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-   -   Pre-amplifier grounding compendium? (http://www.diyaudio.com/forums/solid-state/211182-pre-amplifier-grounding-compendium.html)

gentlevoice 20th April 2012 02:47 PM

Pre-amplifier grounding compendium?
 
Hey Diy'ers,

I'm in the process of making a preamplifier and wonder if any of you knows of a thread here in DIYaudio - or elsewhere - that can be considered a "compendium" on the best routing & grounding strategies for pre-amplifiers?

I know of this article by Guido Tent of Tentlabs:

http://tentlabs.com/Components/Shunt...decoupling.pdf

- which is about supply decoupling and tracing in that respect, but is it e.g. wisest to place the common ground close to the input or close to the output? And what would be the reasoning for either choice?

So if any of you knows of a short, easy-to-read, yet valid "compendium" on grounding I'd appreciate hearing about it.

Spring greetings from Denmark,

Jesper

Mooly 20th April 2012 05:19 PM

I don't know of or indeed haven't seen a compendium on this.

Every design is unique and every design MUST follow basic principles. It helps to think of it all as a DC problem sometimes. Ask yourself, "if any current were to flow in this line or that track etc, then will it alter the output of the circuit in way".

To just follow the "star ground" and connect everything to that approach doesn't work in practice... there are just to many ifs and buts.

If you can read all of this then it might give you a little insight into the problems.
http://www.diyaudio.com/forums/solid...-tappings.html

hags 20th April 2012 07:08 PM

If working on a preamp with a 2 layer pcb why not dedicate one layer for power/decoupling traces and grounds and the other for signal routing and signal ground.

Use a ground plane on each layer and then have them connect at one point/via on the board for connction to the PSU.

I have seen Borbely use this approach, although he did not use ground planes but simple traces due to the single layer.

jcx 20th April 2012 07:28 PM

I won't even try to do 16+ bit resolution instrumentation circuit designs for anybody not willing to spring for 4 layer PCB - at low production volumes it is a waste of time and money trying to squeeze the performance into 2 -layer layouts - requires more design time, often more pcb layout/prototype passes

for pre-amp level signals a single gnd plane is likely OK, possible slots/necking down to constrain power supply/return current paths

the bigger issue can be deciding what to do with source signal gnd, chassis, safety gnd, gnd loops from PS leakage currents

Whitlock's papers at the Jensen site is good for the system interconnect issues - even if he keeps ending up recommending signal isolation transformers http://www.jensen-transformers.com/apps_wp.html


there is also an article here at diyAudio: http://www.diyaudio.com/forums/diyau...onnection.html

hags 20th April 2012 07:39 PM

Quote:

Originally Posted by jcx (Post 2993899)
I won't even try to do 16+ bit resolution instrumentation circuit designs for anybody not willing to spring for 4 layer PCB - at low production volumes it is a waste of time and money trying to squeeze the performance into 2 -layer layouts - requires more design time, often more pcb layout/prototype passes

for pre-amp level signals a single gnd plane is likely OK, possible slots/necking down to constrain power supply/return current paths

the bigger issue can be deciding what to do with source signal gnd, chassis, safety gnd, gnd loops from PS leakage currents

Whitlock's papers at the Jensen site is good for the system interconnect issues - even if he keeps ending up recommending signal isolation transformers JENSEN TRANSFORMERS, INC. - APPLICATION PAPERS AND SCHEMATICS


there is also an article here at diyAudio: http://www.diyaudio.com/forums/diyau...onnection.html

Right, so it's more difficult, but possible, but at the same time not important b/c it's likely ok. :confused:

At low, DIY volume, say one or two boards for personal use, 4 layer boards are cost prohibitive for a hobbyist such as myself.

I don't see anything wrong with a 2 layer, 2 ground plane approach for diy. No iso. transformers please.

jcx 20th April 2012 08:15 PM

if you don't insist on "professional" look - all signals routed on board, no jumpers, no bus bars, no aux boards then you don't have to go 4-layer if you don't have mixed signal MHz DSP, uC, ADC, DAC on board

imaginative use of jumpers, twisted pair pwr distribution, all Class A, low current circuitry you can do OK on a nominally 2-layer board - too many diyers try to make their board layout look "pro"/mass producable not understanding the effort, compromises that went into those layouts

in fact you can do really well on gnd plane perf board for one-off circuits if you let actual electrical performance demands guide your build instead of tyring for a "pro look"

read everything Jim Williams has written on prototyping, layout - Pease was OK for audio frequency signals

Antoinel 20th April 2012 08:37 PM

Kent English of Passlabs has an article entitled "Ground loops" which helps.

hags 20th April 2012 09:10 PM

Quote:

Originally Posted by jcx (Post 2993977)
if you don't insist on "professional" look - all signals routed on board, no jumpers, no bus bars, no aux boards then you don't have to go 4-layer if you don't have mixed signal MHz DSP, uC, ADC, DAC on board

imaginative use of jumpers, twisted pair pwr distribution, all Class A, low current circuitry you can do OK on a nominally 2-layer board - too many diyers try to make their board layout look "pro"/mass producable not understanding the effort, compromises that went into those layouts

in fact you can do really well on gnd plane perf board for one-off circuits if you let actual electrical performance demands guide your build instead of tyring for a "pro look"

read everything Jim Williams has written on prototyping, layout - Pease was OK for audio frequency signals

I'll have to look up your recommendations.

Ha, no more perf-board please! I've used them for years with great success but have recently started using layout software, Eagle and ExpressPCB. Much nicer IMO.

gentlevoice 21st April 2012 06:03 PM

Hey All,

& thanks so much for your replies ;)

I've taken a look at your comments and your links and I can see that there's a bit of reading to do - and things to ponder - so will say thanks for now, and start reading/pondering ;)

'Best for your day (evening it is here in Denmark),

Jesper

djoffe 21st April 2012 08:52 PM

Doug Self has lots of good things to say about this in his books.

Here's an article I wrote for my web-site:

http://www.updatemydynaco.com/docume...lemsRev1p4.pdf

All the best...

Update My Dynaco


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