>anyone tried this yet? scott, you seem to be quite familiar with
>electronics, what exactly does this mod do? why is it connected to the
>power source? and, most important question of em all: how likely is it
>to fry the poly this way? to me the "usual" mod discussed here earlier
>makes perfect sense, since its just replacing the trimpots with ones
>you can turn from the outside - i don�t understand the use od the
>power source here...... well, i think i will be hearing from all of
>you soon.... ;)
I'm not that familiar with electronics really. but I would imagine that the
trimpots control the CVs controlling the cutoff and resonance, and the way
it's normally set up it probably adjusts it from whatever amount to ground,
and the alternative way would adjust it from a positive voltage to ground,
providing a more pronounced effect. So instead of only attentuating the
control voltages it boosts them as well. I guess it would be possible to
blow the filter chip but probably not likely. I don't know the specs of the
chip so I don't know the maximum voltages but the mod doesn't seem too
extreme. As long as it's not exceeding the power supply voltages I wouldn't
see any reason to worry.
So the end result of it is the knobs have a higher range, and the filter can
self-oscillate. BUT the problem with self oscillation on the Poly 800 is
the way the voice architecture is set up. Since there's only one filter, it
goes like DCO > DCA > VCF > VCA. The DCO and DCA are on the oscillator
chip, and the VCF and VCA are on the filter chip. I'm just theorizing here
really but that's what I think is happening. The final VCA seems to open
instantly when you press a key but shuts off abruptly after the release
cycle of the envelope is finished. So the end result of this is that if you
really crank the resonance up, it will self-oscillate but it will continue
to oscillate at full blast until the final VCA shuts off.
At least that's what was going on with mine, or what I thought was going on.
I did the "normal" mod but mine still got to painful self-oscillation.
One interesting note about it though is that if the oscillators and noise
were off, it wouldn't do it, the noise had to be cut on 1 or something for
it to work.
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