I've seen a lot of question recently on how to solve ground loop noise problems. In a majority of cases I've seen, these have involved powered speakers (either mains or subs) being connected with unbalanced connections. I've thought a little about why in 40 years of owning audio kit, I've never had a problem:
Back in the day a "HIFI" was typically a stack of Amp, Tape Dec, Tuner, CD player etc perhaps with a turntable on top. Everything was connected with short RCA leads and everything was plugged into the same power socket. The only part of the system that was remote would be passive speakers - which being passive have no ground reference. Unbalanced connections were fine in these typical consumer applications, with very little scope for creating a problematic ground loop.
Things have changed - more and more often people are incorporating powered speakers and powered subs into the mix. These are often placed around the room (especially subs) and may be connected to separate power sockets. Even when the power leads are run back to the same power strip, we are still left with a significant ground loop from the preamp (whatever form that takes) via RCA to the speakers then back to a common earth via the power cord. Worse - speakers normally have significant separation from each other, so each one creates a separate ground loop.
Add to that a noisy PC with powerfull energy chomping graphics card and you've a recipe for stray magnetic fields getting into a loop and causing ground noise - even if there is no PC, mains wiring run <1mm from the earth wire can easily induce mains hum into the loop. There are a plethora of other devices that can also get in on the act.
I think the message is - if you are planning to use powered speakers of whatever kind, plan also to use fully balanced (or some other form of noise rejecting connection - eg toslink) interconnect to them.
And if you use a PC as source which is ground referenced - plan to use an optical connection from that to your DAC - or at least have the option to fall back to that if you have issues.
Back in the day a "HIFI" was typically a stack of Amp, Tape Dec, Tuner, CD player etc perhaps with a turntable on top. Everything was connected with short RCA leads and everything was plugged into the same power socket. The only part of the system that was remote would be passive speakers - which being passive have no ground reference. Unbalanced connections were fine in these typical consumer applications, with very little scope for creating a problematic ground loop.
Things have changed - more and more often people are incorporating powered speakers and powered subs into the mix. These are often placed around the room (especially subs) and may be connected to separate power sockets. Even when the power leads are run back to the same power strip, we are still left with a significant ground loop from the preamp (whatever form that takes) via RCA to the speakers then back to a common earth via the power cord. Worse - speakers normally have significant separation from each other, so each one creates a separate ground loop.
Add to that a noisy PC with powerfull energy chomping graphics card and you've a recipe for stray magnetic fields getting into a loop and causing ground noise - even if there is no PC, mains wiring run <1mm from the earth wire can easily induce mains hum into the loop. There are a plethora of other devices that can also get in on the act.
I think the message is - if you are planning to use powered speakers of whatever kind, plan also to use fully balanced (or some other form of noise rejecting connection - eg toslink) interconnect to them.
And if you use a PC as source which is ground referenced - plan to use an optical connection from that to your DAC - or at least have the option to fall back to that if you have issues.
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