Cheryl,
in that link did you find any mention to 0V Reference/signal ground or RCA phono interconnect type cables (only reference I saw was comment about cable shielding was 'no connection to earth (or even circuit
common) is needed for shielding to be effective' that is not completely applicable in terms of scope and focus-requirements), isolating signal ground from power supply, stray field transformer EMI situation?
Regarding speakers, I do not know if Tannoy is the only one but they provide an earth terminal, subjectively those that have used it seems to suggest that it can help sound quality but yeah that is subjective.
Thanks
Orb
Section entitled 'Loaded Words That Cause Misunderstandings' discusses the concept of shield, earth, signal grounds and the ground plane under an antenna etc. This is all very basic stuff but unfortunately for the non-engineer type the concepts are probably foreign and only marginally comprehensible without some in-depth discussion of electronics if not physics.
Section entitled 'The Pin 1 Problem' indicates potential problem when cable shield is connected to a signal ground out of convenience, ignorance, or some other aspect not generally conducive to signal integrity instead of to the case. No distinction is made between balanced or unbalanced although the problem was originally named after the XL(R?) pin 1 terminal.
I suppose grounding the input terminals might have some benefit if it addresses the 'pin 1 problem' by adding a solid connection to the case, but that would involve actually tying the connector right to the case where it penetrates, not tying it to a box somewhere outside of the case. That makes no sense in the context of this article nor does it make any sense to me based on what I know.
Unfortunately, in some cases even case grounding is not such a simple thing. I have worked on amplifier where moving the terminal strip with the power supply case ground connection on it just a few inches from where the manufacturer attached it originally completely messes up the s/n so apparently it had to be tuned by the designer to optimize its effectiveness.
This was low-power Fender tube amplifier (12" speaker) with all the wiring inside a metal chassis and all the larger components mounted above the chassis with connectors penetrating the chassis.
I never did figure out why the case ground connection was so sensitive to location. This was before my course of studies and such amplifiers are no longer available for me to investigate further since I no longer really play or have access to such amps needing repair. One of them had a broken case connection and when I re-attached it with a jumper cable I quickly discovered just how sensitive that connection was. I tried soldering it with a short lead and moving it around because it never really did quiet things down completely no matter where it was placed. It had to be replaced exactly as originally built or the amplifier hummed quite audibly. When replaced at its original location there was only a quiet buzz.
I also worked on amplifiers where the case ground connection is tied in at the corners of every PCB on the mounting screws. These were solid state. As far as I can tell, every single one of them has the so-called 'pin 1 problem' because the RCA jacks are universally mounted to either bakelite (older equipment) or plastic (newer equipment) and the ground connection ties directly to the circuit board, not the case.
Nearly all of these amplifiers are in wooden or plastic cases too so there is no shield to connect to anyway except maybe (not necessarily) the metal chassis (if it has one) that does not really shield anything at all when it consists of only an open frame and/or most of the components if not all of them exist on the outside surface of the PCB, above any potential power and ground planes (if the PCB even has such - many power amps have only top and bottom layers with almost no shielding in the PCB at all).
Any shielding in such amplifiers is localized to the area that requires it and the rest is designed out for cost reasons. There really is no global 'case' to connect the RCA shield to anyway and it boggles me why hanging a long heavy wire off the unused input connectors does anything except add more antennas to a system that already has a marginal capacity to reject noise anyway.
In such amplifiers it makes no sense to run the RCA shield terminal back to the internal star connection either since the PCB trace or ground plane is usually heavy and short enough to take it straight to the chassis via PCB corner screws.
My Onkyo receivers all have metal case that is sort-of a shield, but not completely since it has lots of penetrations for air holes and plasma display panel. I am not sure if my Onkyos isolate the RCA jack at the case penetration. I only removed the HDMI to repair the failed local regulator capacitors (Onkyo HDMI is known for this problem) and ignored everything else.
If the RCA are screwed to the case it cannot be individually like the way the HDMI are done. It would have to be from a common connection or two because there are simply too many of them to put a screw through each one.
For some televisions the chassis is hot and must be kept isolated from the RCA shields. In that case there is some other technique employed that I am not aware of to float the signal ground from the chassis and all the controls are either insulated push buttons or for older equipment plastic shafts on all the controls with the metal mounting nut and chassis concealed behind the plastic case to ensure no one gets killed even if a knob falls off.
Regarding whether or not it is safe to connect speaker terminals to a ground bus, that depends on if the amplifier makes a hard connection from the terminal to the case/power/signal ground star connection internally or not. For some amplifiers, both the output terminals on a channel are driven and it might not be a good idea in that case.
For some amplifiers, there may be signal transmitted or received on the negative speaker output terminal (even though it routes back directly to the case/power/signal connection) just because of the impedance of that connecting path and the current flowing through it. Transmitters might be the speaker itself that is sinking current back through that negative terminal or some other component like a transistor in the amplifier that could either be sourcing current into that path and/or using it as a reference in which case it is a receiver. In either case I cannot see any benefit to routing a ground connection between speaker terminal and line input shield so I assume this is not being done or it could cause problems even if it passes through an external box on the way. Replies on the thread indicate that separate boxes are used for line level vs power output and in my frame of reference that only makes sense because to do otherwise might be playing with fire.
Similar considerations apply to input stages. Tying unused inputs to a thick external ground wire has the potential to inject some sort of noise into the signal ground because of that 'pin 1 problem' and the more connections there are to that external box the lower the impedance of the injection path while the longer the connecting wires are and/or the more of them there are, the larger the potential antenna doing the injecting.
At least they are all going to be referenced to some common node, hopefully? In that case the risks are less than the risks that arise from connecting even more components/antennas to those inputs that could inject even more noise, but I do not see how grounding those connectors to an external box does anything to improve the s/n especially if they connect to DC isolated metal plates in some container.
Ideally they want to be referenced directly to their own internal signal ground or at least to local case ground if there is current coming in on those shields that could upset the signal ground. It almost seems as if the whole point of using isolated plates inside a grounding box (if that is what is happening) is to avoid connecting to anything at all.
It seems to me that the entire box is just cosmetic or at best a high frequency capacitive coupling scheme though the capacitance will be small even with very large plates if the dielectric between them is thick and then how do you decide what order to attach your components to the stack of plates? Who lives on top, who is on the bottom, who is in the middle, and does it make a difference or not? If it really does anything at all there must be some interleaving of the plates for symmetry or the order of connection might change the performance.
I just do not get the concept based on the info available. In any case, such grounding decisions need to be made intelligently and with deliberation if not measurements.
Sometimes it is not clear why one scenario works and another does not. I am no physicist and even modeling microstrip or stripline in a simulator is taken care of for me by the big guns who designed the simulator. Add dimensions and push the 'run' button. Even 3D field simulators are similarly designed to be more user-friendly in terms of model assembly and not so much explaining how it derives the resulting response. For that, a solid technical education with specialization is required and that probably involves equivalent to Ph.D in physics as well as solid mathematical programming skills and maybe a team working on the product through its entire design cycle.
Modeling an entire metal case with all the penetrations and such is basically impossible with a complex shape. Like analog simulation of thousands of transistors, field simulations of highly complex shapes become unworkable both from convergence issues and computational intensity let alone the inaccuracies of the model. It gets difficult very quickly and the only way around that is to break the problem down into pieces that the simulator can handle efficiently and accurately while plugging in rough approximations for things like current sources or entire signal blocks (in the case of analog simulations anyway that I have direct experience with).
I just cannot imagine anyone designing a grounding system that attaches outside of the cases of individual components that can actually have a beneficial impact unless it is customized to the system if not part of its initial specification. I have never encountered any such animal before in my entire existence.
Maybe someone figured out a way to do it. I am willing to be convinced. I am not going to trust even my own ears for it though unless I can see a marked change in measured performance or hear an incontrovertibly dramatic or at least detectable difference via DBT and even in that case I still want measurements to tell me what I heard to prove it was actually beneficial and not degradation. Given the range of system topology that is possible with arbitrary specification of all the components making up the system, it seems that even if there is potential benefit, that benefit is goingto be so highly system dependent that results would be all over the place.
As I was indicating, the actual grounding decision/device that makes the improvement might be any one of many things and just tossing a bunch of modifications and additions at a system with some rote approach seems to me likely to fail objective evaluation based on my experience. This is why I keep asking about instructions for installation. I want to know if the specific details vary based on components and topology, or if it just consists of a bunch of boxes with a single recipe for connecting them all up.
