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Re: Duh... Q: EDP & CV pedal for feedback control

At 8:04 PM -0800 11/24/98, Sean T Barrett wrote:
>>Only down side is the log taper on volume pedals...
>>linear seems a bit easier to use for feedback control.
>Couldn't the software reinterpret this--apply a curve
>to the input numbers to (approximately) linearize it?

yeah, that would be easy enough. Of course, then you have the opposite
problem with anyone using linear taper pots. So then you end up adding yet
another parameter to allow a choice, and then a lot of time explaining what
this obscure log/linear parameter does....:-)   well, there would be one
problem with this, in that the analog level runs through an a/d convertor
with a fairly limited range. you'd probably end up with some weird
resolution problems in some parts of the pedal range.

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

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 Flint                   | Looper's Delight
kflint@annihilist.com       | http://www.annihilist.com/loop/loop.html
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