understanding star grounding

Dear Mark,

I've used GBR's in my main amps. But would not know were using them in buffers (circuit below).

I've tried as much as possible to create full mono preamps. However, the muses 72320 chip has only 1 ground. So I have to start from there again forwards with 2 GND traces or wires.
 

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ok, after reviewing a number of threads, i have a general understanding of what my star grounding should look like

however, after seeing a number of different diagrams, there seems to be some slight conflict

one of the later and final diagrams of this thread (ignoring the fact that they are dual mono) shows the RCA shield and Speaker Negatives, going BACK to the amp module before passing to the star ground

1668541299212.png


however, on this page we see a mostly similar, but the RCA shields and Speaker Negatives go right to the star ground, and not going back through the amp module GND

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so which is it? also, seeing as many/most have a protection module, i figured we'd want to address that as well?

let's play 'fill in the proper grounding and earth lines for this setup'

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wire up ONE amp only, WITHOUT the protection board, and tell us what you get.
pure dead silence, like ear millimeters away from the speaker, couldnt even tell it was on. i left the protection board in place so it was one less thing to mod, and with how quiet it was, it didnt even bother to take it out of the equation (which i've done in other tests)

waiting for the caps to discharge and going to test the other side

on another note, i shorted the shields on the RCA inputs (when both modules hooked up), and that made a very large difference compared to without, however audible noise at about the 8-12" to the speaker with that configuration. i will admit however that this was done with just alligators, perhaps actually soldering a proper wire would potentially yield better results

edit: testing the other side, basically the same dead silence, maybe a tiny grumble noise, but you practically have to have your ear touching the tweeter to pick it up

hooking both back up, with a better location on the alligators for the short of the rca jackets, and it's a bit better noise wise, maybe audible within 6-8". i'm wondering if just adding a 0v to earth/gnd with a breaker circuit will help? or perhaps a cap or resistor on the input?

short was added between RCAs (largest improvement thus far, hot pink line in diagram), wondering if the line in bright blue would be needed to finish knocking down the rest of the noise

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several documents from member Bonsai website that are well worth reading:
https://hifisonix.com/ground-loops/

p.s. i trust your diagram is in error when showing amp2 gnd tee'd into amp1 gnd :unsure:
i updated the diagram to potentially reflect the GND on the amp1 and amp2 which meet at the GND output of the SMPS

this is my next revision based on some feedback from others

1) adding a 10R resistor on the RCA bridge (pink)
2) adding in the elliott breaker circuit (light blue)
3) someone is proposing running a short on the GND on the protection board (purple)

thoughts on each of the 3 above?

1668716203431.png
 
Hope this helps

FROM ONE VIEW
1. Ideally source devices and preamplifiers should behave like pickups, be it microphones, tape heads and cartridges.
2. We expect that the output levels are safe.
3. As such their reference plane should not be connected to the chassis. However it may offer a shield plane for the signal, however this should not be connected to the chassis.
4. As per 1 any exposed chassis offers no danger and essentially behaves as a faraday cage. Devices having lethal voltages such as tube preamplifiers will have an earthed chassis. No connection exists between this chassis and signal ground. This chassis could essentially be an earthed faraday cage.
5. Thus even integrated preamplifiers should have a separate power supply not connected to the amplifier main power supply or they can have a shared power supply with only one earthing point with no connection to chassis. Ideally an integrated preamplifier has only one earthing point. The inputs and outputs. The upstream device if any should also have an isolated supply and should behave like a pickup.
6.Power amplifiers may have the amplifier power ground connected to chassis earth, however if such an amplifier will be used for other purposes a ground lift switch may exist to separate chassis ground from amplifiers power ground.
7. A partial chassis may act more like an antennae and so depending on dimensions, limiting the bandwidth of the amplifier should address this problem as audio wavelengths are much longer and so the temptation to also use the chassis as a ground plane is always at hand. The journey of equipment matching continues.

FROM ANOTHER VIEW
Proper earthing/grounding/shielding of electronics plays two roles
1. Noise reduction and better signal integrity
2. Electrical safety Starting with the analogy of the coaxial cable that requires a 50 Ohm or 75 Ohm terminator at one end then we can start to understand the problem. For single rail electronics, the negative rail plays the role of earth. For dual rail electronics, the zero volt rail serves as earth. If the potential difference between the power supply rails of an electronic circuit are within safe levels for touch and also the power is from a battery or an isolation transformer where the primary coil will never cross with the secondary coil even under fault, then such a circuit may use a two pin A/C connector and have a floating earth. In such devices the ground plane as well as the chassis are connected together. Where the chassis is exposed to possible electrical connection to other devices either through input earth, output earth or the chassis itself to an equipment rack. With our initial coaxial cable analogy the problems encountered with 10base2 networks come into play. Only one end of a 10base2 network was earthed. In our audio example we can manage our ground loops by increasing resistance through paths which we don't want currents to prefer.
To better manage ground loops and other problems, we terminate at only one point that is between the chassis and the power supply ground terminal. Chassis consists of the enclosure, heatsinks, and the transformer iron core. The resistor used at this termination point can be anything between 100 to 10 Ohms depending on the currents at play. Where we want to create an AC short for certain high frequencies we bypass this resistor with a suitable capacitor between 10nF to 100nF.
For electrical safety we also bypass this parallel resistor and capacitor with a pair of parallel diodes each oriented in the opposite direction. These are high current diodes capable of remaining intact while the AC fuse blows incase of a fault condition. These diodes also feature a high forward voltage for higher perceived resistance. Two pin equipment does not protect the user from external electrical faults that come into contact with the chassis.
For three pin equipment the earth pin is connected directly to the chassis. Any dangerous fault will blow the fuse disconnecting the dangerous voltage. At the circuit level the electronics are mounted with isolating standoffs if using plated holes or holes that do not completely clear the circuit ground plane. Brass or non isolated standoffs may be used where the mounting holes have no electrical connection with the PCB ground plane. For further noise and interference management the circuit should feature power supply high frequency decoupling capacitors especially across opamp IC power pins. These capacitors work hand in hand with input high frequency filter capacitors. High frequency noise management for PCBs having external inputs may be further improved with termination at the circuit level between circuit ground and chassis using a capacitor at least 10x smaller than our main terminator bypass capacitor and a bleeder resistor at least 10x greater than our main terminator resistor. In signal transmission between audio circuits, the transmitting end shields the signal with its earth, some manufacturers terminate high frequency noise at this end but it all depends on whether the transmitting circuit is using negative feedback or not. With negative feedback it may be unnecessary. On the receiving end it matters whether or not the receiver has high currents on the circuit that are a magnitude higher than the transmitting equipment? If so the receiving circuit will try to isolate these currents with a small resistor value separating the grounds. It is also at the receiver where we terminate and filter high frequency noise. There are other factors to consider for every circuit including the topology.