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Author Topic: Balanced Power Questions  (Read 9517 times)

Mike Sokol

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Re: Balanced Power Questions
« Reply #20 on: November 25, 2013, 05:51:35 pm »

Just out of curiosity I looked up one of the Furman units mentioned... $2500, 3 rack units, and 90 lbs for 20 amps of balanced power. On the bright side there's a convenient front mounted USB charger so you can charger your phone with it.  ;D
Yup, we've got two of them in the machine closet. One for the SSL and the other for studio outlet power. Looks impressive, but I'm not buying into the cost/benefits factor.

JMS
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Jerome Malsack

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Re: Balanced Power Questions
« Reply #21 on: November 25, 2013, 07:49:55 pm »

So basicly we are to a decision that balanced power offers no advantage. 

An isolation transformer can provide just as much protection from noise. 

If we go on Large Ships like Navy or Cruise ships we might want to verify if we are on balanced power to ensure we take appropriate protections.
Ocean going vessels may have balanced power by design.  Turning off the power switch will not shut off the power on the second leg and leave 60 volts running. 

http://www.norfolkwire.com/default.aspx?page=item%20detail&itemcode=BROPOW+Z6-62P

 
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Mike Sokol

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Re: Balanced Power Questions
« Reply #22 on: November 25, 2013, 08:45:36 pm »

So basically we are to a decision that balanced power offers no advantage.
Yes, I would say that's a fair statement according to the wisdom of the swarm/collective/gaggle.

Quote
An isolation transformer can provide just as much protection from noise. 
That's a secondary question that's not really been discussed on this thread. But yes, from my own experience a properly placed and grounded power isolation transformer (with it's own G-N-E bond) will reduce a lot of noise from power lines. Now my experience was while measuring military grade component during manufacturing of nuclear missile guidance systems, so it may not translate to audio systems. But the theory and physics should be the same for both systems.

So have any of you used AC power isolation transformers with a secondary grounding system to solve a noise problem? If so, what were the details? 

Mike Sokol
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Mac Kerr

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Re: Balanced Power Questions
« Reply #23 on: November 25, 2013, 10:17:32 pm »

So have any of you used AC power isolation transformers with a secondary grounding system to solve a noise problem? If so, what were the details? 

AFAIK every AC isolation transformer I've used passes through the ground. They have all taken 3 4W (G-X-Y-Z)) on the line side and put out 3 5W (G-N-X-Y-Z) on the load side. I find that with newer equipment AC isolation is more work than worth, but they keep showing up on the truck.

Mac
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John Roberts {JR}

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Re: Balanced Power Questions
« Reply #24 on: November 25, 2013, 10:27:14 pm »

Just to be accurate there are multiple vectors for mains noise signal corruption.  This symmetrical power while IMO impractical (for safety/compatibility reasons), really does have a scientific basis for potentially reducing some types of noise. Instead of 120V signals all around, the dual 60v is 1/2 the peak voltage to begin with. The outside world is not looking at the two mains leads differentially. To the outside world it does look like less voltage. In theory this means less noise picked up by nearby signal conductors. Besides 6 dB smaller mains voltage waveforms the two symmetrical waveforms will possibly cancel out. Visualize one leg pushing noise while the opposite leg is pulling an exactly opposite version of that noise.

6dB+ less noise is not inconsequential if hum is the dominant noise in your studio, while good practice using well shielded (balanced) wiring will generally make hum a non-issue (with modern well designed gear).

So IMO not a pure marketing invention. More like a well intentioned, if not slightly desperate, attempt to deliver a quieter working environment in simpler times. 
 
JR

PS: WRT isolation transformers, all transformers are bandpass filters so very HF noise on mains can get filtered out by an isolation transformer. FWIW the products normal transformer will act like a filter too.
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Re: Balanced Power Questions
« Reply #24 on: November 25, 2013, 10:27:14 pm »


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