Help with Star Grounding

[datrumole]

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

good thread here , one of the later and final diagrams (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

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

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'

 

[voodooless]

Why would you do any of this? Do you have a grounding problem?

In any case, connecting speaker - to ground will potential damage your amp. In many amps, the speaker - is not ground at all.

 

[datrumole]

Why would you do any of this? Do you have a grounding problem?

In any case, connecting speaker - to ground will potential damage your amp. In many amps, the speaker - is not ground at all.

I'm having a ground loop problem currently

these are strategies based on a number of papers on how best to ground and wire your equipment to ensure no ground loops are created

perhaps if you drew the lines you feel are necessary in the blank template provided I can compare it to how I'm currently wired

 

[voodooless]

First thing to do it determine where the ground loop actually comes from. If the source is known, the fix is often not far away.

What amp are we talking about? What and how is the source connected? Do you also have a loop if you short the RCA inputs? Does it happen with other sources?

 

[datrumole]

First thing to do it determine where the ground loop actually comes from. If the source is known, the fix is often not far away.

What amp are we talking about? What and how is the source connected? Do you also have a loop if you short the RCA inputs? Does it happen with other sources?

Ive tested with a topping e30, cell phone, and computer as a source, all produce a noticable hum

I have not shorted the RCA shields to one another but to the chassis ground, and the hum got worse. I can try shorting them out to one another, however do I still keep them connected to the signal in (-) while I do this?

one thing I did remove was the earth/ground from the mains to the SMPS (leaving the earth/ground to chassis in tact)

 

[voodooless]

So, what’s the equipment we’re talking about here?

 

[datrumole]

So, what’s the equipment we’re talking about here?

apologies

smps - connex smps500r
protection - https://www.aliexpress.us/item/2251832679254695.html
amp modules - (2) L20.5 mono boards

 

[voodooless]

Okay, so clearly the loop is from inside the amp.

I would start with wiring properly. RCA GND to input GND, RCA + to input +. Then amp + to terminal +, amp - to terminal -. If you have the protection in between, also fully wire it. Isolate RCA and terminal from chassis.

Wire SMPS +, - and GND to the amps. Connect AC earth to chassis and SMPS.

 

[DonH56]

What @voodooless said.

A star ground is not always the best solution, particularly for a ground loop and single-ended signal paths. Current is a loop, so you want the signal (+) and (-) paths the same, potentially independent of system ground. The problem is that doing something like say running signal (+) from input to amp and then amp (+) to the output with the grounds (signal (-) ) routed off to a star ground creates a different, perhaps longer path for the return current, and can cause the input to be modulated by the output. If you are building modules in a DIY component, the manufacturer should provide guidance about optimal signal routing.

For a bit more on ground loops, there is this: https://www.audiosciencereview.com/forum/index.php?threads/ground-loops-101.7162/

HTH - Don

 

[voodooless]

And as for star-ground, read this:

https://www.hypex.nl/img/upload/doc/an_wp/WP_The_G_word.pdf

 

[datrumole]

Okay, so clearly the loop is from inside the amp.

I would start with wiring properly. RCA GND to input GND, RCA + to input +. Then amp + to terminal +, amp - to terminal -. If you have the protection in between, also fully wire it. Isolate RCA and terminal from chassis.

Wire SMPS +, - and GND to the amps. Connect AC earth to chassis and SMPS.

this is exactly as i have it now, hums like a bird

And as for star-ground, read this:

https://www.hypex.nl/img/upload/doc/an_wp/WP_The_G_word.pdf

class d, and more sophisticated modules like hypex, ice, pascal have a more robust topology compared to just the L20.5 which is just a raw AB amp

however, even the icepower ASP modules recommend some form of star ground

What @voodooless said.

A star ground is not always the best solution, particularly for a ground loop and single-ended signal paths. Current is a loop, so you want the signal (+) and (-) paths the same, potentially independent of system ground. The problem is that doing something like say running signal (+) from input to amp and then amp (+) to the output with the grounds (signal (-) ) routed off to a star ground creates a different, perhaps longer path for the return current, and can cause the input to be modulated by the output. If you are building modules in a DIY component, the manufacturer should provide guidance about optimal signal routing.

For a bit more on ground loops, there is this: https://www.audiosciencereview.com/forum/index.php?threads/ground-loops-101.7162/

HTH - Don

thanks don, i've read a disturbing number of threads on ground loops. one of the guys who sort of 'wrote a complete book on it' even mentions star grounding, so i'm just unclear. i think also that a lot of integrated PSU/Amp modules have a MUCH simpler wiring diagram from those using separates. as i've built the icepower ASP modules and did NOT have to deal with any sort of star anything (despite their documentation above stating otherwise)

 

[voodooless]

Can you remove the AC earth? Not that you should do that permanently, but just to see what it will do?

Did you try without the protection? What if you only have use amp?

 

[datrumole]

Can you remove the AC earth? Not that you should do that permanently, but just to see what it will do?

Did you try without the protection? What if you only have use amp?

so, removing earth/ground to the SMPS (and leaving to the chassis) actually made a decent improvement. removed some hiss, not the hum. however, mounting holes 1 and 2 on the SMPS are earth/ground connected, and by nature with the standoffs being brass, and screwed directly to the chassis, it appears to be redundant?

also note, direct from connex documentation shows a star ground with R/C method

i completely disconnected the protection board and bypassed it, no change

 

[voodooless]

so, removing earth/ground to the SMPS (and leaving to the chassis) actually made a decent improvement. removed some hiss, not the hum. however, mounting holes 1 and 2 on the SMPS are earth/ground connected, and by nature with the standoffs being brass, and screwed directly to the chassis, it appears to be redundant?

The SMPS mounting holes are connected to the AC earth indeed, so that should be redundant. The secondary side of the SMPS however is fully isolated.

My guess is the amps are still connected to the chassis via their respective mounting points? What if you isolate those?

 

[datrumole]

The SMPS mounting holes are connected to the AC earth indeed, so that should be redundant. The secondary side of the SMPS however is fully isolated.

My guess is the amps are still connected to the chassis via their respective mounting points? What if you isolate those?

i'll confirm, but i dont believe the mounting holes on the amp holes are earth/ground connected, but i'll unscrew and see

 

[voodooless]

Ah, wait, the SMPS GND is connected to th AC earth via that 10R resistor. I missed the earth symbol right next to the transformer output.

Can you check with a DDM if you indeed measure 10R? If it’s lower, then there is an additional connection somewhere.

 

[Sokel]

however, even the icepower ASP modules recommend some form of star ground

View attachment 243578

Not in the new 1200as2,300a2,etc:

 

[datrumole]

Ah, wait, the SMPS GND is connected to th AC earth via that 10R resistor. I missed the earth symbol right next to the transformer output.

Can you check with a DDM if you indeed measure 10R? If it’s lower, then there is an additional connection somewhere.

good news, i took the first suggestion on shorting the two RCA shields, and we have a massive improvement! going to go test with the e30 where i had the most amount of hiss/hum shortly

with the RCAs shorted, i went back and did a test connecting earth/gnd from mains to SMPS. it gets worse when the earth is connected

that pic of the R/C coupling above is not something i have in my circuit unless it's on the SMPS board. doing a DMM from the earth/gnd input and the chassis, i get a 0.0ohm reading

we now look like this

 

[Doodski]

doing a DMM from the earth/gnd input and the chassis, i get a 0.1ohm reading (open circuit)

What do you mean by "Open circuit" in reference to a 0.1 Ohm reading?

 

[datrumole]

Not in the new 1200as2,300a2,etc:

View attachment 243591

perhaps not, my pic above is direct from their ASP (A) lineup integrators guide. plus when you have the SMPS integrated like in some of those (not sure if that module does or not) they have taken care of all that nonsense for you. also a lot of those modules use balanced inputs which is a MUCH better situation than i am in