Sunday, 26 November 2017

Phasers To Stun

I decided to test out various Notch Filters around the studio the other day. I really like the way notch filters sound - like a weird phaser. In fact some so-called phasers are done like this - for example the one in the Polyfusion system I have got. Its not real phasing, but it still sounds cool. The principle behind it is this: use a high-pass and a low-pass VCF in parallel and set them so they create a notch (see diagram below). The key to it is how they frequency shift. On some of my modulars (the ARP 2500, Moog 3C and the Emu) there is a notch filter provided, but on the others its just a case of patching together a HPF and LPF and sending an LFO to control their cutoff frequencies. The CV going to the frequency of the LPF is positive and it needs to be inverted to control the cutoff frequency of the HPF so that the notch moves up and down correctly. With some trial and error I managed to get some quite nice phaser-action happening don't you think?