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removing noise between Korg Triton and Universal Audio pre

Discussion in 'Recording' started by oldtimefiddler, Sep 11, 2007.

  1. Gents,

    In our new studio we've a Triton workstation on a back console pluged into a clean isolated/grounded power source.

    From the left/right Main output on the Triton we've connected it to a 2 channel Universal Audio 2-610 Tube Preamp which sets at the front console, powered by a totally separate clean isolated/grounded circuit.

    Hit record on Pro Tools and there's a bunch of noise on both those channels.

    Now, unplug the Triton and plug it into the same power source as the pre amp, and it's all clean. OR, take a 2 prong ground lifter and the problem is gone also, on the previous power source.

    I tried connecting the grounds from both sources together, and still have noise.

    I'm pulling my hair out.

    Thanks for any help guys,
    oldtimefiddler
     
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    What kind of "noise"? A 60-cycle hum? What you are describing sounds like a "ground loop" to me. Something isn't properly grounded. Who wired your "new studio"? There should be a common "ground plane" for all of your audio gear power, not "totally seperate".
     
  3. Link555

    Link555 Well-Known Member

    Yes I agree with Moonbaby, sounds like you have created ground loop with your isolated circuits. There must a impedance across the 2 isolated grounds.
     
  4. RemyRAD

    RemyRAD Well-Known Member

    The devices you are using are all low current devices. I.e., they are not power hogs. And so, you are creating the world's worst ground loop by plugging in grounded equipment into different isolated grounded outlets.

    This don't work as you have discovered. Grounding is one thing but ground looping doesn't work for audio. Proper grounding for both studios and broadcast facilities goes well beyond the beginner discussions here. I am assuming this is a basement and/or bedroom studio?

    So, my recommendation is simple. Plug everything into the same electrical outlet and outlets strips, as long as it does not exceed 20 amps. Preferably no more than 15 amps. If you still detect a hum, start by lifting the ground electrically from each piece of equipment with a "cheater plug" (3 into 2) electrical plug. You will eventually find the piece of equipment that is causing you the ground hum grief. But beware. One must be careful as poor or shoddy repair and maintenance could cause a hot chassis on a piece of equipment. So if you have a simple voltmeter, set it to the AC voltage setting and connect between chassis. Small voltage differentials are to be expected. But if you see 60 to 120? STOP! YOU HAVE A HOT CHASSIS. Now that is a grounding problem that must be dealt with. Chances are, you won't see that scenario with the equipment that you have just described as there are no high-voltage circuits within? That situation frequently occurs with tube equipment, such as guitar amplifiers and PA systems.

    Conversely, the grounds can be lifted from pin 1 of a 3 pin balanced XLR that is plugged into a console or mixer. In that respect, because the signal is actually carried on pins 2 & 3, the shield is only necessary and should be connected at the source of the feed. In that way, the electrical ground on the equipment can remain grounded. The same also holds true for unbalanced equipment but not quite in the same way and should be avoided. When connecting unbalanced connections together, the grounds need to be connected together. And that's when you will hear ground loop problems requiring a lift of the ground on the electrical side, at the plug.

    Now if we want to get really tricky, we could talk about transformer isolated balance power distribution? Not tonight. I have a headache.

    Electrifying and beautiful.... Ouch!
    Ms. Remy Ann David
     
  5. Link555

    Link555 Well-Known Member

     
  6. RemyRAD,

    Thanks for your response. I'm the electrician that wired this place, an old garage with a half mil$ thrown into the remodel, and about the same amount in equipment. I'm a state licensed electrical contractor/Master electrician.
    All the grounds from the circuits join together on a common ground bar in the panel, isolated from the neutral bar. It's a sub panel--the main disconnect being outside--hence the separation of the neutral and ground bars.

    The equipment that's causing the stereo level monitor in Pro tools to jump , and creating the noise coming from the monitors, is on opposite sides of the control room.

    The majority of the wiring in the studios is done with Romex, as opposed to conduit or flex.

    Does this help to diagnose this conundrum?

    Thanks so much!!

    Peace,
    oldtimefiddler

    The devices you are using are all low current devices. I.e., they are not power hogs. And so, you are creating the world's worst ground loop by plugging in grounded equipment into different isolated grounded outlets.

    This don't work as you have discovered. Grounding is one thing but ground looping doesn't work for audio. Proper grounding for both studios and broadcast facilities goes well beyond the beginner discussions here. I am assuming this is a basement and/or bedroom studio?

    So, my recommendation is simple. Plug everything into the same electrical outlet and outlets strips, as long as it does not exceed 20 amps. Preferably no more than 15 amps. If you still detect a hum, start by lifting the ground electrically from each piece of equipment with a "cheater plug" (3 into 2) electrical plug. You will eventually find the piece of equipment that is causing you the ground hum grief. But beware. One must be careful as poor or shoddy repair and maintenance could cause a hot chassis on a piece of equipment. So if you have a simple voltmeter, set it to the AC voltage setting and connect between chassis. Small voltage differentials are to be expected. But if you see 60 to 120? STOP! YOU HAVE A HOT CHASSIS. Now that is a grounding problem that must be dealt with. Chances are, you won't see that scenario with the equipment that you have just described as there are no high-voltage circuits within? That situation frequently occurs with tube equipment, such as guitar amplifiers and PA systems.

    Conversely, the grounds can be lifted from pin 1 of a 3 pin balanced XLR that is plugged into a console or mixer. In that respect, because the signal is actually carried on pins 2 & 3, the shield is only necessary and should be connected at the source of the feed. In that way, the electrical ground on the equipment can remain grounded. The same also holds true for unbalanced equipment but not quite in the same way and should be avoided. When connecting unbalanced connections together, the grounds need to be connected together. And that's when you will hear ground loop problems requiring a lift of the ground on the electrical side, at the plug.

    Now if we want to get really tricky, we could talk about transformer isolated balance power distribution? Not tonight. I have a headache.

    Electrifying and beautiful.... Ouch!
    Ms. Remy Ann David[/quote]
     

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