Greetings all, apologies if this has been reiterated ad-nauseum but an initial search didn't reveal any results. I have a CKKIII that I built a couple years back and I've been experiencing troubles with a buzz from certain sources (in particular, sources that share a common ground). For instance, my iPhone does not cause this issue, particularly whenever its operating on battery, but if I plug it into my source on my desktop computer (an Audiotrak Prodigy Cube), I get a very loud hum, so I'm assuming the issue is related to the ground. I've installed AMB's recommended ground-loop breaker and this helped a little bit, but I still have the issues to a large extent. Does the ground-loop breaker just need to be modified a little bit, or what are some other steps I can go through to try and work all of this out? Thanks for your help.

with the amp unplugged, measure the resistance from the star ground to your case. If its less than the 10 ohm (or resistance used for your ground loop breaker) then the ground is connected through something else - inputs, output, pot, stand-off, etc.