# How to regulate voltage into two variable outputs?

I'm thinking of building a control voltage generator for a synthesizer. Basically I want to control two pitch control voltages with variable resistors, something like this: R1 needs to control only the output of CV1, and R2 only the output voltage of CV2. But with my understanding, if one were to modify the value of R1 this would change the output voltage of CV2, which is obviously undesirable for a pitch control.

Two voltage regulators in parallel seems like overkill for such a simple problem, and I'm not even sure it would work. Is there some other way to make it so that R2 will not affect the output of CV1 and that R1 will not affect the output of CV2?

also, apologies in advance if this is a duplicate question. It seems like a simple, common problem but I've searched quite thoroughly.

• Please explain more... Apr 12, 2015 at 10:53
• It'd be worth adding circuit of the pitch control or how much current the control voltage needs to be able to supply. You probably want the pots configured as a voltage divider by connecting across the supply and using the wiper as the voltage output. Apr 12, 2015 at 11:06
• Couple of issues you may have with this, depending on what you are using it for - the human ear is extremely sensitive to changes in pitch, so you may find an ordinary pot is much too coarse an adjustment to get an accurate repeatable pitch; also pickup of 50/60 Hz mains hum on your CV line can modulate the pitch, which can manifest as anything from a sort of muddy quality to the sound to a distinct buzzing modulation. Apr 12, 2015 at 12:09

Is this what you're after? The outputs will be independent of each other. In your circuit, they would also be independent, but depending on the circuits cv1 and cv2, the voltages may not end up how you think they should be.

This circuit will work assuming CV1 and CV2 are just meant to receive voltage signals; if they draw current then the voltages will fluctuate. How much current will they be taking? And will it vary? You can add a couple of transistors if needed. I can give you the schematic for that if you want. But again, what transistors you need would depend on the current your CV1 and CV2 circuits will draw. simulate this circuit – Schematic created using CircuitLab

Also, depending on how stable you want the voltage to be, you might want another method. But I think this would be the cheapest way of doing it.

• Thanks! Both answers here are just what I needed. The current drawn by the CVs depends on the synthesizer but it is usually quite low so this should work. Apr 12, 2015 at 12:05

It would be useful to have voltage regulation but you do not need separate regulators . Here's a simple circuit based around a single 78L05 (L = low power) which can be expanded to more outputs if required by adding extra fixed and variable resistors. The fixed resistor (R1,R2 etc.) sets the maximum voltage at the output. This should give a value of just above 4.5V but if the output voltage is too high or low it is easily adjusted.

C1,IC1 and C2 form a simple 5V regulator circuit. R1/VR1, R2,VR2 for simple voltage dividers. Depending on your requirements the variables can be linear or log.

You might also want to add a small capacitor between the wiper and ground (say 0.1uF) to reduce any wiper 'noise'.