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Old 11th October 2012, 01:29 PM   #11
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Ahh! Yes, those loops. In my layout, I plan on using the star ground approach for its commended benefits. But by what you are mentioning in size of the loop, smaller is better right? My initial thoughts with that was spacing components out a bit will help keep each others magnetic fields away from each other. But this method possibly suggests otherwise.

So for external EMI, a tighter packed star ground system is wiser for smaller loops. But with internal EMI from things such as heater lines and transformers, it's wiser to give some room. So is external EMI worse than internal EMI?
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Old 11th October 2012, 03:40 PM   #12
marce is offline marce  United Kingdom
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Actually a ground plane is better for EMI for small signal stuff, just seperate high current ground returns. So for a pre-amp you,d be better with a ground plane and circuitry close together to minimise trace lengths. You would also get better signal integrity, and a copper pouraround all your signals and ciruitry will shield signals from each other and reduce cross talk. sing a ground plane helps minimise loop areas.
The attached PDF shows size reduction taken to the extreme, the larger devices are a standard 8 pin DIP and a 8 pin SOIC.
Attached Files
File Type: pdf compare.pdf (78.8 KB, 17 views)
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Old 11th October 2012, 06:22 PM   #13
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No way! Im so used to hearing how star-ground setups are the do all new default standard. The ground to chassis being acoustically 'difficult'. But interesting with the smaller pre-amp ground-plane concept. Cross talk was my fear. If I can manage getting star grounds in such a tiny setup, with the addition of a copper chassis (cage), shouldn't that be just as good even at that scale? (although slightly more costly)
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Old 12th October 2012, 04:41 AM   #14
qusp is offline qusp  Australia
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no it shouldnt. star grounding is all well and good and worked well for its time (its hardly a new default standard, its just taken some a while to catch up), but I dont believe it beats a ground plane in a low noise, small signal design
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Old 14th October 2012, 08:16 AM   #15
marce is offline marce  United Kingdom
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On every low level analogue board (this includes audio) I have worked on has been either multilayer with a full ground plane or were cost outwayed quality a two layer board with most of the routes on the top and the bottom layer a near as contigous ground plane as possible.
The star ground actually comes from a star ground point where you dont want high and low current signals mixing and causing problems.
The spider legs 'star grounds' only apear on DIY audio sites, and have taken the star point to the extreme. They are not the best choice by a long way, not only adding extra parasitics, but no use for EMI suppression and worse for signal integrity.
AA quick link:
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
And further info including links to a lot of EMC related design notes and information by Keith Armstrong is nincluded in the text file attached.
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File Type: txt PCB related links.txt (5.0 KB, 4 views)
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Old 14th October 2012, 09:53 AM   #16
qusp is offline qusp  Australia
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yeah, I was referring to the latter spiders web stuff which is the most common meaning here.
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Old 14th October 2012, 10:20 AM   #17
marce is offline marce  United Kingdom
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I have nightmares about them, hundred of spidery grounds coming to get me in the night for being against them
Eight Legged Freaks - Wikipedia, the free encyclopedia
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Old 14th October 2012, 12:07 PM   #18
DF96 is offline DF96  England
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Blindly applying any grounding scheme can lead to tears before bedtime. At present, as it is the most popular, 'star ground' is probably the one most often used badly.
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