FatMan and PLL

Scott Gravenhorst, Synthaholic chordman at ix.netcom.com
Thu Oct 5 04:16:37 CET 1995

After reading John Simonton's post about the LED mod to allow the VCOs 
to run much closer in frequency without locking, I tried it and it 
worked very well.  You can get a real slow phase effect.

However, if you have built or will build the PLL addition to the 
FatMan, the PLL causes interference in the form of the VCOs locking to 
the PLL signal, apparently via power supply coupling.

I solved the problem by building a separate -12V power supply for the 
CMOS logic.  Simply copy the -12V supply circuit in the FatMan 
schematic.  I used a separated transformer as well.  I plug both wall 
warts into a switched outlet bar and control power from the outlet bar.

All interference is eliminated in this manner.

Sorry for any inconvenience.

-- Scott G., Synthaholic

There is no 12 step program for synthaholics.  Thank your Superior Being.

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