[sdiy] Vactrol VCF rev 2: help needed

[mirwin at qouest.net]

Charlie,
My experience with matching individual LDRs (for homemade vactrols) is 
that you need at least 50 units to get a matching set of six LDR's - 
maintaining matching within 20% or so over five or six octaves in a 
filter. You can also try tricks like covering part of an LDR with magic 
marker to raise it's resistance range to help it match the others..

With vactrols, probably the best thing to do is to measure the 
resistance at a given LED current and select the filter capacitors 
individually for each vactrol (so the RC product is the same for all 
units). Also, run the LEDs in series as other have mentioned.
Regards, Mike