Blah Blah Cafe, the Jean-Michel Jarre forum

[jarrekid]

Hi,
I'm DESPERATELY looking for a pitch/frequency (say from a guitar) to CV convertor circuit for my DIY modular. Analogue Solutions sell this module but I want to see if I can DIY it before buying something.
Thanks,
Jarrekid.

[GeeJee]

My MS20 has that.

Why doesn't your MS20 emulation?

[jarrekid]

My MS20 has that.

Why doesn't your MS20 emulation?

It's not as though I can use that in my modular synth though is it...

Anyway, I remembered I have a toy "vocoding" megaphone thingy upstairs that can track the pitch of your voice. I might try gutting that and seeing it that will work.

[PHASEREFFECT]

Maybe a using a sort of "counter". First thing would be to convert the incoming signal (sine maybe) into a Pulse waveform, then drive with it maybe a clock divider, feed a 8Bit binary counter with the output of the clock-divider, build a timer-Circuit which sets the counter after a specific time inactive and connect the counter to a DAC. But then is the question, how (and when) should the timer being resetted to enable the next DA-conversion, there must be something like a "compare" between two different (incoming) pitch and/or volume values.

I´ll take a look what i can do.

Stef

[jarrekid]

Maybe a using a sort of "counter". First thing would be to convert the incoming signal (sine maybe) into a Pulse waveform, then drive with it maybe a clock divider, feed a 8Bit binary counter with the output of the clock-divider, build a timer-Circuit which sets the counter after a specific time inactive and connect the counter to a DAC. But then is the question, how (and when) should the timer being resetted to enable the next DA-conversion, there must be something like a "compare" between two different (incoming) pitch and/or volume values.

I´ll take a look what i can do.

Stef

Well, with a bit of research, there are already F/V (freq - volt) converters, but these are mainly used in cars. However, it seems that I can still use them:
This might work, the LM2917 seems to be the IC to go for

[PHASEREFFECT]

Don´t know. The question is, how this circuit would react, when the voltage of the input frequency itself fall down. Other question is, which sort of frequency this device allows. Me thinks, since it is used for tachometer and switching applications, it only accepts a pulse waveform for input. Third question is, if the output signal is really a straight voltage or maybe pulse-width modulated (see LED stop-lights on modern cars, they work with this method). Measuring devices and LED´s are slowly-acting, they don´t care about the input signal. A Synth would maybe recognize this signal as an external waveform instead of a control voltage. Fourth question is, if this device accepts the same capacitor / resistor value for the entire frequency range from 0-10KHz, which i strongly doubt.

Have found something other:

http://www.wiseguysynth.com/larry/guitar/PAGE1.gif

Take a look to the right side upwards to the Q22 circuit.

Greetings
Stef

[jarrekid]

Ok, I might email this guy to see if he just has the F/V circuit.
Thanks,
JK