i've been messing with a cheap ebay amp pcb. i'd rather not disclose the model for the fear of hurting the seller, and my construction is always less than perfect, so i don't want the blame shifted all to the product, but, this amp was suffering from an oscillation in one channel. (it's a stereo pcb) the channel farther away from the psu caps, as expected. the flaw shows up as a static noise in high frequency rich moments such as piano or... yeah, mostly just piano. 
i try everything i known until on a whim i just run my finger over the pcb, and to my surprise the noise goes away when my finger's over certain spot. so on a further whim i lay aluminium foil over where my finger was, and now the noise is gone.
what could've been the issue and how did this foil solve it?
one culprit that i can think of is my resistors being inductive.
i try everything i known until on a whim i just run my finger over the pcb, and to my surprise the noise goes away when my finger's over certain spot. so on a further whim i lay aluminium foil over where my finger was, and now the noise is gone.
what could've been the issue and how did this foil solve it?
one culprit that i can think of is my resistors being inductive.