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ground hum in studio a/c
Old 24th August 2007
  #1
Gear Nut
 

ground hum in studio a/c

I'm not sure if this is the correct forum for this inquery,... but , I have a ground hum in my one room studio here at my house. Over the last year or so I've really cleaned up my signal chain, particularly by adding Benchmark conversion. Perhaps it's always been there, but I now have a hum that's driving me crazy.

I use an older pair of active, Tannoy PBM 8's for monitoring. The hum isn't loud at all, ... just loud enough to annoy me, and probably get in the way of certain frequencys.

I've eliminated everything in my rack, as I've simply unplugged everything in the room, and then plugged both speakers ( on at a time ) into an a/c outlet, by themselves without an input signal, and can still hear the same hum.

I also notice that an acoustic amp I have in the room has the same hum.

At this point I would assume the power to my house, or room isn't up to snuff, so to speak. Not being an electriction I'm at a loss as to what to do.

Would a more expensive power supply/conditioner alleviate the hum? I use a Trip Lite "iso bar" currently.

Thanks,
Marc
Old 24th August 2007
  #2
Gear Maniac
 
Trancetones's Avatar
 

The $30 20 minute fix. Go to home depot and get a run of 12 gauge green wire, a pair of wire strippers and a pipe ground. Attach the pipe ground to the cold water pipe in your basement that comes from the street. Attach the wire to the pipe ground and run it into your studio. Turn off the circuit breaker and open the outlet(s) and remove the ground that is there and replace it with the wire from the basement. Turn on the circuit breaker. Done and done.
Old 24th August 2007
  #3
Lives for gear
 
Disjointed's Avatar
 

although that might solve the grounding problem.. it is a solution no longer allowed by electrical code... the main problem being that most water lines - now-a-days are plastic, or there is a plastic coupler somewhere along the way that breaks the electric ground.... .. even if you get a ground, it might be weak...
this is all well and good until you have a critical grounding problem, for some reason- then what happens is the way to ground for your electricity is through any faucet in your house and you!

your best bet it to drive an actual ground rod (theyre pretty cheap) in your basement 10' deep or so ... then use the grounding techniques as above.... consider using braided wire as well, the larger surface area is better at 'grabbing' and grounding RFI


gl
Old 24th August 2007
  #4
Lives for Jesus
 
stevep's Avatar
Do a search for " Star Ground " of coarse there is also RF which is another story but can be overcome




.
Old 24th August 2007
  #5
Lives for gear
 
nosebleedaudio's Avatar
 

Quote:
Originally Posted by Trancetones View Post
The $30 20 minute fix. Go to home depot and get a run of 12 gauge green wire, a pair of wire strippers and a pipe ground. Attach the pipe ground to the cold water pipe in your basement that comes from the street. Attach the wire to the pipe ground and run it into your studio. Turn off the circuit breaker and open the outlet(s) and remove the ground that is there and replace it with the wire from the basement. Turn on the circuit breaker. Done and done.
If you choose this suggesion make sure you connect it to the main AC ground, a floating ground is dangerous and NOT to code.
I would start with a dedicated circuit for your audio.
Old 27th August 2007
  #6
Gear Maniac
 
Trancetones's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
If you choose this suggesion make sure you connect it to the main AC ground, a floating ground is dangerous and NOT to code.
I would start with a dedicated circuit for your audio.

If the cold water pipe from the street is actually grounded (which it almost always is), then this is not a floating ground, this is a ground. The problem he is having IS the main AC ground that has other appliances on that are sending power down that ground causing the noise and he needs to get off that ground.

"although that might solve the grounding problem.. it is a solution no longer allowed by electrical code... the main problem being that most water lines - now-a-days are plastic, or there is a plastic coupler somewhere along the way that breaks the electric ground.... .. even if you get a ground, it might be weak...
this is all well and good until you have a critical grounding problem, for some reason- then what happens is the way to ground for your electricity is through any faucet in your house and you!"

Yes, if the pipe running from the street to your house is plastic, then you definetly will not get a ground from it. Nothing is 100% certain, but if is metal coming from the street then you will probably get a sufficient ground from it, in fact you will probably get a multiple mile ground from it.

"your best bet it to drive an actual ground rod (theyre pretty cheap) in your basement 10' deep or so ... then use the grounding techniques as above.... consider using braided wire as well, the larger surface area is better at 'grabbing' and grounding RFI"

This is true, but if you can't do that then the cold water pipe works fine as it is probably grounded. If you are running multiple outlets, then you should run multiple wires to that ground rather than daisey chain (star). If two pieces of audio equipment are plugged into different power outlets, there will often be a difference in their respective ground potentials. If a signal is passed from one to the other via an audio connection with the ground wire intact, this potential difference causes a spurious current to flow through the cables causing a hum.
Old 27th August 2007
  #7
Lives for gear
 
nosebleedaudio's Avatar
 

Quote:
Originally Posted by Trancetones View Post
If the cold water pipe from the street is actually grounded (which it almost always is), then this is not a floating ground, this is a ground. The problem he is having IS the main AC ground that has other appliances on that are sending power down that ground causing the noise and he needs to get off that ground.

"although that might solve the grounding problem.. it is a solution no longer allowed by electrical code... the main problem being that most water lines - now-a-days are plastic, or there is a plastic coupler somewhere along the way that breaks the electric ground.... .. even if you get a ground, it might be weak...
this is all well and good until you have a critical grounding problem, for some reason- then what happens is the way to ground for your electricity is through any faucet in your house and you!"

Yes, if the pipe running from the street to your house is plastic, then you definetly will not get a ground from it. Nothing is 100% certain, but if is metal coming from the street then you will probably get a sufficient ground from it, in fact you will probably get a multiple mile ground from it.

"your best bet it to drive an actual ground rod (theyre pretty cheap) in your basement 10' deep or so ... then use the grounding techniques as above.... consider using braided wire as well, the larger surface area is better at 'grabbing' and grounding RFI"

This is true, but if you can't do that then the cold water pipe works fine as it is probably grounded. If you are running multiple outlets, then you should run multiple wires to that ground rather than daisey chain (star). If two pieces of audio equipment are plugged into different power outlets, there will often be a difference in their respective ground potentials. If a signal is passed from one to the other via an audio connection with the ground wire intact, this potential difference causes a spurious current to flow through the cables causing a hum.
If again you choose the above suggestion make sure it is bonded"connected" to the main AC ground......
If not it WILL NOT trip a breaker if you develop a short.....
You will not have the needed "Ground fault current path".
Will add that every studio I have wired from the ground up is clean and hum free, and all the AC plugs are grounded.
The last one I did that has balanced AC is even quieter and ALL grounds are connected, nothing is floating.
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