My system is dual purpose (2 Chan and HT, with a Marantz receiver running bypass with my BHK Pre), with a P15 (only used for the 2 Chan audio components—HT stuff, including receiver, is hooked up to a separate Panamax unit).
About two months ago, I replaced my equipment rack, and the delivery guys/installers were kind enough to stick around and reposition/reconnect all my components.
After they finished the re-install, they guys mentioned a pretty pronounced hum/hiss through the speakers, with the right speaker significantly louder. I figured maybe it was just a positioning issue with the gear (or more likely the cables) and that I would fix it later. On most days thereafter, the noise wasn’t noticeable from the listening position; other days it was really noticeable (like in the next room over noticeable), mostly (but not always) when utilizing HT.
So, fast forward to yesterday, when I finally got around to looking into it—disconnected everything and starting adding back in. Dead quiet with just the amps, but once either the DS DAC or the Pre entered the chain, the noise came back.
After scratching my head for a bit, and running out to Record Store Day, I rolled in different tubes to the amps and the pre. Still no joy.
I was about to call it a day when I noticed two things on the P15 that were different than pre-install:
Marantz was plugged into the P15 (same HC zone as the right amp); and
VPI ADS was plugged into the same zone as the BHK Pre (I used to have it in the same zone as my phono stage). Note, though, that the hum/hiss was there even with the ADS turned off.
First, switched the Marantz back over to the Panamax—the 60 Hz hum disappeared immediately.
Second, switched the ADS back into the same zone as the phono stage—the rest of the noise (more of a hiss than a hum) disappeared—not completely, but only with ears up to the speakers—and right channel not more pronounced than left).
I’m now really perplexed about why the noise happened and why the “fix” worked. It’s just too weird.
I’m only the fence whether the “fix” was more correlation than causation—i.e., maybe in switching the cable position on the P15, I repositioned them ever so slightly in relation to other cables, other components, the wall, etc.