Is the audio frequency response of your PC reliable and correct?

[StanleyB]

I have been using CD test discs for years to test the frequency response of items such as CD players, DACs, etc. And in general the outcome was quite good. I found a site recently at http://www.audiocheck.net where I downloaded some of their test files and burnt them onto a CD to add them to my collection of test tones etc. I checked them out with my CD player connected to a DAC and then a scope. All looked well. No problems there.
But then recently I decided to check out the audio stream on one of my laptops through a DAC and the results viewed on as cope. I also played the same sounds from the CD via my CD player.
The results were startling. The PC audio response in the 20Hz to 20kHz range was not uniform at all! My PC is weaker in the high frequency range.
I am going to do some more tests, but wondered if anyone has ever done any sort of tests on the audio output frequency response of their PC.

[Reffc]

I have been using CD test discs for years to test the frequency response of items such as CD players, DACs, etc. And in general the outcome was quite good. I found a site recently at http://www.audiocheck.net where I downloaded some of their test files and burnt them onto a CD to add them to my collection of test tones etc. I checked them out with my CD player connected to a DAC and then a scope. All looked well. No problems there.
But then recently I decided to check out the audio stream on one of my laptops through a DAC and the results viewed on as cope. I also played the same sounds from the CD via my CD player.
The results were startling. The PC audio response in the 20Hz to 20kHz range was not uniform at all! My PC is weaker in the high frequency range.
I am going to do some more tests, but wondered if anyone has ever done any sort of tests on the audio output frequency response of their PC.

I suspect it's not so much the PC as the sound card used. It's important (when testing loudspeakers for example) that signal generator software used on PC's is played back through a sound card which offers some guarantee of accuracy in the audible band...not all do as you've found out! If this matters, a decent sound card to do the job can be had for well under £100 these days. There may be other contributing factors such as noise and has introduced into the output. The way I tested mine involved using a calibrated mic and signal generators compared with an accurate purpose sold CD test disk and evaluate pink noise response. The two should match exactly at a given SPL.

[StanleyB]

The problem with that view is that the digital output (via USB or SPDIF) should not be affected by sound card issues. I tried the same tests on three different brands of DACs, 5 laptops, two USB converters, and on TOSLINK and coax. In each case the high end was lower than the low end.

[Stratmangler]

Which media players have you used, and how are they set up in respect of the external devices that are connected to?

[StanleyB]

I have used all sorts of configurations and media players just in case that could have been the issue.
I'll make a spreadsheet and go through the various options again.