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?
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?
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No expert but if it were me, I would wire pot from audio out on chip to pot input and out to speakers.
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
An externally hosted image should be here but it was not working when we last tested it.
http://img706.imageshack.us/img706/6024/wires1.jpg
this is the aluminium cover..
An externally hosted image should be here but it was not working when we last tested it.
http://img571.imageshack.us/img571/9646/topvu.jpg
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.
It sounds to me like the solder points on the pot are bad, specifically the ground connections.
You could use a wirewound potentiometer, but it would be a very inefficient way to control volume.
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
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
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?
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.
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
Cool, enjoy. I would still clean up the wiring a bit tho, some of them are a little longer than needed.
Good Luck 🙂
Good Luck 🙂
Chip volume
Also, wire lengths should be short and neat, and if a ground plane board is used, the wires (bundled) should be tightly run along the surface of the board. In some cases it should not touch the board, but it is easy to find the correct way (less noise).
You could use fixed resistors in the NFB network for volume too.
Also, wire lengths should be short and neat, and if a ground plane board is used, the wires (bundled) should be tightly run along the surface of the board. In some cases it should not touch the board, but it is easy to find the correct way (less noise).
You could use fixed resistors in the NFB network for volume too.
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