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Help with noise from potentiometer

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Newbie level 1
Sep 9, 2007
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potentiometer impedance noise

Hey everyone.

For school im making an audio based project and i have an audio signal running through a potentiometer to an amp i made. When i do this though, i get a huge amount of noise coming out the amp, unless the pot is at minimum resistance (effectively removed from the circuit).

- The amp works fine without the pot in the circuit.
- The pot works fine, ive tested it on a CRO.
- Ive tested several different pots (motorised and not) and the result is the same in all.
- All the wiring and soldering is good quality and im confident it isnt the cause.

Can anybody offer a suggestion on how to remove this noise.

Thanks alot ~ Matt

dc noise from potentiometer

What kind of noise?

Try using your oscilloscope to identify the type of noise and to locate its source.

Maybe the wires to the potentiometer are too long, causing crosstalk or feedback. Maybe your amplifier's input stage is unstable, causing it to oscillate over some range of input resistances (potentiometer positions). Those are just wild guesses.

potentiometer noise

Quite often the noise in a potentiometer is created because of DC Voltages on the wiper of the pot.

Try putting an input and output capacitor on the pot to Block any DC signals.

This should eliminate your problem.

Failing that, Show us the Schematic of your circuit.

noise in potentiometer circuit

This must work.



PS. Sorry for quality of picture I did it in MS paint.

Just to remember :

If the noise generated by POT is done while turning the axis, you could reduce it just doing several turns repeatlly in order to remove rust or dirt, if it is not sealed.


Several tips to check:

Are you using the same power source?
If not be aware of any ground loops.
Is the amplifier input high impedance?
If yes them probably you have a big impedance mismatch
causing the pot to pick up the noise.
Is the noise you refering hum noise or what type is it?

Just some guesses for the problem.

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