[Zemo]

Hey guys, I put together a mint, and it's not working right.... it sounds fine, but when it's outside of the case, I get various squelching RF-type noises at different pot positions, wich happen to change as I get close to the amp..... I cased it up, to get rid of the outside interference, and I still hear an RF-type noise at 11:50-ish. The position that generates RF noise changes when I plug in a source.

I've already replaced the pot and reflowed all of the joints. I also looked at this thread wich a person had a similar problem: http://www5.head-fi.org/forums/showt...threadid=60219

I don't have a DMM right now, so I couldn't tell you the DC offset or anything...hopefully I'll be getting one tomarrow.

Components used-
- AD8620
- 2stacked buf634u
- 680uf 10V caps
- Vishay Dale 1% resistors
R1 - 1k
R2 - 470k
R3 - 1k
R4 - 10k
R5 - 1.5k
R6 - 470k
R7 - 100k
R8 - jumpered
R11 - 100
-Pana EVJ pot
-reccomended D1 and D2

Any ideas?

 

[till]

Are there any long wires in your design? E.g., hookup wires for plugs and the power LED? I found that my amps are more likely to pick up RF if I use too many or too long wires.
HTH

 

[Zemo]

nothing longer that about 3"....it's inside of a mint tin shouldn't the tin be adequately shielding it?

 

[tangent]

This could be a grounding problem.

Also, did you test before you stacked the buffers?

 

[fiddler]

hm, nm

 

[Zemo]

no, i didn't check it before I stacked the buffers....

also, what could be not grounding properly? I'll check all of the ground connections...

 

[meat01]

Check that you don't have the following:

-solder bridge
-wire touching ground that should not be
-wire not touching ground that should be
-2 wires touching each other that shouldn't be.

 

[tangent]

The best way to check your grounding is to pick one ground point, hook your meter probe to it, and then measure resistance from there to every other point in the circuit that should be grounded. You should also check resistance against the power rails, which should be very high.