Another grounding problem-need advice.

[AndrewT]

Hi,

let's put my cards on the table by specifying my rules right off.

ALWAYS connect safety earth to exposed conductive (metal) parts of mains powered equipment.
NEVER temporarily break your safety earth connection while still plugged into the mains.
NEVER apply a ground lift switch to the safety earth connection.

Now some recomendations.

You do not need to connect audio ground to safety ground.
You do not need to link audio ground to safety ground with a disconnecting network.
You can include a ground lift switch as part of the disconnecting network from audio ground to safety ground.
Keep the charging currents in a mains PSU away from the audio ground.
Link all the power (dirty) grounds together.
Link all the relay and ancilliary (very dirty) grounds together.
Link all the digital grounds together.
Link all the signal (clean) grounds together.
Link all the separate ground to a central star ground.
Do not put your central star ground on the common connection between the smoothing caps of a dual polarity PSU.
Optional, link the central star ground to the safety ground using a disconnecting network (NOT directly).

 

[darkfenriz]

Thanks Andrew 😉

 

[richie00boy]

I think your signal ground and power ground should be a direct connection with as short a loop as bla bla bla...

No "lifts" there at all.

Chris, you mean as simple as:

Absolutely agree. Any lift is an error introduced.

 

[sagarverma]

Thanks Andrew T for these points.

Sagar

 

[richie00boy]

Good must do's and recommendeations from Andrew.

But I think there needs to be some clarification on these points:

You do not need to connect audio ground to safety ground.
You do not need to link audio ground to safety ground with a disconnecting network.

You do if you want to retain RFI immunity. But often the hum is a worse problem than RFI so it's a matter of choosing the lesser of two evils.

Do not put your central star ground on the common connection between the smoothing caps of a dual polarity PSU.

What he means is don't put the star right in the middle of the caps because of the charging currents. Put it centrally but on a small 'branch off' from the centre.

 

[FastEddy]

worth repeating

AndrewT:
"ALWAYS connect safety earth to exposed conductive (metal) parts of mains powered equipment."

"NEVER temporarily break your safety earth connection while still plugged into the mains."

"NEVER apply a ground lift switch to the safety earth connection."

Yes! ... what he said ... and .... I have added some to his recommendations ...

"Now some recomendations.

You do not need to connect audio ground to safety ground.
You do not need to link audio ground to safety ground with a disconnecting network.
You can include a ground lift switch as part of the disconnecting network from audio ground to safety ground. ( BUT you do not need to ... and ... be sure to see rule # 3 above.)

 

[darkfenriz]

Guys
beer for you!

The connection that Chris has suggested works for me well with no hum and no distortion. Same as disconnecting earth from amp, but more elegant of course.

Thanks for all your input
Adam

 

[classd4sure]

Guys
beer for you!

The connection that Chris has suggested works for me well with no hum and no distortion. Same as disconnecting earth from amp, but more elegant of course.

Thanks for all your input
Adam

As per my grounding issue.. all I need is a hacksaw.