Frequency Central has today released Whiteface, a new voltage controlled analog filter for Eurorack based on the ARP 4023 filter found in the “whiteface” Odyssey MK1 Synthesizer.
Besides the classic cutoff & resonance controls, it comes with two audio inputs as well as two CV inputs.
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!
Frequency Central Whiteface is available now as a PCB & panel set for £30 GBP and as fully assembled module for £140 GBP.
More information here: Frequency Central