removing condenser mic from a PDA and modifying circuit for

[Mad Scientist Jr]

I have an old PDA that I would like to modify (if possible) by taking
out the built in condenser mic and replacing it with a 1/8" or 1/4"
jack that I can plug another device into. Mainly I want to plug a
standard stereo headphone output (from iPod/cellphone/walkman/etc)
although it would be cool to be able to connect a line-level out from
a mixer, or directly plug a guitar in. The latter ones would probably
require a different circuit so for simplicity I'll just stick to the
first scenario (headphones out). Assuming I successfully can de-solder
and remove the condenser mic from my PDA and have two leads (which
went to the mic) free to solder my new input to, what kind of circuit
do I need to place between the new jack and the leads, so the input
works? The PDA must have some kind of preamp built in to drive the
condenser mic, so I am thinking maybe some kind of resistor or volume
control to "step down" the signal strength before it goes into the
PDA's preamp? I suspect the audio fidelity won't be the greatest, but
as long as it's passable I would like to try. Any info would be most
appreciated... thanks.

 

[jwvm]

On Aug 28, 1:33 pm, Mad Scientist Jr <mad.scientist...@gmail.com>
wrote:

I have an old PDA that I would like to modify (if possible) by taking
out the built in condenser mic and replacing it with a 1/8" or 1/4"
jack that I can plug another device into. Mainly I want to plug a
standard stereo headphone output (from iPod/cellphone/walkman/etc)
although it would be cool to be able to connect a line-level out from
a mixer, or directly plug a guitar in. The latter ones would probably
require a different circuit so for simplicity I'll just stick to the
first scenario (headphones out). Assuming I successfully can de-solder
and remove the condenser mic from my PDA and have two leads (which
went to the mic) free to solder my new input to, what kind of circuit
do I need to place between the new jack and the leads, so the input
works? The PDA must have some kind of preamp built in to drive the
condenser mic, so I am thinking maybe some kind of resistor or volume
control to "step down" the signal strength before it goes into the
PDA's preamp? I suspect the audio fidelity won't be the greatest, but
as long as it's passable I would like to try. Any info would be most
appreciated... thanks.

Lots of luck! The audio input circuitry is almost surely only intended
for dictation. To save memory, the audio is very likely heavily
compressed so artifacts will really destroy any semblance of fidelity.
It also has very aggressive AGC that is great for dictation and
horrible for music. There are probably five other issues that will
further degrade music quality. BTW, the condenser microphone might be
the highest fidelity component in the PDA. How does music sound that
has been recorded with the microphone? It probably won't sound any
better using a hacked line input. You will get much, much, much better
results (and multiple channels) using some like a Zoom.

 

[whit3rd]

On Aug 28, 10:33 am, Mad Scientist Jr <mad.scientist...@gmail.com>
wrote:

I have an old PDA that I would like to modify (if possible) by taking
out the built in condenser mic and replacing it with a 1/8" or 1/4"
jack that I can plug another device into.

Why not just glue a bit of Velcro next to the microphone? A suitable
speaker-on-a-wire can be stuck on whenever you want. It can
be as simple as half a dead iPod earbud, or you can experiment with
matching transformers and/or amplifiers.