Cheap n' Easy Pseudo Ring Modulation

[DougH]

From a couple earlier ring mod threads, I took Mark Hammer's suggestion of modding a modulation pedal to do "pseudo" ring modulation. I had an old Boss BF2 flanger lying around collecting dust so I thought I'd give it a try. The idea is to increase the LFO frequency (rate) up into the audio range. This then sort of acts like the carrier in a ring modulator which produces the weird sum and difference harmonics.

The BF2 was a good candidate as I don't use it at all anymore. IMO it's pretty ho-hum as flangers go. For those following along at home, here's the schematic and layout for it: http://www.hobby-hour.com/electronics/s/boss-bf2-flanger.php

The mod is super simple and it's a real easy pedal to work on. Four screws and you're in- and the PCB is not mounted either. C27/C28 are a series pair of caps that control the rate. They are right on the edge of the board, real easy to find. I replaced them with a .47u box film cap soldered to the two outer pads. The inner pads are just used for the stock caps (a series pair of 2 33uf electros) and are not needed if just using one cap. I had experimented and liked this value the best.

The rate control now takes it from a fairly fast flange up into the ring mod zone. I set the "manual". "depth", and "rate" controls high while keeping the "resonance" low for the best "ring" sound. Lower rates can yield a pretty decent approximation of the Black Sabbath "Paranoid" lead sound. Higher rates, just below max, produce more of a "clang", which incidentally works real well (along with other fx) in producing an "electric piano" sound similar to the EHX video demo posted in the lounge

This is not a super intense sound, like some of the demos you may have seen. I've got a couple CA3080A's on order to build a Frobnicator for the real thing. But it does what it does very well, and is super simple to try.

[dthurstan]

Cool idea.

I had a thought a few weeks back if you increase the rate on a tremolo (say the Boss TR-2) into the audio range you would create ring modulation. Am I correct in thinking this is a more accurate form of RM as RM is amplitude modulation using a carrier in the audio spectrum?

[Mark Hammer]

Insomuch as the TR-2 uses an OTA to vary the volume level, yes.

The pseudo-RM thing can really be applied to just about any modulation effect.  Presumably, it produces something different in each instance, but the "rubber-band" aspect is audible and characteristic in every case.