doubler/ octave divider

Doubler:

Method 1. Put the signal through a "square-law" device -- usually a FET transistor -- that is operating in heavy saturation. Square law means the device essentially multiplies the signal by itself, producing a lot of even harmonics, and the dominant even harmonic is the octave. (Note that most classic octave pedals are distortion devices.) Add some EQ to shape and remix with the original signal.

Method 2. Clip the source signal into a squarewave and use this to phase lock a variable frequency oscillator to the second harmonic of that squarewave. This is called a phase-locked-loop. If desired, spectrally shape (filter) the second harmonic and then remix with the original signal.

Method 3. These days, the octave can be done with digital signal processing to produce more complex effects -- detect fundamental tone(s) through spectral analysis and generate double frequency component(s).

Divider:

Method 1. Clip the original signal into a squarewave and run it through a frequency divider (digital divide-by-two circuit, e.g., a one-bit counter or T flip-flop). This produces a sub-octave squarewave of the dominant tone that may be filtered as desired and also may be remixed with the original signal.

Method 2. Use digital signal processing to do a spectral analysis and then reproduce a signal containing half frequency version of the original. Filter and mix with original.

There is also some signal gating and misc. processing used in each device to reduce falsing and annoying artifacts. And no doubt, there are some other methods I've forgotten. Hope it makes some sort of sense.

-Greg

Thanks -- it's really a bit -- well, more than a bit -- beyond me at the moment. I'm working with a simple amp with dial-in effects. For the life of me, I can't figure out why anyone would use the octave divider. It seems peculiar to me. And the doubler does seem to add more bottom to the sound -- or am I imagining that?

The freq. divider is useful for playing a bass part on guitar -- though it will often sound more like synth bass, than a bass guitar.

If the octave doubler is thickening or boosting the low end, it's probably a consequence of some additional processing that goes into creating a useable or aesthetically pleasing sound.

Thanks for the explanations.

Tim