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Audio Equipment Testing

Brian

By Brian
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sandall Technical Manager

sandall

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I thought I would try this with my UA-101. The resulting sound files are here: https://soundcloud.c...-1/source-sweep

 

(go to More > Download file on each track to download the uncompressed 192kHz AIFF files, the streaming is resampled down).

The summary is that (provided that your software stack is transparent) this interface goes most (but not quite all) the way to 80kHz when set to 192kHz sample rate. There are some artefacts visible in the highest frequency range.

 

I also borrowed a Focusrite Scarlett 2i4 interface. This is 24bit / 96kHz interface. Under Windows with MME I had to switch Audacity project rate down to 96kHz to get playback. So using the same sweep to 80kHz, the last section will be lost because the Nyquist frequency is 48kHz. However the recording cut out at just below 23kHz (not very cleanly).

I then opened the Windows Sound control panel and changed the Properties > Advanced > Default Format from 44100Hz to 96000Hz on both recording and playback. Then re-do the test. On the second pass, the bandwidth has now increased to more than 40kHz.

So the take-away message is that (depending I'm sure on your software), if your interface sample rate is software selected, you need to change the default rate in Windows Sound control panel as well as the rate in your software

Thanks Richard. When I played your files they cut out at around 23kHz, but when downloaded & imported into Audition both the 96k & 192k were fine (though I obviously couldn't see anything above 48kHz). I had previously tried pink / white noise & tones from Audition & Audacity with everything set at 96k (I should have read your bit about the Windows panel more carefully!) with hoped-for results. All I need now is a cheap'n cheerful way of getting analogue at up to 48kHz into the laptop (I'm sure the analogue Line-in will be bandwidth-limited).

 

Thanks Steff. Back in the day most amplifier testing & design was done with square-waves & a 'scope, though I don't remember all the maths.

 

Sorry Brian, I seem to have hijacked your thread.

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