Here's a question for people with a similar system set-up to me. I have my Foreplay preamp in the corner of the room with most of my audio sources and ParaSEX power monoblocks next to each speaker. While this means only a metre or so of speaker cable (more inside the cabinet following the horn than out of it) I have 10 metre pre to power amp cables. Unfortunately, the power amps are on a different mains outlet to everything else, giving the perfect ingredients for a HUM LOOP.
The solution I am using at present means the safety (mains power) ground at each power amp is disconnected. (I use a switch inside the amp in the mains ground line.) While this gives a fault current path back to the ground bus of the preamp which will be sufficient to trip my earth leakage circuit breaker, I am concerned the (relatively) high impedance of the signal cable will result in a lower fault current with the possibility of significant reduction in the trip speed of any mains safety devices.
For my next power amp project, I am considering reinstating the safety ground at the power amps for the chassis and separating off the signal ground for the audio, linking with a resistor. This should allow the audio to be referenced to ground but give the lowest audio ground impedance through the audio interconnect rather than the house wiring. I have seen a number of circuits for various purposes using this method but I have seen resistors between 330 and 10K ohms. Is there anyone out there using this method with Bottlehead gear and what value of resistor works for you?
John
Amateur Audiophile and Backstreet Boffin.
Original Foreplay with C4S + Sweet Whispers
ParaSEX amps with MQ nickel-cored outputs
Factory-built Lowther Acousta 115s with silver-coiled DX3s, wired in DNM solid-core
KEF active sub (help for the last couple of octaves).
Bottlehead DAC on batteries.