help on debugging and pot selection

Started by jogina111, August 22, 2012, 12:34:25 PM

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jogina111

ok, I built this amp and It
works great. But it got no
volume control.. Im gonna put
one but I dont know how
much pot resistance I should
use and where to put it.. Please help me.. Also, the amp
is great but
theres so much humming
when I turn it on, what could
the problem be? Heres the
schematic: www.ultimate-guitar.com/forum/attachment.php?attachmentid=106549&stc=1

knutolai

Try a 1M log potentiometer. Put it between pin 5 og the IC and the tip of the output jack. (lug 1 to ground, lug 2 to outpuck jack, lug 3 to pin 5 of IC). ;)
Now about the humming.. This is a really really really simple amplifier and (this is my guess) hum is what you get when you stick with the dirt-simple solution!
If you want to build something just a little more complex check out the Ruby amp at runoffgroove! just 10-15 parts and relatively amazing sound quality!! ;)

Hope this helps!

Goodrat

Yeah, but this drives a speaker directly. I usually use a FET, then a tone control, to a volume, then the 386.
But try the input jack to the top of a 10K pot, other side to ground, wipper (middle) to C4 if you must stick with what you got.
http://www.hobby-hour.com/electronics/lm386-power-audio.php
The example link uses the other input.