Ringmod fortunate mistake

[Mick Bailey]

A few days ago when trying a few ideas for a guitar ringmod I made a mistake: Instead of the carrier being a fixed frequency (though variable using a pot) the carrier tracked the guitar pitch. Usually a ringmod produces discordant metallic sounds that are difficult to incorporate alongside a regular musical scale, but tracking the carrier maintains a musical relationship with the guitar. When mixed back in with the guitar it produces quite remarkable sounds. I'm still working on the design but will post some video when I get it finished. Just waiting for parts at the moment.

[J M Fahey]

IF you use guitar signal as modulator, you get frequency doubling and TONS of even Harmonics.

Typical Ring Modulators use one "musical" signal (your Guitar) and one very non musical (the modulating oscillator) , so their mix is weird,.

But if both are Musical, including Guitar signal "used twice" results can be way nicer.

I use a very simplified ring modulator thingie in my Bass amps, go figure, to add richer hamonics to a normally very dull and hard to amplify signal..

[Mick Bailey]

I've set up a range control for the second signal that goes from unison to +1 octave (and anything in between), whilst maintaining pitch tracking. I'm also able to transpose both up or down an octave. I'm hooked on this. Because the output is the sum and difference of the two inputs, there can be some really profound bass in there underneath some really delicate chiming notes. I could do with a bass amp and HF horn to fully reproduce the full range.

What I hear with the guitar transposed down an octave some of the sounds may be what you get with your bass amps.

[Mark Hammer]

In general, one needs to remember that the origins of ring modulators lay in the use of very simple waveforms for both carrier and modulator. Typically, they wold have been sine or triangle waves produced by steady-state oscillators, rather than complex waves from a stringed instrument whose harmonic content and amplitude changed rapidly post-pluck. Consequently any ring modulator used with guitar or bass really needs to have some serious lowpass filtering built in, to smooth out the carrier, as well as a modulator that should be as close to sinusoidal as possible.

I will also note that the lower the modulator frequency, the more "pitched" the sideband products will sound. For instance, modulate an A-440 tone with 100hz, and the sideband products of 340 and 540hz will be quite a ways from the input note, and certainly not harmonically related to it. Drop the modulation frequency down to 50hz, and now we're looking at 390hz and 490hz. Moreover, since the sideband products will be arithmetically derived, the higher the note played, the closer to the note those sideband products will be. For an 800hz note, sideband products of 750 and 850 hz will seem fairly close to the input note. Playing up and down the scale will yield a result that still has that "rubber band" sound, but seems to be playable like a scale, rather than pitches that sound near random.

A tracking modulator is a good idea. A barely-audio-range tracking modulator is an even better one. The sideband intervals created would remain constant across the range of input notes, as opposed to getting closer to the input note the higher the pitch/frequency of that note.

[Mick Bailey]

The best sounds I'm getting are sine and triangle waveforms generated from the guitar's pitch. Square, PWM and FM waveforms sound too distorted and lack the chime, especially when mixed back in with the guitar's signal. I'll do some further experiments with modulation frequency and maybe make the carrier range switchable over a much greater range. At the moment the lowest frequency is 41Hz.