Hello guys, sorry basically a beginner in DIY, but anyways here's the story: I just purchased an old amp, and there is a distracting hum on the left channel. I was told that this could be because the capacitors "dried out". Now this hum is present on my HD558 and 650 (but less so), however on my...

I have an old Channel Islands VHP-1 amp and when I measure its DC Offset it's very close to 0v, showing 0.0 mV on my multimeter. But when I change the volume, gain setting, or turn off the device the DC Offset can spike up to 30, 80, 175 mV respectively, then slowly make its way back down to 0mV...