Discussion about the Korg PolySix synthesizer

Dear Tony,
 
YES!  Please count me in as one who would LOVE to implement that 3ms gate delay.
 
And as long as I have your kind attention, if you have any other suggestions for improving the Polysix (or Mono/Poly), I'd love to know about them as well.
 
Thank you so much.
 
Dave Garfield - Colorado, USA

From: Oakley Sound <oakleylist@btinternet.com>
To: PolySix@yahoogroups.com 
Sent: Saturday, February 9, 2013 3:38 AM
Subject: Re: [PolySix] Key Assigner Logic and Timing

  
Whatever you do you should ensure that the gate signal that drives any 
particular envelope does not arrive before the new pitch CV is presented 
to the VCO. The stock Polysix exhibits an annoying trait in that the 
first three voices are actually triggered before the pitch CV is updated 
to the new note. Hence, with patches that use a fast attack, the first 
three voices click slightly if the difference between the previous note 
played on that voice is significantly different in pitch to the new note.

The difference in time varies per voice but voice two has the worst 
delay with gate being applied 2mS *before* the CV. Voices 4, 5 and 6 
have their gates applied a good 2mS *after* the CV is updated so do not 
click. 2mS might not sound that much but it's enough to produce an 
audible click particularly if the patch is one with low harmonics.

I had thought this was an offset error or bleedthrough problem within 
the voice VCA. But the randomness of the clicking led me to look 
elsewhere. All the polysix units I have seen exhibit this problem and, 
indeed, it's even audible on the many Youtube demos.

A quick way to test this is play is choose a patch with a fast attack 
and fast release, no EG sweep to the filter and set the filter to a 
dullish sound. Press the top C note six times to load the highest note 
into each voice. Then press the lowest note on the keyboard six times. 
You should hear three of the voices produce a noticeable click while 
three of them don't. Continuing to press the same note again will not 
produce the same clicking because now the voices don't have to change 
pitch. If you can hear an appreciable click still you need to adjust the 
VCF offset but that is a different problem.

If one is designing the key assigner from scratch one should able to 
avoid this problem by writing the pitch information before any new gates 
are sent out from the latches.

If you have a stock Polysix you can do what I have done and that is 
build a triple gang gate delay circuit from a handful of components. 
This delays the gate signal for around 3mS and completely silences the 
pre-note glitching. I'll pop up a schematic at some point if any one is 
interested in doing it themselves.

Tony

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



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