potentiometer making weird noise

[Johnsonmusicstudios]

I am wiring a guitar pickup and the volume pot makes a relatively low frequency that gets louder up until about 80% and then goes away when the volume is turned fully up. Could this be a bad pot. What is a likely culprit of this sound?

 

[davelectronic]

noisy potentiometer

Ive come across many noisy potentiometers, most crackle and spit as there old and the carbon track is warped or worn, and the wiper can be warn losing contact, hence the noise, in psu app's it can wreck a supply if not wired properly.

Your noise, all though much not to go on i would think is something else in the circuit making the undesirable noise, take a closer look, coming from the amp ? Dave.

 

[shrtrnd]

Nobody pays much attention to pot construction these days, but in audio circuits,
the TYPE of pot might be an issue.
They're not all carbon wafers these days, there are several different types of construction.
In Johnsonmusicstudios case, I'm thinking davelectronic's explaination makes more
sense. I'm assuming your 'low frequency that gets louder', is at the speaker output,
(as opposed to a signal on an electronic meter). That'd indicate an electronics/amplifier
problem.
(So it may not be the volume pot CAUSING the low freq noise, you just notice it when
you're turning the pot).
You might consider looking at a filter capacitor, or grounding issues, to reduce/eliminate
the low freq sound.

 

[Johnsonmusicstudios]

thanks for the responses guys, i really appreciate it.

however, i know the amp/speaker work perfectly fine. it is the same amp i use with my other guitars and have not had problems with it. last night i was trying to diagnose the problem and found out some new info.

when i cut the pickup out of the circuit, the potentiometer still made the same noises when turned up, also, it is a 250k pot and right now when im testing it, it only goes up to 210k ohms, could this be a sign that it is damaged? i am an amateur solderer and i left the soldering iron on the back of the pot for quiet a while so maybe this could have done that?

Id love to hear what you guys think of this new info as i dont have much circuitry experience!

Thanks!

 

[davelectronic]

Potentiometer noise

Hi again
most potentiometers are +/- 10 - 20 % tolerance, i would try a new, or another potentiometer, as the one your using might have a manufacture fault, or look in to the pick up circuit etc. Dave.

 

[Johnsonmusicstudios]

so the potentiometer is good. switched in a new one and still the same problem.

i have some sort of ground problem :/ i wired just the pickup up to an output jack and found some interesting things, maybe you could explain?

when the pickup is on the floor, it makes a lot of noise, but when i pick it up in the air the noise reduces considerably, and then when i touch my hand to the metal almost all the noise goes away. i understand that is because i am becoming the ground, but what can i do to nip this perminently? :/

 

[shrtrnd]

I'm thinking about this, so I'll mention it for you to consider.
It sounds like the AC hum is being induced into your circuit.
Are you working around a flourescent light, or some other electronically noisy device
while you're working on this? The power outlet tied to some other device that might
be inducing the AC hum onto your circuit?
I'm wondering if you're working on your circuit, and then moving to another circuit when
you're comparing the operation of what you're working on, with other fully functional
circuit.
Just something to look at, while you're working on this.
Some people on this site believe they have insight that I don't intrinsically possess,
so you may have a better suggestion from someone soon.
As a fly by the seat of my pants tech, I'd start experimenting with where your grounds
cancel the hum and where they don't.
Is the cable wire you're using for you new circuit 'shielded' (the wires have an aluminum
foil jacket or wire mesh under the insulation, around your signal wires)? That helps
to keep stray signals from being induced onto your signal wires.
I can't see the circuit, but you're already doing your own experimenting to isolate the
problem. Hopefully, you'll find the solution easily soon.

 

[davelectronic]

potentiometer noise

Hi again
The pick up might have an intermittent earth fault, some component / wire going to ground and it should not be, thats an earth fault possibly causing your unwanted noise, are all your jacks wired and soldered properly ?, it only takes a tiny strand of braid or screen / shield coming in contact with the live feed to cause problems, use a multi meters buzzer to look for good continuity all the way round the circuit, not powered up.

Check the pick up try and get a schematic on line for it, again your looking for component deterioration or an earth fault, test the potentiometer resistance across the full electrical travel, see if the resistance is ok and is what its rated at in ohms. Dave. PS you mention you lifting the pick up makes better ground, is the a wire or components ground a bit iffy, look for an earth fault, or something not grounding properly.

 

[computerlen]

Make certain that the bridge and strings are grounded to the guitar's electrical circuit.