I have designed a front panel will almost all features , including the Mic/line preamp and additional quadrature VCO ouptuts , see bellow for a description of this extension.

 

The Dome filter part selection

Here are R and C values i have used for the dome filter , as specified by JH documention.

 

Quadrature VCO ouptuts

I have added a little buffer amplifier with a gain of 2.5 to output internal quadrature VCO triangle waveforms (0 and 90° phase ).

Schematic of the dual buffer for the Quadrature VCO ouptuts (gif)

Buffers inputs ( J5 , J7 ) are wired to the JH-FS1A mainboard as described on the picture bellow

How it look in reality...

and scope view of signal available on the 0° and 90° output jacks

Quadrature VCO triangle outputs in X/Y mode

 

Front panel

Download Papareil Synth Lab's front panel design for the JH-FS1A MOTM 2x5U size (FPD file)

photoshop simulation

and the real one

The quadrature VCO outputs extension board was not yet installed when i took pictures...

 

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