Phasers, what’s not to like. I remember hearing synth strings through a phaser as a kid, probably on something like Oxygene, and thinking “what the fuck is that”. They’re probably one of the sounds that got me paying attention to electronic music.
Nowadays, of course, that sound is a ’70’s/’80’s cliche, but I still love it. So, I built this – the Frequency Central Continuum Phaser II.
Phasers are, as FC describe, allpass VCFs. This one is built around the ubiquitous LM13700 transconductance amplifier that you’re bound to come across in synth DIY at some point.
It’s a straightforward through hole build, very clearly laid out, and with a build guide on their site documenting it. If you’ve built any other FC stuff, or any other through hole module, you can probably build this.
I find I’m much more likely to get distracted with through hole builds, and managed to get the 15K and 1k5 resistors the wrong way round, so the frequency knob and CV range was about 1/4 of what it should be, with a dead spot for the rest.
Rick Holt from FC kindly sent me the schematic, and logical deduction meant finding the problem was easy – the phaser works but the range is off on both the pot and the CV input, so the problem was most likely to be in the CV mixer stage. Bingo, done, and it sounds exactly like an old-school phaser effect should – dirty resonance at the top end, easily dialed back to more subtle phasing.