Cave Troll

What it does

A ring modulator multiplies two signals together instead of mixing them, so what comes out is the sum and the difference of their pitches rather than either of the things you fed it. This one does it with logic: an XOR gate's output is high only when its two inputs disagree, and that is the same thing as multiplying two square waves. Each input goes through a gate of its own first, which squares up whatever you feed it, and a third gate does the multiplying. One chip does all of it.

The Cave Troll used to be a passive ring modulator, and it never did much on my bench. I swapped its insides for my XOR Ring Mod, and it sounds so much better: like a real ring mod, that robotic echo sound.

I played it with two synths, one into each input. It wants strong signals, about a volt either side, because each input has to swing far enough to flip its gate. Synth and oscillator outputs do that easily. The jacks are quarter-inch, the big guitar kind, not the 3.5 mm minijacks on most synths and Eurorack, so a minijack synth needs adapter cables. I have not tried a guitar straight into it, and a guitar may be too quiet to drive it without a boost in front.

One of a kind. When it is gone it is gone.

Demo

Controls

Top jack

An input.

Middle jack

The other input.

Bottom jack

The output. This is the one that goes to your amp or mixer. The jacks are not lettered, so it is worth writing down somewhere.

Toggle

Power on and off. The lamp beside it shows when it is on.

No volume knob

The output is a full-strength square wave and there is nothing to turn it down with on the box, so it is loud. Start with your amp or mixer channel low.