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Grounding Question
Grounding Question
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Old 12th March 2019, 11:53 PM   #1
Diyengineer is offline Diyengineer  United States
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Default Grounding Question

Hi,

If Iím doing a sort of a star grounding system located at the input jack, is it ok for cathode resistors and grid leak resistors to share the same wire back to the jack? Or should they have separate wires?

Similarly, is it on for preamp tube cathode resistors and power tube cathode resistors to share the same wire back to the jack as well? Or should those be separate as well?

Thanks
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Old 13th March 2019, 12:04 AM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by Diyengineer View Post
is it ok for cathode resistors and grid leak resistors to share the same wire back to the jack?
is it on for preamp tube cathode resistors and power tube cathode resistors to share
the same wire back to the jack as well?
Think of each stage as a sub-circuit, and run one ground from each stage (grid and cathode).
This especially goes for the output stage, which has larger current and more ripple noise.
But keep all those ground wires short, by good layout. Post some photos.

Last edited by rayma; 13th March 2019 at 12:13 AM.
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Old 13th March 2019, 01:04 AM   #3
Diyengineer is offline Diyengineer  United States
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Great, thank you!
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Old 13th March 2019, 02:42 AM   #4
cerrem is offline cerrem  United States
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Keep in mind there are AC signal loops and DC loops ..... Just remember to keep it short and return it back where it came from... Personally I never use the chassis for current return .... I only ground the chassis in one location for shielding purpose.. The whole concept of using the chassis for return currents was to save on copper wire $$$ and sometimes weight as in some air-frame wiring systems..
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Old 13th March 2019, 08:06 AM   #5
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by Diyengineer View Post
If Iím doing a sort of a star grounding system located at the input jack,
That's not normal. Why are you sending noisy currents back to the input jack??

Quote:
is it ok for cathode resistors and grid leak resistors to share the same wire back to the jack? Or should they have separate wires?
Theoretically they should share the same wire but it's unlikely to make much difference.

Quote:
Similarly, is it on for preamp tube cathode resistors and power tube cathode resistors to share the same wire back to the jack as well? Or should those be separate as well?
Theoretically they should be separate, but if it may not make much difference.
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Old 13th March 2019, 10:24 AM   #6
Diyengineer is offline Diyengineer  United States
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Originally Posted by Merlinb View Post
That's not normal. Why are you sending noisy currents back to the input jack??
I'm am using the jack only because I have read about that method elsewhere. The scheme that I planned to use and have used in a couple other amps I built is the following: I bussed the secondary 0R OPT to the input jack with a 12ga wire. Then tied all P.S. grounds together on the P.S. board and ran 1 wire back to the jack. The P.T. center tap is grounded on the P.S. board at the filter caps. Then tied all of the active circuitry together and ran 1 wire to the jack as well. Then I ran 1 wire from the jack to the IEC ground terminal passing through an X2 cap & low ohm resistor. Then bonded the chassis to the IEC as well. I will separate the active circuitry by stage now, each with a separate run to the central node. If not the jack, where would be the ideal place to locate the central grounding point? And what might the ideal scheme look like? I have read about so many grounding schemes, everyone seems to do it a little different.

Thank you!
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Old 13th March 2019, 12:08 PM   #7
scottjoplin is offline scottjoplin  Wales
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You have confused the star with connecting the amp ground to the chassis at the input socket.
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Old 13th March 2019, 03:03 PM   #8
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by Diyengineer View Post
If not the jack, where would be the ideal place to locate the central grounding point? And what might the ideal scheme look like?
http://valvewizard.co.uk/Grounding.pdf
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Old 13th March 2019, 05:19 PM   #9
cerrem is offline cerrem  United States
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Originally Posted by Merlinb View Post
The input jack is actually a really good place to ground.... This article is very useful for those learning to ground properly... When designing mixed-signal circuitry, a common node for grounding is at the ADC input..
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Old 13th March 2019, 06:25 PM   #10
Diyengineer is offline Diyengineer  United States
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Thanks for the input guys.
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