Subject: Re: j25 on 2gs
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Date: 04 Nov 1999 04:45:07 GMT
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"Dean W. Nehring" <lauren@netins.net> wrote:

>what is J25 used for on apple 2gs?

It provides access to the Ensoniq sound chip.  J25
has all the signals needed to reproduce stereo (or
actually up to 8 channels...octophonic) sound and
it also provides access to the Ensoniq's analog to
digital converter (ADC) for digitizing sound.

>have 2gs with connector on jack running
>to small card which is also connedted to fan power supply. output is single
>jack on back of gs. any idea what card is for? audio amp or somthing is my
>idea. regards dean.

It is a microphone preamp.  The card draws power
from the fan connector.  The jack supports a mono
microphone.  The card simply amplifies the mic's
input to the levels needed by the Ensoniq's analog
to digital converter.

If you intend to digitize with this card, use 26360Hz
or half or double that sampling rate.  That's the
frequency of the power supply so using it will
dampen any noise from the power from the fan
connector and result in clean samples.