anyway, for John, here's how to set the trimpot:
*********************************************
This requires that you actually open up the unit, and have it
opened with
the power on. *Please follow appropriate electrical safety rules!!
* If you
are not careful and you fry yourself, please don't blame me!
There's a trimpot on the PCB, near the left side, by the volume
knobs. It's
job is to trim a dc offset from a VCA. Sounds like your's is not
set right
for some reason, which would cause the thump you hear.
To set it you need to run one of the built in diagnostic tests. The
test
basically turns the VCA on and off at about 60Hz, so if there is an
offset
you can hear the resulting tone in an amplifier. (or see it on a
scope,
whichever way you like.) While that's going, you adjust the
trimmer until
the tone/waveform reaches it's mimimum.
To get into the trimmer test, Start the unit while holding the
Parameter
and Record buttons down. Keep them held while the startup screen
goes by,
until the display shows all t's. Then let go. Should say 7F. Press
parameter so the "Keys" LED is lit, then press Insert to start the
trimmer
test.
You should hear a ~60Hz tone in an amp. (turning input volume off,
mix to
"loop", and the output volume up helps.) The tone will change in
level as
you adjust the trimpot. Adjust to where the tone is at it's lowest
level.
(you'll still hear hashy noise sounds, but the 60Hz should become
nearly
inaudible.) After you set the trimmer, pressing parameter again
will stop
the test. Then you can turn the echoplex off and power back up
normally.
**********************************************
kim