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⬅️ Previous capture (2023-01-29)
-=-=-=-=-=-=-
100uF
microphone, o--------||-----------+---------+--------+----o to pin 1
CD,tape player etc. + < | | on GS 7 pin
> 10K | | sound
+-----------+ < | | connector
| | | \-+-\ -+-
+ < | /_\ /_\
= 3V battery ><--+ | 5V | signal
- < 10K pot |Zener | diode
| | | | 1N4148
shield o-----+-----------+-------------+--------+-----o to pin 2
(analogue ground)
on GS sound connector
The Ensoniq is designed to handle 0 to 2.5V input, but audio sources
usually swing equally +/- about zero. Therefore we need a level
shifter, to put the appropriate DC bias onto the input. The 3V
battery and the 10K pot are for this. To stop the low internal
impedence of the battery effectively shorting the sound source, I've
included another 10K resistor. The easy way to set this up is to use
a program like AudioZap and, with no input connected and set the
centreline of the oscilloscope display to be halfway up the screen.
The zener diode is to clip the top of spikes to limit them to about
5V and the signal diode is to clip any negative going signal to
-0.6V. This is protect the Ensoniq chip from overload. The capacitor
keeps the DC out of the source. Pin one on the GS connector is
closest to the front of the computer (ie with the expansion slots at
the back). The Ensoniq has a fairly low input impedence (about 5K),
but most portable cassette or CD players should be able to handle
this, since most headphones have a much lower impedence than this
(usually around 50 to 100 ohms). You can use a tape deck as an
"impedence buffer" for a microphone.