Cross Modulation

[H S]

Everyone tries to get rid of cross modulation, but what if you want more of it?  Bass boost?  Hard clipping?  Ring modulation?

[Paul Perry (Frostwave)]

Depends what you mean by "cross modulation". If you mean intermodulation distortion (like a chord in a fuzz) then anything you do to make the amplifier stages non-liear (eg by clipping) will help. Boosting in this cdontext is just another way of clipping.

[petemoore]

  It's easy for me to say that the possiblity has interesting possibilities, since I don't know exactly what we're talking about.
   However some interesting stuff might get cooked up along the lines of...creating a signal path that does put enough out to superimpose itself on another signal path.
  Because I've never tried or read about this rambling...
  Take a signal and split it
  Side A gets some usual fuzz or other treatment
  Side B gets octaved [or something], and either:
  Made to be large enough voltage to lay that parallel to a side a [longer?] signal path wire
  Or, have side A pass through a transformer side, through a coil, the other side of the transformers coil gets the side B signal
  Some method [other?] would superimpose say a switched click at the same or multiple of the original signal, through the use of transductance. I hope thats the right word.
  I've either made your original idea more elaborate and silly or possibly some interesting noisemaker could be the result of the concepts presented.

[Transmogrifox]

Make a fuzz face with the power supply to the resistor on the final output stage buffered by an op amp, or emitter follower led by a single transistor gain stage.  In either case, feed an amplified version of the input to the power supply so that the guitar signal is changing its own clipping threshold.  It would be best to inject the signal inverted to the power supply, or in the case of an FF the output is already inverted, so you would feed the input in phase.

This idea of changing the "clipping threshold" is known as a square-law multiplier.

Also, a full-wave rectifier is a squaring type circuit.  For a sine-wave, the rectifier is the equivalent of multiplying the input with a square wave of its own frequency.  Many octave circuits inherently have a lot of intermodulation distortion terms.  The intermodulation is what produces the octave.  Unfortunately for those who want a "clean" octave, there are more terms in the multiplication that don't produce the octave up, nor frequencies at musical intervals, so they often sound very fuzzy.  For somebody that wants that fuzzy sound, a rectifier is a good way to go for increasing intermodulation.

[doug deeper]

try making a ghetto hard limiter bye rnning a super high gain signal trough a germanium diode.
you'll get all sorts of extra info.

[H S]

Intermodulation--that's what I meant.  Thanks for the responses.

[SeanCostello]

Ditto on the full-wave rectifier. Most of the octave-up pedals fed into a second distortion pedal will give you plenty of intermodulation distortion. If you can get your finger tension to be just right, you can get bass notes from the difference frequencies high up on the guitar neck. Beat frequencies galore!

Sean Costello