I broke out the synthesizer and ran a sine wave into the ETI Hyper Fuzz, and examined the output on the Mordax Data. I think the fuzz tone is good the scope view is not super exciting, looks like a strong square wave. Here are a couple pictures.
Switch in the down position.
Switch up
Where is the intermodulation? This diagram promises something akin to wave folding. Could be this diagram is not accurate? The sound is a strong square wave, its got a lot of DS-1 in the sound.
I’m not hearing an octave or ring modish sounds. The three wave forms shown here show really drastically different waves. The output on the scope doesn’t really suggest anything close.
Could be that the input is still too hot? I tried reducing the level of the input, and the output wave form didn’t change.
Is the diode ladder working? What are all of those diodes doing anyway? What is the maximum output of IC1_A?
I tried mocking up the op-amp and clipping sections in the simulator. Follow this link and try it for yourself: ETI Hyper Fuzz Simulator
I made some changes to the simulator. I dropped the input transistor stage. Seems like the original could be simplified a little more and still keep what’s important to the sound of the original design.
This worked pretty well and shows wave folding I expected to see. This image shows the switch in the center position. This position is closest to classic clipping.
The switch in the down position. Here the intermodulation shows as that squiggle at the beginning of the wave.
And the switch in the up position. This looks like wave folding, with that sort of bat shape.
The simulator is showing what I expect. Not sure what the difference is with the actual circuit I built. Something is not the same.
This circuit needs some more experimentation. I can’t really see any reason It even needs the transistor stage? Seems like driving the first op-amp harder just pushes the output into a hard square wave.
The bias network is a little weird. It generates about 3.7V, rather than 4.5V. I’ll guess this has something to do with the choice of op-amp, though it might also have something to do with that crazy diode network. I’m not sure.
One are I haven’t experimented is using difference op-amps. This something easy to try. If anything comes out of it I will be sure to write about it here!