Strange GC noise problem

[pacoblackxx]

Hi, i build my first lm3886 amplifier. Everything is ok but..i have a strange problem.

The wire from potensiometer's out that goes to the chip board line-in is very sensitive to noise(for both channels). When i touch them( or moving my hand above them) the speakers make noise.

I had them twisted at first, but a had a noise problem. Then a removed the twisting and the problem gone for a while but today it started again..

My case is wooden and only the top surface is aluminium. When i remove the aluminium the noise is very little, but a can hear it late at night. when i mount the top aluminium surface the noise gets a little more audible, even if no wire is touching it.. I noticed that if i connect pot's in with pot's out (as like no pot is there) the noise almost dessapears...its very hard to hear it even if you are too close to the speakers(2-3cm).

Any recommendations?

[semi932]

No expert but if it were me, I would wire pot from audio out on chip to pot input and out to speakers.

[pacoblackxx]

these are the wires that cause the problem..its a little messy i will fix it soon.




http://img706.imageshack.us/img706/6024/wires1.jpg

this is the aluminium cover..





http://img571.imageshack.us/img571/9646/topvu.jpg

[Redshift187]

Very few pots can handle speaker level currents, semi932.

It sounds to me like the solder points on the pot are bad, specifically the ground connections.

[star882]

You could use a wirewound potentiometer, but it would be a very inefficient way to control volume.

[sangram]

The input to the chip board should be from the middle leg of the pot, you have it miswired

[mjf]

hello.
do you have a central ground point (star ground) ?
have you connected the alu cover to this point?
has your pot a metal case which is not connected to ground?
........and you can use shielded wire from pot-out to chipamp input.
greetings

[pacoblackxx]

Originally Posted by sangram

The input to the chip board should be from the middle leg of the pot, you have it miswired

Are you sure?? I have the line-in in the middle, not the chipe signal-input. is this problem?


The star ground point is on the wooden case. And no, i haven't connected the aluminium cover to the start ground...Is this nessesary?

[sangram]

I've had chipamps in open air without case and never experienced noise problems.

The pot is always wired with signal to pin 1, amp's input to pin 2, and ground to pin 3. This way the input starts off short-circuit (no signal) and goes to full output (full signal) as the pot rotates clockwise. The way you've done it, the amp input starts off by seeing an open resistance and the line-in starts by seeing a short-circuit.

With the shaft facing you, the left most is pin 1 and right most is pin 3. Pin 2 is the wiper.

[pacoblackxx]

Originally Posted by sangram

I've had chipamps in open air without case and never experienced noise problems.

The pot is always wired with signal to pin 1, amp's input to pin 2, and ground to pin 3. This way the input starts off short-circuit (no signal) and goes to full output (full signal) as the pot rotates clockwise. The way you've done it, the amp input starts off by seeing an open resistance and the line-in starts by seeing a short-circuit.

With the shaft facing you, the left most is pin 1 and right most is pin 3. Pin 2 is the wiper.

hmmm i changed the wires as you told me and there is no sensitivity anymore!oh yeah baby. A will wait until night where my room will be very silent, so i can hear if there is any noise.

But the sensitivity is gone for sure! thnx mate