Discussion about the Korg PolySix synthesizer

Hi,

    On the PolySix, the DAC output is linear.   Every step is a semi-tone.   That voltage is 
converted into an exponential one for the oscillators by the anti-log circuit.  (which includes
the opto-coupler of course)

    If all of the oscillators show the same poor tuning, then the problem is in the anti-log
circuit, or in the S&H (4051) at its output.   

    I uploaded a procedure a while back to the files section for adjusting the anti-log
trimmers.   You could also use that to help measure whether the anti-log is working 
correctly with just a voltmeter.   If the trimmers have been messed with, then you will
definitely need to re-calibrate it.   

   Also I uploaded a re-drawn schem of that circuit so you can see a little better how 
it works.

     Bob Grieb


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On Fri, 7/24/15, jacklane@sbcglobal.net [PolySix] <PolySix@yahoogroups.com> wrote:

 Subject: [PolySix] Re: tuning issue still... / local repair STL
 To: PolySix@yahoogroups.com
 Date: Friday, July 24, 2015, 9:57 AM
 
     
       
       
       Thanks Tony! Unfortunately the octocoupler has
 already been replaced.  So we can rule that out. Both sides
 of the  board have been thoroughly cleaned and all the
 traces redone everywhere that the battery acid leak
 occurred. I am open to other thoughts / suggestions you or
 anyone may have. I am even half tempted to by a kiwi six
 replacement board and power supply If could be sure it would
 fix these issues but would hate to drop that kind of money
 and still not have the P6 fixed.... Jack
 
     
      
 
     
     
 
 
 
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