XO-1.5 audio input DC mode

C. Scott Ananian cscott at laptop.org
Wed Nov 17 14:49:47 EST 2010

On Wed, Nov 17, 2010 at 2:46 PM, C. Scott Ananian <cscott at laptop.org> wrote:
> As a wild stab at a first guess, it sounds like a software problem to
> me -- seems like xoscope is not successfully turning off either the
> bias voltage or the decoupling capacitor (high pass filter).  Perhaps
> a silent failure of some sort?

If you've got access to a signal generator (or another machine with a
sound card), feeding in a 1kHz square wave with an offset (say 0 off,
1V on) is probably a better diagnostic than using your potentiometer.
If my wild guess is correct, then you should see a characteristically
rounded square wave with no offset.  Then you could poke at the
software until (a) the rounding goes away, and (b) you see the offset
you expect, which would indicate that the decoupling capacitor has
successfully been switched out of the circuit.

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