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Properly designed, no current should run through it, but you can confirm that with the manufacturer, since you've been speaking with them. But don't necessarily remove the TT ground (you could experiment with that as well; sometimes a TT actually has less hum when not grounded, in my experience), as that's a different component coming into your preamp. The idea, I believe, is to use the preamp as a common grounding point with all the components that run into it so as to remove any hum or noise due to the different grounds; personally, when I had them years ago I tried my Sonoran cables with and without the grounds connected and noticed no difference, so I ultimately left the ground wires unattached.
Arcticdeth - rprince is correct - they are using the ground lead to ensure upstream source components do not cause hum.
Case in point - I had a Pioneer ELITE DVD player and a NAIM amp.
NAIM’s "architecture" assumes that all SOURCES are correctly grounded to the mains ground
The Pioneer however was "isolated" - it only had a two pin plug - and when used with the NAIM caused a loud hum. Measuring voltage between the chassis of the Pioneer and the mains ground with a multi-meter I was surprised to find a potential of 2 volts.
Grounding the chassis eliminated the hum completely.
Since several of todays source components (like DACs or Phono Stages) come with either USB power or Wal-wart power supplies they can often be the source of "noise".
At one point in time - all of my sources had isolated power supplies - so I implemented my own chassis grounding scheme - just to ensure it was as quiet as I could get it.
It does no harm to your components to implement this type of scheme - but if your components are correctly grounded it is not required.
I prefer to connect each "isolated source" to a central "grounding point" that connects directly to the ground of the power supply and not "daisy chain" it via other components.
I now have source components that are properly grounded so I no longer use this grounding scheme
I see no reason for the ground wire.
In the case of a piece of audio equipment that does not use the wall receptacle safety equipment ground, if the equipment was designed properly the signal ground of the piece of equipment is connected to the metal chassis of the equipment.
A piece of audio equipment where the equipment is designed to use the wall receptacle safety equipment ground the designer of the equipment may have or not have connected the circuit signal ground to the metal chassis of the equipment. Some designers incorporate a switch so the user can lift the signal ground from the wall safety equipment grounded chassis.
When an interconnect is connected between two pieces of equipment the signal grounds of the equipment is connected together by the signal ground return wire of the interconnect.
Any time a piece of equipment that uses the wall receptacle safety equipment ground, where the circuit signal ground of the equipment is connected to the metal chassis, and then connected to a piece of equipment that does not use the wall receptacle safety equipment ground, that piece of equipment also then becomes grounded to the wall receptacle safety equipment ground by the signal ground wire of the interconnect.
I suggest you look for another interconnect manufacture.
The fact that you do not hear a hum does not mean that there is no voltage differential between the different devices. Star grounding eliminates in the application of amplifier surgery on preamp level.
This comes from my comment recently on a thread about hum:
Every piece of equipment has at least two ground paths between them; the signal (RCA, XLR, not optical) cables and the power cords, often the speaker cables add another dimension. So star grounding is imperative (to eliminate voltage differences and hence current flow between the grounds of electric connecting devices). You can spend an huge amount on an ultra-high end box like the Troy Tripoint or try a DIY solution a la Audience adept Response or simply a brushed (yes it makes a difference) copper rod with 10ga copper wires to the units.
The interconnect RCA are mostly only grounded on the source side as the manufacturers know there may be a ground differential so they use use this workaround for, again from the ground differential point of view, possible deficient systems.
What you speak of is the shield of a shielded interconnect cable.
My post refers to the signal ground return wire of an interconnect.
Now in the case of a coax cable the shield and the signal ground return wire are one in the same and the shield must be connected to the connectors at both ends.
"Tannoy’s unique fifth
speaker terminal electrically grounds the driver
chassis, reducing potential sound degradation form
radio frequency interference. Eliminating potential
RF ‘noise’ enhances midrange clarity and allows
Definition to deliver an even more expressive
Are you using that? Where did you connect it to?
Since most components have grounded ac power cords and most interconnects have grounds, every component has two earth ground and thus ground loops. The third wire would add additional ground loops. All of this is to satisfy Underwriters Labs on the off chance that you have a loose power wire within the component and are grounded when you touch the component. All of this ruins your sound.
There are three alternatives. One is buying only plastic bodied component with the exception of your preamp. Two is using cheaters on all but the preamp power cord. In Canada cheater are illegal. You could also cut off the ground on the power cords other than that for the preamp. Third is having very low impedance grounds to one point that has a low impedance to earth or buy the Tripoint Troy Signature with filters on each binding post and a excellent ground. This is great but very expensive.
Norm, what about the Audience adeptResponse power conditioners with ground bars doing a similar job that the Tripoint Troy Signature do?
Cheater plugs have the inherent danger if something in the unlikely event mishaps in the device to the metal housing, the user touching the surface will act like a grounding wire which may be a shocking experience if he/she lives to tell.
Not sure "most" of audio and or video equipment designed and manufactured today use the wall receptacle safety equipment ground on all their equipment.
Just to name a few that do not use the safety equipment ground on all their audio equipment.
I am sure there are others.
It has nothing to do with whether the outer case is metal or plastic. It has to do with the insulation used on the AC internal power wiring. Equipment that is designed and Listed for only 2 wire power cords that does not use/need the third wire safety equipment ground uses double insulated AC power wiring. It does cost more than regular insulated wire.
In time, jmho, all audio equipment as well as video equipment designed and manufactured for the home consumer use will use 2 wire power cords.
There is no need for the safety equipment ground wire today and it can/does degrade the sound of audio as well as video equipment. Manufactures just need to spend the extra money and use double insulated AC power wiring in their equipment.
Star grounding devices like Troy Tripoint Signature (Norm you own or at least owned one) and in lesser extent Granite Audio Ground Zero do contribute with impedance ground matching. That brings us back to OP's question about ground loops.
Or is it the fact that the absorption of EMI and RFI within the Tripoint Signature (the same rationale goes for SR Powercell) that is the main contributor to improved sound?
Both the SR Powercell and Troy Signature are known to be black boxes, no nudie of their models (pun not intended) on the web available, one contains the "trickled down Powercell" technology and the other some passive filters and magnets (HFC is pulling hard, pun intended, in this direction). The Troy Master Ref adds at least a AC waveform corrector so part of the 60s technology is added (BTW I have a vintage Elgar 6006B - usually under 1k on Ebay- that acts as isolation transformer and AC waveform corrector for that for my upstream equipment.
I never had any of them in neither of my systems so would like to hear Norm's comment on the benefits of star grounding vs EMI/RFI rejection/absorption.