Splitting ground

Looping and Jacking.

Hi Vuvek,
For correct earth referencing, the input, power supply and speaker grounds should return to a single point (the power supply central ground point) from different directions, being careful to minimise each of these circuit loop areas.
If you have different circuit stages grounded on a common line, the resultant earth jacking can cause additive or subtractive valid signal production - this can cause a transient limiting/foldback characteristic, or a flaring/blapping characteristic according to stage earthing order and behaviour.
Intelligent placing/ordering of these interactive earths can give a desirable envelope response, and give voice to an amplifier system.

Eric.
 

MRehorst

Member
2002-05-17 8:48 pm
Re: Looping and Jacking.

mrfeedback said:
<snip>
If you have different circuit stages grounded on a common line, the resultant earth jacking can cause additive or subtractive valid signal production - this can cause a transient limiting/foldback characteristic, or a flaring/blapping characteristic according to stage earthing order and behaviour.
Intelligent placing/ordering of these interactive earths can give a desirable envelope response, and give voice to an amplifier system.

Eric.

Uh, can you translate any of that to English?

;)

Cheers!

MR
 
hummm

How about - Don't let High current from Speaker Output flow through the same ground ground path used by the control circuitery.

Simply use 2 different ground track on your pcb and connect them via 2 different wire to the capacitor grounding point. One ground for all the High Current and another for the input and signal transistors.

Clearer? :confused:


-Simon
 
Hi,
Thanks to all for your comments but I still do not get it.

"Simply use 2 different ground track on your pcb and connect them via 2 different wire to the capacitor grounding point."

Simon,
Are you saying that the input and driver trans have to be grounded to one point and the input and output terminals will use a different ground track and the two are connected?

Vivek
 
Hi MR,
In years of servicing audio gear I have seen all sorts of dumb wiring and pcb layout arrangements.
This includes doubtful power supply, preamp and power amp supply and grounding layouts, and other errors like taking NFB from an invalid (wrong) point.
I think it is not so much intentional as lacking of knowledge on the designers part.
Some munufacturers do however very deliberately adhere to star grounding of all stages, particularly in modern higher quality shelf systems.
A common error is an inadequate size pcb trace ground common connecting the two main filter caps.
Other errors include grounding stages to the speaker earth return traces.
A close look at the layout and intelligent rerouting and/or beefing up of some pcb traces can yield worthwhile improvement.
Bypassing of main filter caps with additional SMPS electros of around 10% of the main caps is usually a wortwhile improvement also.


Vivek,
Star grounding means that you have a substantial copper area connecting the two main filter caps, and this is the system earth reference to which all stages and input and output connectors are individually connected.
Eric.
 
mrfeedback said:
Hi MR,
In years of servicing audio gear I have seen all sorts of dumb wiring and pcb layout arrangements.
This includes doubtful power supply, preamp and power amp supply and grounding layouts, and other errors like taking NFB from an invalid (wrong) point.
I think it is not so much intentional as lacking of knowledge on the designers part.
Some munufacturers do however very deliberately adhere to star grounding of all stages, particularly in modern higher quality shelf systems.
A common error is an inadequate size pcb trace ground common connecting the two main filter caps.
Other errors include grounding stages to the speaker earth return traces.
A close look at the layout and intelligent rerouting and/or beefing up of some pcb traces can yield worthwhile improvement.
Bypassing of main filter caps with additional SMPS electros of around 10% of the main caps is usually a wortwhile improvement also.


Vivek,
Star grounding means that you have a substantial copper area connecting the two main filter caps, and this is the system earth reference to which all stages and input and output connectors are individually connected.
Eric.

Hi Eric,

I'm glad that whatever you took the other day seems to be wearing off; really thought we lost you there:) ...

On your explanation of star grounding: pulease, no "substantial copper area". You have a, well, star point to where all grounds go. If you use a buss bar on the supply caps, you should make sure that all other grounds connect to it at one point only (the buss bar then becomes the *leads* that connect the supply cap returns to the star point. In fact, the star point doesn't have to be a wire pad on a PCB. It can just be a point where several short traces come together, each trace being connected to a wire (load return, xformer center tap, cap returns etc). Literally a star point. The error you mentioned of inadequate PCB trace size will also be non-existing if you use the star point (it does impair cap performance of course, it is simply adding to the ESR and ESL, but there will not be the effects you mentioned).
It really pays to be *very* meticulous here.

Cheers, Jan Didden
 
Back To Earth

Hi Jan, physical layout constraints dictate that a substantial earth conductor area/volume is required in practice, and experiment confirms this IME.
With perfect star grounding techniques thin conductors are indeed adequate to preserve a non intermodulating signal earth reference and this is fine for low power applications, but IR (and ESR and ESL) losses cause PSRR problems that are typically worse sonically.
Giving for practical purposes an intelligently applied and infinitely conducting (ounces of copper) earth center common point pays substantial dividends in stability and audio clarity of the circuit.

Eric.