Take a look at this

[StephenGiles]

http://www.electro-music.com/forum/viewtopic.php?t=21851&sid=153529ad12cb99f554141ea0c0589c84

[slacker]

Looks interesting, time to free up some space on the breadboard me thinks.

[ambulancevoice]

what ic is a1/a2? just any dual opamp??

[slacker]

yeah any dual opamp should do, in the linked to thread says he used a TL072.

[slacker]

I threw this together this afternoon and it works pretty good.
Basically I built it as per the schematic except it's running on 9 volts using a voltage divider to get a 4.5volt virtual ground instead of using a dual supply.
I made a simple 2 opamp triangle oscillator running at audio frequencies and fed that into one input. The guitar is fed into an inverting opamp stage with a gain of 20, the output of this is directly connected to the other input, no DC blocking cap.

It sounds similar to the other pseudo ringmod/bitcrucher/Nyquist aliaser circuits out there.
It's fairly dirty at the minute and there's some carrier bleedthrough, but I've only spent about half an hour on it, so things can no doubt be improved.
I didn't add the mod part of it but that should make it even more interesting.

Well worth a look.