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Building electrical problems - halp!


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I'm looking for some help with what I think is a building electrical issue.

Just picked up a pair of SR-002s from Justin. I've noticed an annoying hum in the right channel whenever I listen at my desk, but not when I listen in the bedroom (i.e. it's not the headphones). The hum is loudest when the SR-002 is connected to my gamma2 -> Mac (doesn't matter if the Mac is plugged in or not), but it doesn't go away when I disconnect the SR-002 amp from the gamma2, or even when I disconnect the SR-002 headphone cable from the amp. As in, I can hear a fricking hum even when I'm wearing headphones plugged into nothing at all. I've never heard this hum with my other Stax but I guess the SR-002s are uber-sensitive to this problem.

Two things make the hum go away: if I touch the metal surface of my dac/amp/computer, or if I unplug every electrical object near my desk. My building is from the 1950s and although I have a three-prong outlet it is not grounded.

Would it be correct to assume that somehow the SR-002 cable is picking up a stray electrical field, to further assume that this field is emanating from my dac/amp/computer, and that by touching these objects I somehow 'correct' whatever electrical failure causes this field? I am no electrical engineer, so these are just guesses. More importantly, is there some magic doo-dad that I can buy to fix this issue?

Merci,

Sameer

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[dusty]Maybe it doesn't know the words.[/dusty]

 

No, seriously, it sounds like a ground loop (look up ground loop -- it's a common problem with common solutions).

 

Well, to start with, buy one of these, and see if it's a simple miswired power outlet:

 

51J-Kye8q6L._SL500_AA300_.jpg

 

Available at most hardware stores and larger department stores (Lowe's Home Depot Target etc.)

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You can hear hum with the headphones on your head, but them not being plugged into anything? And this hum is coming thru the headphones?

 

I'm looking for some help with what I think is a building electrical issue.

Just picked up a pair of SR-002s from Justin. I've noticed an annoying hum in the right channel whenever I listen at my desk, but not when I listen in the bedroom (i.e. it's not the headphones). The hum is loudest when the SR-002 is connected to my gamma2 -> Mac (doesn't matter if the Mac is plugged in or not), but it doesn't go away when I disconnect the SR-002 amp from the gamma2, or even when I disconnect the SR-002 headphone cable from the amp. As in, I can hear a fricking hum even when I'm wearing headphones plugged into nothing at all. I've never heard this hum with my other Stax but I guess the SR-002s are uber-sensitive to this problem.

Two things make the hum go away: if I touch the metal surface of my dac/amp/computer, or if I unplug every electrical object near my desk. My building is from the 1950s and although I have a three-prong outlet it is not grounded.

Would it be correct to assume that somehow the SR-002 cable is picking up a stray electrical field, to further assume that this field is emanating from my dac/amp/computer, and that by touching these objects I somehow 'correct' whatever electrical failure causes this field? I am no electrical engineer, so these are just guesses. More importantly, is there some magic doo-dad that I can buy to fix this issue?

Merci,
Sameer

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It's certainly a grounding issue or something is radiating an awful amount so the headphones are picking it up.  If you have something earthed then run wires to that and see if it fixes the issue. 

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You can hear hum with the headphones on your head, but them not being plugged into anything? And this hum is coming thru the headphones?

Yea and yea. I turn my head, the hum turns with me. I take the SR-002s out of my ear, I don't hear a hum. All with the cable not being plugged into anything. 

 

It's certainly a grounding issue or something is radiating an awful amount so the headphones are picking it up.  If you have something earthed then run wires to that and see if it fixes the issue.

I checked my wall receptacle with a DMM - as far as I can tell the ground pin on the jack is not connected to anything at all.

I think something is radiating - I do have three 120V-100V stepdowns (one of which is switching) that might be causing the problem. Sadly the nearest earth is two rooms away, although I may have to bite the bullet and run a long extension cord throughout the house.

Edited by oogabooga
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At least try it in the other room with the earthed/grounded plug first, to see if that even fixes the problem.  You don't necessarily need to run all the wires all the way, just the ground.  And if you can find something else grounded that's closer (like plumbing in the walls), you can run the ground wire from that.

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  • 2 months later...

I have an older house, built in 1948. I upgraded the outlets after an electrician friend pointed out most of cable runs were actually already grounded, to the outlet box, not to the outlet; ie the cable was in a metal housing, and that was secured to the outlet box. All I had to do to ground the outlet was run a short wire from the ground screw on the outlet (usually a green screw, on the ones I bought at Home Depot) to the screw that held the outlet in. Which extended the ground from the outlet box to the outlet.

 

Of course you need access to the circuit breakers, and to map out your circuits first, for which that tool Dusty Chalk pictured is really useful. I don't know if the metal housed-cabling was common practice or not. There's a word for it I don't remember. I've never had an issue with a grounding hum, but I did have some random noise coming through my desktop amp and out some speakers; that I think had something to do with the computer power supply though, because grounding experiments didn't affect it, but running the amp off a battery fixed it.

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  • 3 years later...

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