[sdiy] what opamp for "warmth"? (I know, I know...)

René Schmitz synth at schmitzbits.de
Fri Apr 7 13:51:12 CEST 2023

You'll find the same VCA in the 909 in a few places. (Bassdrum , Toms, 

Note how far the signal is divided down.

It's noisy, and nonlinear, and has some control feedthrough. Show what 
you can get away with for a single monophonic signal.

The MS10 had the single transistor, the early "Korg35" MS20 had the same.
The later MS20 had a second transistor, which makes things more 
linear/symmetrical and you can run larger amplitudes -> less noise.

According to the schematics the transistors shall be selected. jx3p also 
says "SEL".

Anyone would know what for? Equal gain?


On 07.04.2023 11:04, Adam (synthDIY) wrote:
> David G Dixon via Synth-diy pisze:
>>>>> Whatever the VCA is in the Korg MS-20 really warms up the sound of 
>>>>> that synthesizer.  You can find the schematic on the internet.  I 
>>>>> have something redrawn by a fellow named Marjan Urekar that I 
>>>>> looked at years ago.  It involves two transistors.  It is 
>>>>> evidently also the VCA used in the Roland JX-3P.
> Interesting.... here's the JX3P version
> grab 2023-04-07 at 6.57.54 pm.png

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