Frequency to voltage

[Teej212]

anyone have experience doing these? ive found a good amount of information, most of it recommending DSP for this conversion, but ive found a lot of data sheets for ICs that have frequency to voltage applications. I know scott from mtl assembly said something about messing around with frequency to cv....

[Schlatte]

You could go the least complicated route and try some FM-Demodulator circuits. Most of them just convert the FM-Signal to an AM-Signal and then demodulate that with a simple Envelope detector (a diode, a capacitor and maybe a resistor). Not exactly accurate, but fairly simple.

FM to AM-Demodulator:
Maybe as simple as a high pass filter (frequency dependent voltage divider), but there are better circuits out there.

AM-Demodulator:


I'm pretty sure it's possible to do a frequency to voltage (CV) conversion that way with a little OpAmp circuit after the AM demodulator to get the output right.

[D-Rainger]

I made this frequency to voltage circuit - worked quite well... The low open E and A strings didn't track well, LED just went bright, but everything else was good!
I think that LM2917N-8 is usually used in car speedometers...

[Teej212]

killer. thanks so much. im one step closer to making my guitar synth!

[D-Rainger]

Wow - that sounds good! Will it be in a pedal...? (Maybe a big pedal?!)
What will it do?
BTW I just got a Pigtronix Mothership, and the frequency to voltage is amazing - synth note can track perfectly in tune with the guitar note. This circuit here, I don't think it follows exactly like that... above A (5th fret on the top -thinnest - string) the LED is pretty much at its brightest. That's when it's set up with a (quietly played) lowest E note giving no illumination at all, and the 1st fret F being slightly on.

[Teej212]

well the goal is to have square, sin, tri, saw VCO. An envleope generator, a filter, im probably going to do the MS-20. and LFO for controlling shit, and a bunch of CV ins and outs. and then a VCA