Chip Amp buzzing problem

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Hey all, just got done building my first chip amp and it works great, except for one thing- it buzzes/hums incessantly. I have jury-rigged a power supply with small alligator clips to an old AC adapter until I can go to radioshack to get a proper setup. Is the buzz/hum a product of this rig, or is it something else, such as a bad connection somewhere or a grounding issue? I have checked the pcb and all of the components seem to be properly soldered without any bridging between leads. And yes, the adapter's output is withing the correct operating range for the amp. Thanks for the help.
 
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Heres the schematic, its a pretty simple design. I tried grounding the input, heatsink, and the power supply as you suggested and it decreased the noise somewhat. However the noise is still noticeable with all of them grounded. I might try the star grounding method if you think its worth a shot. Thanks once again!
 

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then ... if that is the case ... i will suggest to look at and try to improve on the power supply section first ... if you really want low noise supply ... then try to increase the capacitance ... maybe to about 22000uF and see if it does improve matters or not

Another thing, C12 should be located nearby (but not touching) with the IC chip amp ... did u did that?

And it might be helpful if you can take a picture of your amp and i can see what i can help you on this matter ...
 
Thats an interesting point, C12 is separated from the chip by the largest cap on the board. Is this part of my problem?

Most probably .... most chip amps really require a 0.047uF and 0.1uF small capacitor to prevent oscillation ... if there is no hole on the PCB board for that, then i would suggest try locate the GND and Vcc pin from the bottom of the board (nearby the IC) then solder a ceramic capacitor 0.1uF and see what will happen..
 
C12 will prevent the schip from oscillating, best is to solder it right on the IC pins, keep the lead as short as possible. The advice of dannyjmf is absolute proper.
C11 filters radio signals pickt up by the wires going into the amp, allso should be as close to the IC as possible. A larger value will supress the radio signals even more, but will limit the freqvency range of Your amplifier. (will lower the freqvency of the highest sound it will recieve for amplifying). 220 pF is a quite safe value, it won't be noticeable, but will keep things clear.

Maybe a few pictures of the actual board, and the powersupply would be more helpfull.
Along with the exact wireing schematic.
 
Alright, just got done with some more soldering and testing. Replacing the C11 with a higher rated capacitor greatly reduced the frequency of the noise, thanks for that suggestion. As for relocating C12 to the pins of the IC, there was no decrease in frequency or amplitude. I also (somewhat) fixed the power supply, its now soldered directly to the board. There still seems to be some sort of grounding problem, when I touch either the heat sink or the electrical ground wire, the buzzing becomes inaudible. I also tried the amp in several different rooms, so I don't think there is a problem with the outlet I was using. Once again, thanks for the help!
 
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