choosing pots and debugging.

[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

[deadastronaut]

put a 100k log pot after the 470uf,  

470uf >>>lug 3 of pot.....lug 2 of pot to output.....lug 1 to ground...

as for hum, check the orientation of your electrolytic caps....a pic might help too...

[jogina111]

on the schematic, which is the negative side of the caps? Sorry, Im not familiar with schematibs like these..

[Jdansti]

on the schematic, which is the negative side of the caps? Sorry, Im not familiar with schematibs like these..

The schematic is a bit fuzzy, but it looks like the caps have the arrows pointing toward the negative lead similar to the way that the real caps are labeled.

Also, if you want to be able to vary the gain, you can place a 1k linear pot in series with C1.


EDIT:
As for noise, you might not be able to tell how quiet it really will be until you get it into a metal enclosure.

[Jdansti]

put a 100k log pot after the 470uf,  

470uf >>>lug 3 of pot.....lug 2 of pot to output.....lug 1 to ground...

as for hum, check the orientation of your electrolytic caps....a pic might help too...

Rob-does it matter on the lm386 whether you put the volume pot on the output as you describe above or on the input as shown on the noisy cricket scheme?


http://www.beavisaudio.com/projects/NoisyCricket/Noisy_Cricket_Schematic.gif

[jogina111]

finished refining the amp. Low noise,good distortion but when i use ac,it buzzes...its very good with 9v battery.

[Jdansti]

Glad you got it going!  You might need a quieter power supply. Here are a couple of good inexpensive ones:

1Spot:
http://www.visualsound.net/index.php/products/pedal_power_supplies/1_spot_power_supply/

Danelectro DA-1: http://www.danelectro.com/more_da1.html

[jogina111]

is there a diy adapter as quite as those?

[artifus]

search for psu or power supply and you'll find plenty. ^

this may help: http://www.beavisaudio.com/Projects/Huminator/

*also* http://www.muzique.com/lab/filter.htm

[deadastronaut]

@john, not sure, i just like overall volume on the end.


would a higher value cap to ground help jogina out...say 220uf...470uf...just guessing though..

@jogina:  at least its working properly on a battery now..good.

[jogina111]

470uf >>>lug 3 of pot.....lug 2 of
pot to output.....lug 1 to
ground?  would this arrangement  lessen the distortion of the amp? i wan my amp to get to a low volume but still have full distortion on.

[Jdansti]

This shouldn't reduce the distortion generated by the pedal.  I guess that if you are also trying to generate distortion by using the pedal to overdrive the amp, then turning the volume pot "down" on the pedal would lessen this overdrive. Turning the pedal's volume pot all of the way "up" should give you the same volume as no pot.

[jogina111]

but its no pedal...its a built in drive in the amp..

[Jdansti]

Right!  Sorry, my bad! 

[jogina111]

I tried rectifying thd ac to amp connection but its no good.. Amp still humming and rectifyer cap gets too hot.

[Jdansti]

Hmmm.  Can you post a drawing of what you're doing or else a photo?

[jogina111]

photos-a.ak.fbcdn.net/hphotos-ak-ash4/251522_464004213633903_917833184_a.jpg

[Jdansti]

Sorry, but I can't access your photos.  Maybe part of the URL is missing.

If you are going to do much posting on the forum, you might want to register with PhotoBucket and upload your photos there. After you upload them, copy the "Direct Link" in PhotoBucket, press the "Image" button at the top of the "Post Reply" window in the forum, and paste it between the two [img] designations that appear in your text.

[jogina111]

something like this after the wallwart

[Jdansti]

OK- just checking- what is the secondary voltage and what is the voltage rating of your caps?