On 7/7/22 8:55 AM, Bob kb8tq via time-nuts wrote:
Hi
Yes, you do need to know the system gain. Since we are talking about
gain at audio, measuring the gain directly is not a crazy thing to do. One
of the things that makes audio spectrum analyzers a nice tool for this that
they eliminate the “variable gain to the sound card” issue.
Some sound card setups are a lot easier to work with than others. If you
are restricted to the sound input on your motherboard things can get a bit
crazy. It is not unusual for folks to dig up a “pro” (whatever that means
on a sound card ) card that has better drivers and more access to this and
that.
Given how fast the PC world changes, the board that was a wonderful thing
last time somebody dove in, likely is long out of production by now. The drivers
that made it work so well may have been “improved” and it no longer gives
you the control it once did. This makes for a bit of trial and error to get it
all
going.
Bob
Rather than a sound card, it might be better to pick a small singleboard
like a Teensy that has a decent ADC, and make a "sampling engine" with a
USB interface.
Or, in general, going to a USB interface sound interface might be good.
You can get them with a lot of channels (at least 8) and they sample
simultaneously, so the uncertainty in USB latency won't bite you.
Google for things like the Focusrite Scarlett
I've not tried it for this kind of application, but it is likely to have
better noise properties than a "inside the PC" card. Typically 24 bit
converters and 192kHz sample rates.
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