[sdiy] MFOS Service Bulletin for VCF 24 dB/Octave

[Ray Wilson]

Hi VCF 24 dB/Octave PC Board Purchasers

The resistors I purchased as "1% 1K" and marked "1000" have struck again. As 
I was straightening up my shop I was checking out the 24db/Octave VCF and 
noticed that it too has the resistors (marked 1000) that caused a problem 
with the 12dB/Octave state variable filter. My schematic and parts list 
shows R27, R29, R30 and R32 as 1K resistors. These should be changed to 100 
ohms.

If you have attenuated the input signal and are happy with the results 
ignore this email.

The documentation on the web page is now corrected.
http://www.musicfromouterspace.com/analogsynth/VCFJAN2006/VCFJAN2006.html

The problem the incorrect 1K values will cause is distortion with synth 
level signals and possible early oscillation when the resonance is advanced. 
Please note that the 1K value in the VC resonance circuit is correct (the 
corresponding resistor in the State Variable VCF was not).

Apologies for this oversight.

Ray