DAC to look for midscale distortion (looks like crossover distortion). I used the tone controls from the Play Control window on the Desktop to filter out excessive high frequencies. I saw no obvious midscale distortion (given the crude apparatus)

I also tried square wave performance (no tone controls this time)
A fairly clean response.

Finally I looked at impulse response. I was impressed that I could see little ringing after each impulse (possibly a little due to the soundcard's input antialias filter), yet when I looked at the SBlive's own output, fed back into the input, more ringing was evident. The pulse response also revealed that my DAC was non-inverting.

Give it a try! It's simply another useful tool.