Frequency Central Whiteface Build Documentation

Frequency central
Build documentation for:
Whiteface
Based on the legendary ARP 4023 VCF often found within "whiteface" ARP Odyssey Mk1.
I've engineered out the rare parts and the need for matched transistors for the CV input section by
using a Roland style circuit there instead, no change to the vibe though! The audio path remains
pure ARP, with one exception. Built stock from the schematic, the resonance would clip like a
motherfucker above 3 o'clock, in a way which is neither musical or desirable. I've come across a
couple of other versions which have this 'don't turn it up past 8' trait. I've engineered that out - a
single resistor values change. Now resonance is usable and musical over the entire range. As we're
bringing part of a hardwired synth to modular, it's also necessary to buffer the output. I've used an
inverting buffer, which also adds a bit of gain to bring it up to modular levels. A nice side effect of
the inverting buffer is that if you mix the input signal with the filter output, and find the sweet spot,
you can do highpass filtering too!
Key to PCB screen print:
n: This signifies NPN BC547 transistors. Note the correct pinout as shown by the half circles.
p: This signifies PNP BC557 transistors. Note the correct pinout as shown by the half circles.
f: This signifies 2N5485 FET. Note the correct pinout as shown by the half circles.
The PCB shows the correct orientation for BC547/BC557/2N5485. Other transistor types can be used
(eg 2N3904/2N3906), but please observe the correct pinout.
Please observe the correct polarity of the electrolytic capacitors.