choosing pots and debugging.

[jogina111]

0.047uf  for 18v and 100uf rated for 25v

[Jdansti]

And what's the transformer's secondary voltage?

BTW-I assume the +/- on the teansformer's primary is an error.

[jogina111]

9 to 12 volts.

[jogina111]

full of problems...I rebuilt it to a smokey amp...and its great...but when I connect  pins 1 and 8, it gives off an infinite  amount of fart noise...could it be the output on pin2. I've seen the ruby amp has the output on pin 3. Help please.

[Jdansti]

Pin 3 should be the input and 5 should be the output. 

Try a 10uf cap between pins 1 and 8 with (+) on pin 1 and (-) on pin 8, and/or a 1k to 5k pot between these same pins. 

Also, make sure you have the 10k resistor from pin 5 to ground. 

Your circuit should look like something close to this (although a polar cap at the input is ok as long as the polarity is as shown):



If you're still having trouble, post the schematic exactly as you have it wired. 

[jogina111]

just a question, what would the 10uf cap on pin1 to 8 and the resistor on pin5 to ground do?

Ive relocated the battery ground wire and the fart sound was gone but if I switch on the connection to pin1 to 8, it sounds like a gay squealing,octave down, and oscillation fused together... Any suggestions?

[artifus]

just a question, what would the 10uf cap on pin1 to 8 and the resistor on pin5 to ground do?

Ive relocated the battery ground wire and the fart sound was gone but if I switch on the connection to pin1 to 8, it sounds like a gay squealing,octave down, and oscillation fused together... Any suggestions?

http://www.ti.com/lit/ds/symlink/lm386.pdf

the cap on 1 and 8 bypasses an internal resistor in the chip and changes the gain from 20 to 200. the resistor and cap on pin five are a filter to tame high frequencies.

[Jdansti]

+1

Also, the capacitors on pins 5 and 7 as shown on the schematic I gave you and on the datasheet that Art referenced help prevent oscillation.

Do you have these capacitors in place?

[jogina111]

not yet..im gonna put that in tommorrow...I saw a smokey amp mod and it has a 100uf cap from +battery to ground, what was that for?

[Jdansti]

That's to filter out noise from the power supply.