Need feedback on this basic grounding schema

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Discussion Overview

The discussion centers around the design and layout of a grounding system for a tube amplifier, focusing on minimizing noise and optimizing component placement. Participants explore various configurations for filter capacitors, grounding techniques, and the implications of different component types.

Discussion Character

  • Technical explanation
  • Experimental/applied
  • Debate/contested

Main Points Raised

  • Billy proposes placing filter capacitors along the high tension (HT) rail, considering both axial and radial types, but notes that radial caps may be too large in diameter.
  • Another participant suggests keeping filter caps close to the HT rectifier to minimize resistance and avoid current spikes along the HT lines.
  • There is a recommendation to place a toroid over the wires feeding the last reservoir capacitor to enhance grounding effectiveness.
  • Billy shares an experimental amp layout that positions filter caps near the rectifier tube, measuring low resistance from the rectifier to the first filter cap, and discusses the grounding connection to a star ground.
  • He notes that while the amp has some hum, it is not excessive, and higher gain and wattage amps present more significant challenges.
  • After changing the input jack ground, Billy reports that the amp is now silent, indicating progress in addressing grounding issues.

Areas of Agreement / Disagreement

Participants express various viewpoints on the optimal placement and type of components for grounding systems, with no consensus reached on a single best approach. Some suggestions are acknowledged as useful, but the discussion remains open to further exploration and refinement.

Contextual Notes

Participants mention specific measurements and configurations, but there are unresolved details regarding the impact of different grounding methods and component types on overall performance.

Planobilly
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Hi guys,

I am trying to find the best way to lay out a grounding system for a typical tube amp.

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I had in mind to place the filter caps along the HT rail. I can use either axial or radial caps. The issue with the radial caps is they tend to be too big in diameter.I am trying to get to some general design for the placement or ground wires/buss. Something that reduce noise to a minimum. Assume AC heaters with twisted wire and perhaps also covered with a braided shield.

Need ideas.

Thanks,

Billy

EDIT: sorry I have the connections to the grids drawn incorrectly. Tip of the input jack goes to V1 Pin 2 and the center of the volume control pot goes to V1 Pin 7
 
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Here is a typical layout and schematic for a typical Fender style amp. Perhaps it will make the drawing above easier to understand.

dyEOfJ1.png


Thanks,

Billy
 
Planobilly said:
I had in mind to place the filter caps along the HT rail. I can use either axial or radial caps. The issue with the radial caps is they tend to be too big in diameter.
Keep the filter caps as close as possible to the HT rectifier. You need minimum resistance between the rectifiers and the caps. You do not want twice mains frequency current spikes traveling along the HT lines.
Place a toroid over the two wires feeding the last reservoir cap. The last cap then provides HT and the ground connection to circuits.
The first cap(s) have the centre tap of HT windings only, no chassis connection except through torroid wires.
 
Thanks Baluncore,
Here is a experimental amp built along the lines of the Bright Switch Mid Pot Layout above. The filter caps in this example are close to the rectifier tube and not along the board. The resistance from the rectifier to the first filter cap measures .03 ohms. As it goes through the standby switch I assume some of the resistance occurs there. The HT ground wire from the transformer is connected to the star ground which you can not see in the video. Directly from the star ground is a wire connected to the negative side of all the filter caps. All these connecting wires are 18 gauge solid copper wire.

Perhaps looking at this video you can give me a better description of what you think I should do.



Thanks,

Billy

EDIT: Just so you know, There is not an excessive amount of hum or hiss in this amp...more than I would like nonetheless. The real problems occur as the amps have higher gain and higher wattage.
This one is only 20 watts or less.
 
With a change to the input jack ground the amp is dead silent now. On to the high gain amp next.

Thanks for all the ideas and links as they were very useful. I think I am starting to get a handle on the grounding issues.

Cheers,

Billy