I saw the Hainbach video on this weird stereolizer module from 1977. There are WAY better mono-stereo expanders/spatializers nowadays, but as the sound was very interesting (and slightly nauseating), I got interested in trying to remake this “Hainbach nauseator”. I tried to check if there is a schematic for this circuit and found a very nice maintenance manual. So this is a quick weekend project to update the old schematic to a more modern circuit design with more common resistor and cap values. I’ll see if I end up building this at one point.
The original schem (look how simple and well drawn it is!):
I removed the output driving circuit as it is unnecessary for most applications. Power supply is bipolar in original, so this cornverts nicely to Eurorack/Kosmo!
There is probably some more optimal value choice for the active phase shifter circuit around U7 (IC2A in original schem). This should overall be less noisy, as resistor values are smaller than in the original and better opamps exist. I simulated using OP227, but any modern opamp should be fine, as feedback resistors are scaled to be 10k. If one needs to drive headphones with this (not that I would recommend that), the U5/U6 can just be a OPA2134 or other opamp with good driving capability.
The output response peaks at around +6,5dB, left and right outputs summed to mono is unity gain (so no input gain pot is technically needed). R9 and R12 adjust the notch positions, and could be potentiometers of about 10k to 50k (original uses linear, logarithmic could be slightly easier to adjust). The input circuitry before U1 is missing here to keep the simulation more stable.
And here is how it looks when varying the separation, notches/band boosts appear:
Also as a bonus here is single notch version that I made before the proper circuit while thinking the circuit driving IC2A was unnecessary (I just had drawn the connection to wrong spot and therefore it did nothing to the sound). This could still be useful for some sound design, as it has Hainbach friendly bandpass (and notch) output.
