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.
It's almost impossible to tell without seeing the PCB or schematic, but when a circuit is this sensitive to a nearby finger it's usually a construction or design flaw. Ground loops can cause oscillation, but if foil stops the oscillation then your problem is probably with FETs oscillating or the stability compensation needs fixed.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.