Discussion about the Korg PolySix synthesizer

personally i'd look at checking out any op amps etc in that particular circuit after it branches off - could also be a bad joint or flakey/noisy resistors or caps... here's a pretty cool little project to scope such things out.

Troubleshoot Electronics FAST with a Super Probe

 

personally id only use the headphones out for the vcf in (distortion) :) But for a cleaner polysix sound one could disable/bypass the LM13600 op-amp that acts like a sort of a low pass filter, its on the effects board and can be (un)done with a fairly simple hack and non-destructive mod, just look it up here: http://synthhacker.blogspot.nl/2013/07/polysix-bypassing-post-effects-vcf.html

Sorry, but the after dynamic effects low pass is intended as a
noisereduction for the effects section. It may happen that its cutoff is
set too low due to the deviation of the caps values. In this case you
may reduce C67 and C72 to 360p or 220p. But I would never bypass them,
because this will increase the noise significantly when the effects
section is enganged and no notes are played.

Thanks for the cap reduce info, will look into that. One could also bypass the effects entirely or put a LM13700 instead all are options subject to taste. I wonder btw did doepfer fix the BBD clock generator noise in the (tapped) bbd A-100 modules? This might also be a good Question for the Doepfer group that we also post in :)

Am 22.12.2016 um 12:00 schrieb ninonine@xs4all.nl [PolySix]:

> Thanks for the cap reduce info, will look into that. One could also
> bypass the effects entirely or put a LM13700 instead all are options
> subject to taste. I wonder btw did doepfer fix the BBD clock generator
> noise in the (tapped) bbd A-100 modules? This might also be a good
> Question for the Doepfer group that we also post in :)

That "noise" is intended. See http://www.doepfer.de/A1882.htm

"A voltage composed of the manual delay control, CV1 and CV2 is
available at the CV out socket, e.g. to control an external clock
suppression filter as the A-188-2 is not equipped with such a filter
(same as for the A-188-1 <http://www.doepfer.de/A1881.htm>)."

and additionally from the same page:

_"Important note (especially for A-188-1 users)_: /The A-188-1 uses
single BBD circuits, which can be adjusted to minimize the clock noise
as the outputs of the used BBD circuits are symmetrical (for details
please refer to //A1881_adjustment.pdf
<http://www.doepfer.de/service/A1881_adjustment.pdf>, trimming
potentiometer P10). By way of contrast the BBD circuit used in the
A-188-2 (MN3011) has six asymmetrical outputs that cannot be adjusted to
minimize the clock noise. In addition the clock noise of the six outputs
adds up. From there the clock noise of the A-188-2 is more intense than
of the A-188-1. This is caused by the properties of the MN3011 but not a
mistake of the module ! If you feel that the clock noise is too much you
have the right to return the _unused_ module within 14 days (i.e. the
module has no scratches or prints, e.g. from srewing into the frame)."/