Multiple components. Best ground design?

[Alexontherocks]

I really could not find anything really useful.

Here is my build:



and here is the top layer (dc protect and preamp)



All the amps have a ground faston. I usually wire the output from there to the DC protect modules and over to the speaker output connectors. From there I wire the outputs directly to a central ground.

I understand my approach is totally worng, but what should I do?
Thinking of best ground I imagined 2 ground star centers. One for the power amps and one from the preamp which then merge at the socket ground.

Is this correct?

a picture of two alternatives I thought of regarding ground:

1. starground (for the poweramps)


2. non-starground (for the poweramps)


I am really lost....Could someone please sketch with paint over my intial photograph a good design for ground? In the picture with the top layer all the modules are present.

Thanks
Alex

[richie00boy]

Yes the way you did it first was bad. Grounding should be simple and I'm not sure why people get so confused over it.

The master ground reference is at the centre of the big PSU caps. Any boards or loads should have their ground wire back to that point and that point only. The mains ground socket pin should also wire to that point. If your amp boards have a speaker ground terminal, ignore it and wire back to the star point. Unless its a UcD amp.

Input leads to your amp should use screened cable and use the input ground terminal on the board, not back to the star.

Your DC protection module will need a ground just for reference, take this from the star.

[Alexontherocks]

Thanks! So star is ok...

couple of other questions:

1. best way to gound black output terminals?
2. Should I connect the preamp ground to another star or connect it directly to the socket AC?
3. chassis is connected to star ground or to socket ground?

[jcx]

"best" is hard to say in multichannel chassis - signal grounds are likely shorted together at the source, preamp card, this makes it hard to avoid loops, common impedance pickup

power gnd distribution shouldn't be considered independent of power distribution as your "star" sketch shows – bundling each amp's pwr gnd return with its own pwr wires reduces radiating loop area

practical "good" is to have gnd loop isolation/breaking in the system - such as differential receivers at the amp boards - sometimes can be done with just a few R tacked on

I would consider reversing/flipping the power caps end for end - where are the rectifiers? - you want the xfmr, pwr diode, pwr reservoir C wiring to be as small in loop area as possible

close packing of all the pieces, planar orientation doesn't help either

[digits]

Originally Posted by richie00boy

Yes the way you did it first was bad. Grounding should be simple and I'm not sure why people get so confused over it.

The master ground reference is at the centre of the big PSU caps. Any boards or loads should have their ground wire back to that point and that point only. The mains ground socket pin should also wire to that point. If your amp boards have a speaker ground terminal, ignore it and wire back to the star point. Unless its a UcD amp.

Input leads to your amp should use screened cable and use the input ground terminal on the board, not back to the star.

Your DC protection module will need a ground just for reference, take this from the star.

I agree with this, I don't even put GND out on my amp boards any more.

[Alexontherocks]

Originally Posted by jcx

"best" is hard to say in multichannel chassis - signal grounds are likely shorted together at the source, preamp card, this makes it hard to avoid loops, common impedance pickup

power gnd distribution shouldn't be considered independent of power distribution as your "star" sketch shows – bundling each amp's pwr gnd return with its own pwr wires reduces radiating loop area

practical "good" is to have gnd loop isolation/breaking in the system - such as differential receivers at the amp boards - sometimes can be done with just a few R tacked on

I would consider reversing/flipping the power caps end for end - where are the rectifiers? - you want the xfmr, pwr diode, pwr reservoir C wiring to be as small in loop area as possible

close packing of all the pieces, planar orientation doesn't help either

the rectifiers are between the black caps and the toroid soldered on the board.

Unfortunately the layout was not a free choice as the space is little and the casings cost a fortune!

I have also created these:


basically two diodes soldered opposite one another with a 100ohm resistor in parallel. Simple ground loop breakers.

Can the be effectively used in my design in critical spots?

Also this is half the ground star design completed:



the connectors will then be wired to the socket ground.

Also the central connector is wired to the caps board underneath.

Here is a picture of the upper layer with the DC modules hooked up to a reference ground wire which will be connected to the socket on the back panel.

[jitter]

I'd like to point out that there's a good article about grounding on diyAudio: Audio Component Grounding and Interconnection. Especially chapter 4 is relevant to this thread.

[Alexontherocks]

Originally Posted by jcx

"best" is hard to say in multichannel chassis - signal grounds are likely shorted together at the source, preamp card, this makes it hard to avoid loops, common impedance pickup

power gnd distribution shouldn't be considered independent of power distribution as your "star" sketch shows – bundling each amp's pwr gnd return with its own pwr wires reduces radiating loop area

practical "good" is to have gnd loop isolation/breaking in the system - such as differential receivers at the amp boards - sometimes can be done with just a few R tacked on

I would consider reversing/flipping the power caps end for end - where are the rectifiers? - you want the xfmr, pwr diode, pwr reservoir C wiring to be as small in loop area as possible

close packing of all the pieces, planar orientation doesn't help either

the rectifiers are between the black caps and the toroid soldered on the board.

Unfortunately the layout was not a free choice as the space is little and the casings cost a fortune!

I have also created these:


basically two diodes soldered opposite one another with a 100ohm resistor in parallel. Simple ground loop breakers.

Can the be effectively used in my design in critical spots?

Also this is half the ground star design completed:



the connectors will then be wired to the socket ground.

Also the central connector is wired to the caps board underneath.

Here is a picture of the upper layer with the DC modules hooked up to a reference ground wire which will be connected to the socket on the back panel.

[jcx]

you may have to try several of the suggestions to get to "good enough" - measurements are important to keep you moving in the right direction

a even motherboard PC sound chipset should enable measuring gnd impedance signal coupling to ~ -80 dBV

pro instruments, bench multimeters with ACV response to beyond 1kHz, Oscilloscope are pretty necessary



strictly speaking green/yellow should only be used for Protective Earth/Safety Ground - not as functional gnd carrying current in normal operation

inside a amp chassis it would only be used between the IEC socket Earth Ground pin, chassis gnd and the star point

not a big problem if not going to be officially inspected or sold to the unsuspecting

[richie00boy]

Originally Posted by Alexontherocks

Thanks! So star is ok...

couple of other questions:

1. best way to gound black output terminals?
2. Should I connect the preamp ground to another star or connect it directly to the socket AC?
3. chassis is connected to star ground or to socket ground?

1. I already told you, speaker ground to star.
2. If the pre-amp is in the same box use the star. Do not link grounds between the two boards by the signal cable - the signal cable should either be a single wire connecting signal only, or a screened cable with the screen terminated at only the amp input end.
3. Socket ground should have a short thick wire to the enclosure and be attached to a bare metal point via a shakeproof washer. This bolt should not be used for any other purpose, not even mechanical or electrical. The star should connect to the socket ground.