[sdiy] computer soundcard mic question

[Jay Schwichtenberg]

Deknow,

Sounds like a bad connection or cable. Could be an open wire in the cable or
the jack wasn't plugged in all the way. Some computer mics are electret
which require a voltage and that is usally on the jack's ring.

Jay

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Dean Stiglitz
> Sent: Wednesday, May 29, 2002 3:39 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] computer soundcard mic question
>
>
> hi all,
>
> we had a client in the other day (my day job is
> selling/installing/training speech recognition software), who was
> having a very strange problem.
>
> as soon as a mic was plugged into the laptop (either into the
> analog mic in, or via a usb audio converter), a bad hum would
> start up (audiable via the speakers, and trashing any chance to
> get speech recognition to work)...it is not uncomon to have
> problems with the built in sound on a laptop, but the usb pod
> almost always clears it up.
>
> my theory was that there was some kind of grounding problem, and
> the mic cable was acting as an antenna.  today i came in planning
> to lift the ground, and save the day :)...not so.
>
> 1.  there was no hum today, no matter what i tried...decided to
> make the ground lift anyways in case the problem occurs again.
>
> 2.  it's my understanding that on these computer mics, tip is
> signal (and has a voltage riding on it), ring is unconnected, and
> sleeve is ground.  when i try to lift the ground, i get terrible
> sound, until i reconnect it.
>
> is it merely that the headset mic cable is too long for the
> shield not to be grounded (it would be ideal to lift it right
> next to the microphone, rather than at the plug end)?  or am i
> missing some fundimental things????
>
> any help (as always) is appreciated.
>
> deknow
>
>