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DJ equipment setup in Japan apartment has a lot of feedback

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#1
HI all I'm in desparate need of some help/advice and someone recommended that I post in here.

I have setup all of my DJ equipment in my Japanese apartment but I am getting a lot of hum/noise from the power lines through the system which increases if I turn lights or other significant bits of electrical equipment on in the apartment.

I have a Formular Sound FF-4000 mixer (bought from the UK but configured for Japanese voltage).
2x Focal shape active monitor speakers (again from the UK but I've changed the voltage switch to 100-120v) (connected using the balanced outputs and XLR cables)
2x Technics SL1200 turntables bought in Japan.

All of the items are going through a grounded power block which is connected to a ground socket (I can only assume this is working I don't know for sure). I have tried connecting the ground to a pipe in the kitchen too (via another long ground cable) but this didn't do anything but my method here was likely flawed as I just stuck the cable in place as a test.

I tried disconnecting everything except the mixer and listened through the headphones and I still get the feedback (which increases as I turn things on in the apartment) so I think there is a fundemental issue I'm desparate to solve.

Any thoughts on what I can do/purchase/further checks to solve this issue as it's pretty bad!

UPDATE:
Also I've just tried plugging it all in to a different socket and all of the hum has gone so I'm guessing it means something on the other sockets is causing the issue (although I've turned everything off and it's still there).
 
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Blumlein 88

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#2
Okay for starters do you mean feedback. Like when a singer using a mike goes out over speakers and creates a squealing feedback loop.?

Or are you referring to hum and noise from the power lines?
 
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#3
Okay for starters do you mean feedback. Like when a singer using a mike goes out over speakers and creates a squealing feedback loop.?

Or are you referring to hum and noise from the power lines?
Hum and noise from the power lines. Will edit my post.

Also I've just tried plugging it all in to a different socket and all of the hum has gone so I'm guessing it means something on the other sockets is causing the issue (although I've turned everything off and it's still there).

This does kind of solve my problem the only thing is there is no ground connector on the socket that works. How much of an issue is this?
 
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#5
Could be a fridge or florescent lights.
I've tested unplugging the fridge and it didn't change it (I think that's on a different circuit) but I do think it's the lights as when I turn down the dimmer on them it hums too (I had this relvalation about an hour ago). I've tried turning the lights off but the hum still happens but I still think it's them as there is a light always on in the switch! I can't think what else it could be (except maybe the air conditioning). I'm guessing there is no way to fix this without some sort of electrician re-wiring things?
 

RayDunzl

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#6
Also I've just tried plugging it all in to a different socket and all of the hum has gone so I'm guessing it means something on the other sockets is causing the issue (although I've turned everything off and it's still there).

This does kind of solve my problem the only thing is there is no ground connector on the socket that works. How much of an issue is this?

How much issue? Could create a shock (electrocution) hazard.

---

A pair of parallel diodes in series with the Earth line from the outlet might cure your trouble and maintain safety. It "lifts" the ground, but only for the first volt or so of shock fault.

Here's a product that does that for you - Ebtech Hum-X

Some ASR discussions here: https://www.audiosciencereview.com/forum/index.php?search/150821/&q=hum-x&o=relevance
 
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Blumlein 88

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#7
This sounds like a ground loop. Lifting the ground socket often gets rid of the hum. That could be an unsafe condition depending upon the particulars. I'm not familiar with Japanese wiring codes so I'll let someone else address that.

Initially was all the gear powered from one socket or more than one socket?

If more than one socket then the ground pin was at different potentials between the sockets. It could also be some interference from another device on the same wiring circuit like fridge or lights. But this sounds like a classic ground loop.

If you can plug everything into the same socket using power strips or extension cords with multiple plugs it should stop ground loops as the ground pin is the same for all the gear and you'll get no ground loop current. Now this assumes all the gear doesn't overload the single socket. So again not knowing Japanese conditions make sure the total wattage isn't too much. If not then it should be safe.
 
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#8
This sounds like a ground loop. Lifting the ground socket often gets rid of the hum. That could be an unsafe condition depending upon the particulars. I'm not familiar with Japanese wiring codes so I'll let someone else address that.

Initially was all the gear powered from one socket or more than one socket?

If more than one socket then the ground pin was at different potentials between the sockets. It could also be some interference from another device on the same wiring circuit like fridge or lights. But this sounds like a classic ground loop.

If you can plug everything into the same socket using power strips or extension cords with multiple plugs it should stop ground loops as the ground pin is the same for all the gear and you'll get no ground loop current. Now this assumes all the gear doesn't overload the single socket. So again not knowing Japanese conditions make sure the total wattage isn't too much. If not then it should be safe.
It was all in one socket on a single power block.
 
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#9
How much issue? Could create a shock hazard.

---

A pair of parallel diodes in series with the Earth line from the outlet might cure your trouble and maintain safety. It "lifts" the ground, but only for the first volt or so of shock fault.

Here's a product that does that for you - Ebtech Hum-X

Some ASR discussions here: https://www.audiosciencereview.com/forum/index.php?search/150821/&q=hum-x&o=relevance
Thanks, just looking in to that now but the issue I have is that they can only be used for one piece of equipmentand not a power block.
 

RayDunzl

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#10
Thanks, just looking in to that now but the issue I have is that they can only be used for one piece of equipmentand not a power block.
It has a 600W rating, How many do you need?

If one, plug it into the wall and plug everything else (the power block) into it.
 

RayDunzl

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#11
Or build your own from a short length of extension cord (with properly sized diodes):

1548744631021.png


https://groups.google.com/forum/#!msg/alt.guitar.amps/CJyWD3GaHfg/V40Y6kgm6XkJ

Lovguitar wrote:

"OK, kiddies - pull up a chair.

The $90 Hum-X works *really* well. So well,
in fact, that most people think some heavy mojo
must be involved...but inside that slick little adaptor
is a very primitive (but clever) little circuit. In a
standard AC receptacle, you have three contacts -
hot, neutral, and ground. The hot and neutral lines
pass straight through the adaptor, although there's
a tap from the hot line (with a resistor) to power the
LED. The mojo is in the ground line, which has
a pair of 6A/1kV diodes between the wall ground
connection and the adaptor's output socket ground.
These diodes are connected in parallel, with
the anode on one diode connected to the cathode
on the other. (And vice versa, obviously.) The
pair of diodes has a 1K 1/2-W rsistor in parallel
with it; as far as I can see, this resistor serves
to produce a "correct" indication when an outlet
tester is plugged into the adaptor, since without
it, the outlet tester will give an "open ground"
indication."
 

Blumlein 88

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#12
It was all in one socket on a single power block.
Okay so the HumX or homemade double diode extension goes on the single plug of the power block that plugs into the wall. And you should be fine with no hum and it will be safe.
 
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#13
Thanks for all the help everyone. Going to order one of those HumX's as that looks like it will solve the issue.
 

restorer-john

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#14
Personally I think back to back diodes lifting a safety earth is bordering on insane.

The currents that flow in a live chassis fault condition will vaporize 6A diodes and nobody will know, leaving a lethal, powered up device.

With a proper safety earth, the main circuit breaker will trip (or the line fuse on the device) and the lack of power will tell you there's a problem.
 
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#15
Personally I think back to back diodes lifting a safety earth is bordering on insane.

The currents that flow in a live chassis fault condition will vaporize 6A diodes and nobody will know, leaving a lethal, powered up device.

With a proper safety earth, the main circuit breaker will trip (or the line fuse on the device) and the lack of power will tell you there's a problem.
My plan is to use the Hum X so I can then properly earth everything. I'm still getting a hum now (it's started creeping in again). Going to get a voltmeter and check my earth is properly grounded too (I have a sneaky suspicion that it might not be).
 
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#16
Just in case anyone is interested. I got my Hum X today and it's not fixed the issue or done anything at all so I guess it's back to the drawing board!
 

AnalogSteph

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#17
Your mixer says
MAINS INPUT 115 - 230VAC INTERNAL SELECTION
Note 115 V, not 100.

I would think it possible that the power supply is dropping out of regulation and the ungrounded outlet just happens to provide a slightly higher mains voltage, barely allowing the regulators to do their job. Given the voltage selection option, it may very well be a linear (transformer-based) supply. If regulator input voltage is too low, a more or less substantial amount of ripple will pass through.

I suggest you pick up a step-up transformer for (US) 115 V devices on Japanese 100 V. Given the small step-up ratio required for the autotransformer, it is likely to be quite small for its rated power, so don't be surprised.

Oh, and it never hurts to have a multimeter around.
 
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#18
Your mixer says
MAINS INPUT 115 - 230VAC INTERNAL SELECTION
Note 115 V, not 100.

I would think it possible that the power supply is dropping out of regulation and the ungrounded outlet just happens to provide a slightly higher mains voltage, barely allowing the regulators to do their job. Given the voltage selection option, it may very well be a linear (transformer-based) supply. If regulator input voltage is too low, a more or less substantial amount of ripple will pass through.

I suggest you pick up a step-up transformer for (US) 115 V devices on Japanese 100 V. Given the small step-up ratio required for the autotransformer, it is likely to be quite small for its rated power, so don't be surprised.

Oh, and it never hurts to have a multimeter around.
Thanks. I'll try to see if anyone I know has one I can borrow to see if it does the job.
 

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