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In Reply to: RE: Ground is ignored in a balanced system. posted by Ralph on April 19, 2021 at 14:56:58
When I build RCA Cables. I use a 2 wire cable for + and - connection. I keep the shield floating. (I have tried tying it to the - cable as well) -- Still I have problems with ground loops. My solution was to lift the grounds, and install a GFCI on the circuit for safety. I've got to say that I do have a very quiet backround doing this, and is safer with a circuit with ground plug and no GFCI.What is your recommended solution for using gear that does not have balanced connections? Also, will balanced connections ALWAYS solve Ground Loops?
I've found very few people that understand what a ground loop is and how to solve one. They're full of suggestions that don't work however.
Edits: 04/19/21Follow Ups:
Chassis and audio grounds must not be the same thing in a single-ended system.
You have to ground the chassis thru the power cord for safety reasons- that is where ground loops really start to show up.
If there is some isolation between the chassis and audio ground of the amp or preamp, then you won't get ground loops. A resistor might be all that's needed to sort this out. Older equipment of course solved this by not grounding the equipment at all.
Balanced connections in high end audio will not always be ground-loop free although they *should*. If AES48 is observed in the equipment there will be no ground loop problems even though all the chassis involved are grounded.
If you had to lift grounds to get rid of ground loops there is a design flaw with the grounding scheme of at least some of your equipment. BTW A GFCI won't give you much protection if the grounds have been lifted!
You should be able to just plug and play. But so much of high end audio is done by folks who don't have a full grasp of how stuff like this works. Grounding in particular is poorly understood.
You don't even need a Ground wire, much less a 3 Prong Plug for a GFCI to work. That's what a GFCI is for: this is per the NEC."A grounding-type receptacle that is GFCI protected without an equipment grounding conductor is a safer installation than a grounding-type receptacle with an equipment grounding conductor (if GFCI protection is not provided). This is because the GFCI protection device will clear a ground-fault when the fault-current is 5 milliamperes (+ or - 1 milliampere), which is less than the current level necessary to cause serious electric shock or electrocution."
"One of the methods permitted in 406.4(D)(2) is to replace a non-grounding type receptacle with a GFCI type receptacle. When doing this, the 2014 NEC required the "receptacle" to be marked "no equipment ground".
https://www.electricallicenserenewal.com/Electrical-Continuing-Education-Courses/NEC-Content.php?sectionID=306.0
Edits: 04/20/21 04/20/21 04/20/21
I had always assumed that a GFCI needed a ground to detect a fault.
Yup, I've battled ground loop issues for over 15 years... I have 115db Oris Horns and 45 SET Monoblocks, so any noise at all whether from a ground loop or a noisy tube will show up. My system is Silent Now.
I tried solving the ground loop problem the 'conventional ways', and improved it, but could not achieve the silence that I have now. The resistor on the amplifier input, which you referred to, did reduce it quite a bit on on one pair of 45 amps that I had, but did nothing on another pair.
The more I studied this problem, the more I found out that very few people really understand it. It only takes a few milivolts on an amplifier different from another component (preamp for instance) and my 115db horns will produce the sound that my amplifiers amplify. Is a ground truly zero volts or could it be .0001 volt -- My Oris Horns know.
The resistor on the amplifier input, which you referred to, did reduce it quite a bit on on one pair of 45 amps that I had, but did nothing on another pair.
I didn't mention it being at the input FWIW. But we do use this technique.
If it didn't work on one channel, it might be because something was grounding where it shouldn't have been in the other pair of amps? Its logical to assume that if it worked on one pair of amps that an identical pair would behave the same way. That they didn't suggests they were not identical...
No these were completely different Monoblocks... And it did not eliminate all of the hum, but reduced it quite a bit on both channels... When I got the new pair of Monoblocks, it had no effect on either channel. (i'm on my third pair of 45 SET Monoblocks now) -- Still own 2 Pair.I can't remember whether the resistor was on the input or not for sure. Ron Welborne gave me the suggestion (Which was about 10 years ago)...
Edit: -- I just opened up one of my Amplifiers and inspected the Resistor Mod. It was a resistor that was placed in series between the Ground on PS Regulator Board and the Star Ground on the Chassis.
Edits: 04/20/21 04/20/21 04/20/21
"will balanced connections ALWAYS solve Ground Loops?"
If you only connect the shield at one end, then yes. (as far as I know)
Tre'
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