Which grounding scheme is better?

[smithomo]

Hi Friends,
Please give me your comments with 2 difference grounding schemes I have draw here.

Scenario1:
This one is what I have learnt from forum here and other articles, it is also like adding "T"s and connecting each branch ordered as below. They are grounded to a single pcb line and then to the quieter side.

An externally hosted image should be here but it was not working when we last tested it.

Scenario2:
Almost the same as above, except the circuit grounds on the left(I called quietest) connected to the middle point(center tab) and the dirty current from Caps connected on the right, so noise current can flow between transformer center tab point and caps.
I'm personally thought that the amp circuit can working on the cleaner grounding.
Am I right? please give me your comment(s).
Thanks.

An externally hosted image should be here but it was not working when we last tested it.

 

[DF96]

Scenario 1 is the better of the two. 2 is wrong; it adds the voltage drops from ground currents to the supply rails so makes them unnecessarily dirty.

C1 should be grounded at the quiet end.

 

[smithomo]

Scenario 1 is the better of the two. 2 is wrong; it adds the voltage drops from ground currents to the supply rails so makes them unnecessarily dirty.

C1 should be grounded at the quiet end.

Thank you, so #1 with change c1 connect to the quieter.

1 more question, which point is best to connected to another channel PCU ground?

 

[DF96]

If you need to connect two quite separate PSUs then always do it at the quiet end. Better still, let each PSU feed its own circuit then connect the signal grounds together.

 

[nigelwright7557]

Its still possible with the best circuit you might get hum.
I found I needed an RC between the output transistor and the LTP transistors on the power rails. Otherwise on quiet passages I could hear hum.

 

[smithomo]

Its still possible with the best circuit you might get hum.
I found I needed an RC between the output transistor and the LTP transistors on the power rails. Otherwise on quiet passages I could hear hum.

Ok I added Zobel networks.

If you need to connect two quite separate PSUs then always do it at the quiet end. Better still, let each PSU feed its own circuit then connect the signal grounds together.

I add another channel amp and also with seperate PSU but take the same transformer.

Both quiet points are connected as your advise.

So is it the place to connected to the chassis?

An externally hosted image should be here but it was not working when we last tested it.

 

[DF96]

Running two 'separate' PSUs off the same secondaries is almost impossible to do quietly- the return currents get badly mixed up.

In simulation where all the caps have the same value and all connections are zero ohms it may work OK. Real life is different.

 

[Bensen]

Hi Smithomo,


Regarding post nr6, that's the way I did it on my last build. Must admit that there is a small audible hum when keeping your ear against a speaker.

I did not try what the effect should be if I would connect the input signal ground directly to the star point. I used 10r resistors as you have drawn.

See post 2837
http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-284.html

 

[AndrewT]

If the two amplifiers inside a common chassis are not isolated from each other, then I believe it follows that the two amplifiers MUST be connected to the same Main Audio Ground. This condition DEMANDS that the Signal Ground MUST be separate from the Power Ground on each amplifier.

 

[smithomo]

Hi Smithomo,


Regarding post nr6, that's the way I did it on my last build. Must admit that there is a small audible hum when keeping your ear against a speaker.

I did not try what the effect should be if I would connect the input signal ground directly to the star point. I used 10r resistors as you have drawn.

See post 2837
http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-284.html

Hi Bensen,
First, you amp look so nice and good circuitry.
Are all cap pins from both channel PSUs are connected to to the same star ground point?
I saw you have 2 separate rectifier boards, so I think it hardly to connect all of them(include diode pins) together to the real single point.
I planned to do it this way for the low power regulated PSU to drives gain stages.
Because of my current mode-VAS is really low PSRR, that the reason why I want to have separation.

 

[tiefbassuebertr]

If you need to connect two quite separate PSUs then always do it at the quiet end. Better still, let each PSU feed its own circuit then connect the signal grounds together.

Yes, this is the royal way.
BTW - I don't understand the circuit completly. Where is the positive rail and the negative rail?
If the neg. rail and GND is the same potential, then electrolytic or foil caps for input, output and NFB definitely imperative.

 

[smithomo]

Yes, this is the royal way.
BTW - I don't understand the circuit completly. Where is the positive rail and the negative rail?
If the neg. rail and GND is the same potential, then electrolytic or foil caps for input, output and NFB definitely imperative.

I did not so much want to talk about + and - rail, the circuit also is not completely draw.
Just want to eye on grounding.

 

[Bensen]

Hi Bensen,
First, you amp look so nice and good circuitry.
Are all cap pins from both channel PSUs are connected to to the same star ground point?
I saw you have 2 separate rectifier boards, so I think it hardly to connect all of them(include diode pins) together to the real single point.
I planned to do it this way for the low power regulated PSU to drives gain stages.
Because of my current mode-VAS is really low PSRR, that the reason why I want to have separation.

Indeed, with separate psu boards, this is not possible. Both psu boards are at the quiet end connected to eachother with a 5mm^2 wire.

 

[smithomo]

Indeed, with separate psu boards, this is not possible. Both psu boards are at the quiet end connected to eachother with a 5mm^2 wire.

I thought you did the great things already, but real star grounding is not easy to implemented practically, especially for a big size component like main cap.

Anyway, what the improvement hum noise when you disconnect both input RCA cables?

 

[gmphadte]

Is the transformer, a toroid or an EI...

Gajanan Phadte

 

[Bensen]

I thought you did the great things already, but real star grounding is not easy to implemented practically, especially for a big size component like main cap.

Anyway, what the improvement hum noise when you disconnect both input RCA cables?

I've just tried: when disconnecting the input rca cables, the level of hum stays the sale, however it sounds different. Anyway, I only hear it when keeping an ear against a speaker.