Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

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Subject: RE: Temperature of YOUR Polysix?

From: <chipaudette@yahoo.com>
Date: 2013-11-21

Hi!


Chip here, the one from the synthhacker blog that you referenced.  To answer your questions:


Re: R166 (the 1K resistor not being present), I just looked in my synth...mine is also missing.  Interesting.


Re: R167 (the 33K resistor maybe not being 33K), mine is colored orange-orange-orange, which is 33K, as specified.  When I measure it in-circuit with my DMM, it is only indicating 4K or so.  Since the color bands clearly indicate 33K, the lower reading must be because the in-circuit measurement includes parallel paths through ground or something.  Your own evaluation of R167 might be seeing the same effect.  What were the color stripes on R167?


Re: R168 (you didn't ask, but it the 22K that the 33K is jumping around), my R168 is red-red-orange, which suggests 22K as indicated on the schematic, but it is only reading ~5K in-circuit.  So, again, in-circuit measurements can be funny.


If you've been checking out my frequency-response mods, don't miss the others that I did after this one:


Bypass the Post-Effect VCF to open up the sound: http://synthhacker.blogspot.com/2013/07/polysix-bypassing-post-effects-vcf.html


Deeper Bass (Based on Tony's Discussion): http://synthhacker.blogspot.com/2013/08/polysix-deeper-bass-bypass-c61.html  and be sure to read it's follow-up posts.


Flatten Treble Response: http://synthhacker.blogspot.com/2013/08/polysix-flatten-treble-response.html


Good luck!


Chip

 





---In polysix@yahoogroups.com, <terje.winther@...> wrote:

OK folks,
I have followed the discussions on the Polysix mods, and I am in the process of implementing them into mine.

First of all: on my P6 the R167 (in the effects PCB) is neighter 2.2K (as Korg stated they were in the "old production") nor is it 33K as stated in the service manual schematics (I hope there is only one version of the service manual).
On my P6 the R167 is 4.7K.

Secondly, in the schematics, and is what you describe, there should be a 1K resistor in parallell to R167. Well: there isn´t. Not on my PCB anyway.
You do state that this was only in theory, and that you liked the bright sound, so you never did remove the 1K resistor. Did you ever find it on the PCB?

And then, from what Tony says (below):
By "CE" do you mean the C84 ceramic cap?
By "C78" do you mean that cap belonging to IC17? That doesn´t seem right - you might mean C79?

My P6 is all completely apart now, so implementing any mods is easy at this stage.

Terje



Den 18. juli. 2013 kl. 14.04 skrev Oakley Sound:

 

> Cut that 1K resistor (the upper one, not the lower one!) and you'll
flatten the high frequency response!

Steady now. The actions of the mod that Korg introduced in the later
models also applied additional changes to the feedback around the final
op-amp. The actions of CE and C78 should also be considered - the value
of CE may be enough to de-emphasize the increased brightness due to the
1K resistor. C78 is interesting because its action will be dependant on
the gain of the OTA.

I looked at the overall response of the whole output stage on my P6 by
sweeping a single note's resonating filter across the whole audio band.
I didn't see any major change in amplitude over the audible range.

Tony

http://takla-makan.bandcamp.com/
http://www.oakleysound.com