Power Question

toesalad

toesalad

Inspired
I have an Orange Crush 35RT with an effects loop. When I run my FM9 into the return of the effects loop, there is an annoying hum that I hear if both the FM9 and the Orange are plugged into the same outlet. When I plug them into different outlets, everything is dead silent.

Is this the kind of problem a power conditioner would solve? Or is there something else I can buy that would allow me to isolate multiple devices on the same outlet?
 
@toesalad,
You've likely already solved your problem by identifying it. There's likely a ground loop using the same circuit; unless your Orange has a ground lift switch in back, or check the back of your FM9 next to Output 3 (there's a ground lift switch there) you might need to power your FM9 and Orange on separate outlets (read: separate circuits).
 
It can depend on the outlets. Here in the US, houses are fed with 240 volts that are split into two out of phase 120 volt rails in the fuse panel. Every other 120V breaker is fed by the opposing rails, so you end up with some outlets on one rail and some outlets on the other and they can be better isolated from each other on the hot side.
 
mr_fender said:
It can depend on the outlets. Here in the US, houses are fed with 240 volts that are split into two out of phase 120 volt rails in the fuse panel. Every other 120V breaker is fed by the opposing rails, so you end up with some outlets on one rail and some outlets on the other and they can be better isolated from each other on the hot side.
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But if they're on the same circuit then they're in phase. If they were on separate circuits, especially coming from different rooms, then there'd be a larger chance of a ground loop, right?
 
This is another box that may help (and is passive)... Not sure it's for your "case," but I have an earlier model and was just re-reading the manual today (never used it so far, but seems quality stuff).
Lehle P-Split III
"Another useful application for the LEHLE P-SPLIT III is as a hum suppressor. Frequently background noise caused by ground loops occurs when two electronic devices are connected to each other. The LEHLE P-SPLIT III provides a simple, but extremely effective remedy when installed between the two units. Using the ISO output, the devices are galvanically isolated and background noise becomes a thing of the past."
 
mr_fender said:
It can depend on the outlets. Here in the US, houses are fed with 240 volts that are split into two out of phase 120 volt rails in the fuse panel. Every other 120V breaker is fed by the opposing rails, so you end up with some outlets on one rail and some outlets on the other and they can be better isolated from each other on the hot side.
Click to expand...
Depending on his location and age of his house may be a significant factor. If the previous owner didn't wire his house circuits correctly, there is likely significant ground loops issues. Yet the OP said plugging his FM9 and Orange into 2 separate outlets produced no hum.

If the FM9 ground lift switch doesn't solve his problem, it if were me, I'd simply invest in a Furman 6 to 8 outlet surge protector and plug the FM9 and Orange into that. About $38 to $40 Sweetwater or amazon.
 
Greg Ferguson said:
But if they're on the same circuit then they're in phase. If they were on separate circuits, especially coming from different rooms, then there'd be a larger chance of a ground loop, right?
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Depends on the source of the hum. If there's equal ground hum from out of phase outlets, they could cancel out the noise like a humbucker.

The ground loop can also exist post outlet between devices. In that case the choice of outlet doesn't make much difference. For that you need to lift the ground or isolate one of the devices with something like a Hum-X or power conditioner with isolated outlets.

Keep in mind too with effects loops and 4CM, you have multiple ground connections between inputs and outputs of the two devices. That can often make the issue even worse. Ideally, we'd have balanced I/O between all connections in something like 4CM, but that is pretty much never the case. With unbalanced connections, the cable shield is the return path for the audio signal, so you can't lift one side of it the way you can with balanced connections. That's why you'll see ground lift switches on XLR outs and not unbalanced 1/4" ones.
 
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One other thing to consider, is the outlet wired correctly? When troubleshooting hum I always start with a given and if the outlet is wired incorrectly you will be chasing your tail or buying equipment you may not need.

I carry one of these little $10 guys in my gig bag in the event there is questionable power or hum problem.

power-gear-voltage-tester-50542-64_100.jpeg
 
Thanks everyone for the helpful replies so far, this discussion has been really informative.

Sixstring said:
I carry one of these little $10 guys in my gig bag in the event there is questionable power or hum problem.

View attachment 109483
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I have started out by following this suggestion here and ordering one of these on Amazon. I live in a Montreal apartment that has a single breaker box in the basement suite - so likely converted from what was once a large townhouse. I know some of the plugs are ungrounded, probably because it was never originally wired that way. Hopefully this device will give me a better picture of the wiring situation.

I will report back when I learn more.
 
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