Tap tempo controller als frequency multiplier?

[~arph]

Does any of the tap tempo controllers ptap, taplfo, taptation accept a clock input in the audio range? ( it looks like electric druids taplfo2) might ). It would be nice so we can use it as a simple frequency multiplier with selectable rates.

[R.G.]

I'm not sure exactly how you intend this. Do you mean the audio signal is put into the footswitch/tap input, or the clock on the microcontroller?

Actually, it's unlikely to work either way, just at a guess. Having written a few tap temp controllers, what usually happens is that the microcontroller is run at a high clock frequency, 1MHz and up, and it measures the time between taps in some multiple of the clock period. Then it does some math and creates the output waveform from the time between taps.

If you meant the audio is put into the footswitch input, then the microcontroller would measure it as being unmeasurably fast (or nearly so) for most algorithms I've seen. If you meant slowing down the microprocessor's clock to audio frequencies, again the processor would be runnimng so slowly that it couldn't measure the tap interval.

I think a much more useful frequency multiplier is a phase locked loop (PLL) and a divider chip. This really does take the input frequency and multiply it up by the amount the divider divides. A divide by four for instance gives an output two octaves up. A divide by two is one octave up. You can do harmonies, by multiplying, then dividing again. Multiplying by 5 then dividing by 4 gives a fifth, for instance.

For both the uC input (if that could be made to work) and the PLL scheme, you'd have to filter the input down to one tone and then square that up into a logic-like pulse. No chords allowed if you want predicable results.

Or did I misunderstand what you were meaning to do?

[~arph]

I'm not sure exactly how you intend this. Do you mean the audio signal is put into the footswitch/tap input, or the clock on the microcontroller?

Actually, it's unlikely to work either way, just at a guess. Having written a few tap temp controllers, what usually happens is that the microcontroller is run at a high clock frequency, 1MHz and up, and it measures the time between taps in some multiple of the clock period. Then it does some math and creates the output waveform from the time between taps.

If you meant the audio is put into the footswitch input, then the microcontroller would measure it as being unmeasurably fast (or nearly so) for most algorithms I've seen. If you meant slowing down the microprocessor's clock to audio frequencies, again the processor would be runnimng so slowly that it couldn't measure the tap interval.

I think a much more useful frequency multiplier is a phase locked loop (PLL) and a divider chip. This really does take the input frequency and multiply it up by the amount the divider divides. A divide by four for instance gives an output two octaves up. A divide by two is one octave up. You can do harmonies, by multiplying, then dividing again. Multiplying by 5 then dividing by 4 gives a fifth, for instance.

For both the uC input (if that could be made to work) and the PLL scheme, you'd have to filter the input down to one tone and then square that up into a logic-like pulse. No chords allowed if you want predicable results.

Or did I misunderstand what you were meaning to do?

You assumed right. I meant to use the audio ( already conditioned to a square wave ) as the tap input. I am aware of the limitations but i wondered if at 20mhz the algorithm would be fast enough. One could always feed a divided signal to the chip too of course.
It was just a thought, it would be a simple one chip solution. I have done it in the past with a pll and a divider and though it works it can be a bit tricky to set up so it tracks we'll with minimal settling time and requires at least one extra ic.

[~arph]

You can do harmonies, by multiplying, then dividing again. Multiplying by 5 then dividing by 4 gives a fifth, for instance.

Isn't that a major third?

[R.G.]

Isn't that a major third?

... or a minor seventh. One of those. I was never good at musical math.   

[~arph]

Neither am I, but I had just looked up the ratios..  a fifth would be multiply by three and divide by two.