Question about Star Grounding

voivodata · 20th March 2007, 12:39 PM

Hi

Some articles suggest that generally it is better to keep local audio grounds separate from the local PS filtering caps’ grounds. Others suggest that the local star ground of a given stage is the place to connect the ground lead (as short as possible) of the PS filtering cap used for that particular stage.

So,... I’m building a guitar preamp with four stages of 12AX7. The B+ of each stage will be decoupled from the consequtive stage with a 2K7 resistor and a 22uF filtering cap. Each stage will have a Local star ground where the stage’s grid resistor, cathode resistor and bypass cap will be connected. The problem is that I’m not sure which is better:

(1) to run the ground lead of each of the 22uF filtering caps directly to the Main star ground (which will be the place where all the Local star grounds and the ground lead of a big 220uF PS filtering cap will be connected), or

(2)to connect the ground lead (as short as possible) of each of the 22uF filtering caps to its "corresponding" Local star ground, which will then be run to the Main star ground?

My priority is to avoid noise (ground loop or other).

Have you any thoughts?

Thanks! V.

SY · 20th March 2007, 01:28 PM

Go to www.aikenamps.com and hit the Tech Info button. Then "Advanced," then "Star Grounding."

richwalters · 20th March 2007, 07:46 PM

For those who build power amps (like myself) with pfc circuitry the only way I can get all the noise and cra_p down with good S/N ratio is use massive chassis material (Ally)and earth directly on it as short as possible wherever one can. The old philosophy of an isolated earth loop and earthing on input socket to chassis won't work for min EMI unless filtering is by luck perfect....an RF hint for those who want to use SS power supplies in power amps.

richj

20th March 2007, 12:39 PM	#1
voivodata diyAudio Member Join Date: Apr 2006 Location: Utica	Question about Star Grounding Hi Some articles suggest that generally it is better to keep local audio grounds separate from the local PS filtering caps’ grounds. Others suggest that the local star ground of a given stage is the place to connect the ground lead (as short as possible) of the PS filtering cap used for that particular stage. So,... I’m building a guitar preamp with four stages of 12AX7. The B+ of each stage will be decoupled from the consequtive stage with a 2K7 resistor and a 22uF filtering cap. Each stage will have a Local star ground where the stage’s grid resistor, cathode resistor and bypass cap will be connected. The problem is that I’m not sure which is better: (1) to run the ground lead of each of the 22uF filtering caps directly to the Main star ground (which will be the place where all the Local star grounds and the ground lead of a big 220uF PS filtering cap will be connected), or (2)to connect the ground lead (as short as possible) of each of the 22uF filtering caps to its "corresponding" Local star ground, which will then be run to the Main star ground? My priority is to avoid noise (ground loop or other). Have you any thoughts? Thanks! V.

20th March 2007, 01:28 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Go to www.aikenamps.com and hit the Tech Info button. Then "Advanced," then "Star Grounding." __________________ If there's a sucker born every minute, where do the rest of them come from?

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20th March 2007, 07:46 PM	#3
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	For those who build power amps (like myself) with pfc circuitry the only way I can get all the noise and cra_p down with good S/N ratio is use massive chassis material (Ally)and earth directly on it as short as possible wherever one can. The old philosophy of an isolated earth loop and earthing on input socket to chassis won't work for min EMI unless filtering is by luck perfect....an RF hint for those who want to use SS power supplies in power amps. richj