Grounding ?

A cheater plug is a good idea for testing. Not sure if its a good idea to use it permanently. To float the grounds in my system, I put a piece of electrical tape on the ground prong of the IEC connector on my transport and DAC. That way when I plug in the power cord, there is no contact for the ground. My preamp is passive, my TT uses a two prong power cord, so the only gear using three prong connector is the amps.

Having all your gear grounded via electrical outlet can create problems on some systems. To eliminate hum/ground loops only one component (usually the preamp) needs to be grounded and anything else connected to this unit via interconnects will become grounded as well. This is more desirable.

Thanks for the response guys! I just looked at the back of my Rega and it does not have a ground coming out of the back of the unit so I'll try lifting the ground on the pre-amp instead of the amp. How can I insure the tap does not push back on the IEC when I push the cord in?

Thanks,
Wig

---> Bob,
why relying on grounding through mass of interconnect cables is bad idea?

I have preamp and two monoblocks - all with unbalanced connection only. Ground is connected to the chassis internally. I have mains cord grounded only in preamplifier. Both monoblocks have lifted ground in power cords and are grounded through interconnects and preamplifier's power cord.
All hum disappeared and such connection seems to be safe (monoblocks are grounded through preamp). What is wrong in such approach?

Shock risk; possible inadequate wire size when ICs serve as ground; noise from having ground current flowing through ICs.

(1) If the amp should develop a problem that puts live AC on the chassis, the fault current will be flowing through the IC. Depending on the level of the fault, it may not be enough to trip a circuit breaker, but still be enough to electrocute you (all it takes to stop your heart is a few mA of current). You could be electrocuted from coming into contact with one end of an unplugged IC and chassis of the amp or other component connected to it.

(2) The shield/ground wire size in an IC may not be of a size adequate enough to carry full ground fault current, which can be greater than normal.

(3) Small ground currents flowing through ICs can create the very noise you're attempting to solve by lifting ground in the first place.

Thank you for the answer.
So, what is a solution?
Is the isolation transformers like Jensen Transformers are the only solution for full unbalanced system?
Honestly I do not know any person who use it.

Is a possible fix, and this is JUST a question, that 1 or more pieces has an internal hot/neutral swap?
Could you tell somehow? Maybe have all gear plugged into the wall without any I/Cs. Than measure for voltage between the chassis or ground of each piece? If there is a voltage between chassis of 2 pieces, isn't that a hot/ neutral swap?

Does everyone own an outlet tester? The type w/3 leds to indicate various good / bad conditions?

Which raises another question, why do some amp manufacturers include a ground lift switch. The answer is very simple because they know it can be very convenient to flip a switch to lift the ground to avoid hum caused by a ground loop rather than buy and use a sound degrading cheater plug or cutting the ground pin off the power cord.

Note: When using some tube preamps, I have had to lift all the grounds on all components except for the preamp to eliminate hum or considerably reduce it. The other thing to check is to make sure all power cords are not too close to the interconnects.

Mike Elliot talks extensively about ground loops and hum on his Alta Vista website and recommends all except one component be grounded and if a ground fault occurs in any system component it can be safely drawn away by the interconnects via the one grounded component. I think we can trust this excellent designer who has been producing quality gear for many years.

Charles Hansen of Ayre also advocates floating the grounds.

Which raises another question, why do some amp manufacturers include a ground lift switch.
08-09-09: Phd

The switch only lifts the signal ground from the chassis. Never the safety equipment ground from the chassis/enclosure.
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Jea48, this could be true, but before agreeing I would like to research it. You already know that many preamps as well as power amps are two wire, that don't provide a third wire for grounding. In addition there are non-shielded interconnects that only use the center wire. Not observing how your interconnects are designed as well as your gear could produce the perfect storm.

Bob_R
I believe your statement would be true IF there were no hot/neutral reverse wiring. I do NOT mean the outlet, the condition of which is easily seen with an easily purchased outlet tester, but internal to each piece of gear. Does that make any sense?

There can only be current flow if ground potential is different between each piece. An easy way to determine this would be to plug everything in than measure chassis-2-chassis with a decent DVM.

Given the sensitivity of the gear involved, there doesn't have to be much current, either.

If you're really paranoid you can simply connect the chassis of the primary grounded component (typically preamp) to the chassis' of other componentry. Any reasonable size (black insulation color for appearance) (14awg & stranded for flexibility) household electrical wire with spade or ring tongue crimp lugs should be more than sufficient. Basic creativity should suffice; loosen a chassis screw on the back panels & tie the lugs thereto.

However if it was me I absolutely wouldn't bother (take a hint from Milimetr) but I would never advise someone else against safety grounding for liability reasons alone. Perceive the implication, vs. the statement. In regard to sound quality now that's the issue, which many might be more likely to focus on.

Yes you can simply voltmeter-probe to the chassis, with the other probe referenced to an AC outlet ground, to check for stray leakages. The compoment would be energised but not cabled to anything else. You need to probe on a bare metal surface or press the probe tip down hard to penetrate the paint; judiciously of course and in a strategic location (such as the bottom panel) so as not to harm the finish.

Bob_b
Yes I am paranoid, but that doesn't matter in this case.
My personal system has NO hum or other internal noise issues.

My recommendation is to check NOT to ground, but between system components. IF there is voltage present, I would consider swapping hot/neutral where the power pigtail gets to the first terminal strip or whatever.
Once everything agrees, the hum should disappear?

My recommendation is to check NOT to ground, but between system components. IF there is voltage present, I would consider swapping hot/neutral where the power pigtail gets to the first terminal strip or whatever.
08-10-09: Magfan

If there is a difference of potential, voltage, from one chassis to another then there would indeed be a current flow when the two chassis are connected together by ics.

If the AC polarity is reversed and not correct on a piece of equipment that could cause a higher potential, voltage, from that piece of equipment to another piece of equipment where the AC polarity is correct. I would think the difference of potential would be there whether an equipment ground was used or not. Jmo.....

Something that should be made clear when measuring AC leakage of the primary winding of a power transformer the measurement is actually referenced to the neutral conductor.... The neutral being the grounded conductor which shares the same ground plane as the equipment grounding conductor. That is why most people measure from the chassis to the equipment ground of the recept. But the actual difference of potential is being measured to the neutral.
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Exactly, J,
there will be voltage present if the ground plug is used or not! Connecting 2 pieces under these conditions is using 1 of 'em as 'local ground'.

Please explain 'leakage'. I have heard the term but am unfamiliar with its use in this case.

Have I just been lucky all these years in NOT ever having a bigtime hum problem?

Please explain 'leakage'. I have heard the term but am unfamiliar with its use in this case.
08-10-09: Magfan

Charles Hansen on the subject.

1) Reversed AC polarity -- All power transformers have an inherent asymmetry to their construction. The primary winding comprises multiple layers, so that one lead is connected to the innermost windings and the other lead is connected to the outermost windings. This means that one lead has a higher coupling capacitance to the core of the transformer. Please remember that the AC supply is also asymmetrical, with the neutral lead essentially being at ground potential (assuming there is not a fault in the house wiring). The result is that one orientation will give a higher AC leakage current to the chassis of the amp (and worse sound) than the other orientation.

Not all transformer manufacturers use consistent markings on their transformers so that the correct orientation can be identified, and not all amp manufacturers pay attention to this even if the transformer is correctly marked. The result is that many audio products have a random chance of being correctly oriented.

http://www.audioasylum.com/audio/general/messages/449743.html

Sean.... thread here on Agon.
http://forum.audiogon.com/cgi-bin/fr.pl?htech&1014011751&openusid&zzSean
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