DIY Audio Projects Forum

I am building a tube audio amp. I am not sure what is the best method to do the grounding. I have taken the mains earth to the chassis to comply with Australian standards. I have also fitted a bus bar for earthing all the components, so that they go back to a central point. My question is this: Should I also ground the "earth bus bar" to the chassis or leave it isolated from the mains earth?

Thanks guys, John

Seperate the signal ground from earth with a pair of front-to-back diodes hefty enough to handle the current if all goes wrong (like 6A8) and bypass them with a 100R, 2W non-inductive resistor.

Cheers!

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-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design

You can also use a resistor and parallel capacitor. The capacitor needs to be a type X2 (ones that are rated for AC mains use) and the resistor ought to be at least 1 watt. Values are typically 120-150 ohms and 0.1 to 0.22 uF (voltage ratings are generally standard at 277RMS). I personally prefer the RC combo as it seems to reduce the noise floor in sensitive gear better but either method will work.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:

• PoddWatt: 5751 / EL84 Push-Pull DIY Tube Amplifier Project
• OddBlocks: KT88 Push-Pull DIY Tube Amplifiers (Mono Blocks)
• ForeWatt: ECC802S (12AU7 / ECC82) DIY Tube Preamplifier Project
• GrooveWatt: Tube (Valve) RIAA Phono Preamplifier Project

OK, Thanks guys for your help.

I have seen Pete Millett use the following:

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Cheers, Alan
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Denon POA 2200 | Bottlehead Quickie with PJCCS | Integra CDC 3.1 | SOTA Sapphire-RG301-Grado Gold 1 | Soundwave Soliloquy Series I

I always thought you filled the chassis with sand.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:

• PoddWatt: 5751 / EL84 Push-Pull DIY Tube Amplifier Project
• OddBlocks: KT88 Push-Pull DIY Tube Amplifiers (Mono Blocks)
• ForeWatt: ECC802S (12AU7 / ECC82) DIY Tube Preamplifier Project
• GrooveWatt: Tube (Valve) RIAA Phono Preamplifier Project

Basically the same, Allan... just sets the voltage at 1.4-2V instead of 0.7-1.1. A handy thing if your ground noise peaks Vp-p are high.

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design

Yes but does the diode type make a difference on the ground breaker should it be soft recovery or a schottky.
Should the capacitor be non inductive..

Just a joke erm.

On a more serious note
The ground of the supply should be earthed so any faults will clear. The ground breaker isn't always necessary I would try it without first (straight to earth) and use it if necessary.
I use different methods of grounding depends what mood I'm in at the time, however I usually star ground the left and right channel then join them together at a common star ground this means I can isolate the grounding independently. The main thing is that under fault conditions no difference in potential appears between any metalwork or between an audio connector and the chassis.
You must never remove the chassis earth to stop hum.

Worst thing I have seen is someone rely on the audio connectors to ground the chassis and when they unplugged the interconnects a voltage appeared between the hand holding the connector and the other hand holding the chassis. The guy was lucky to survive.

Regards
M. Gregg

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What is the sound of one hand clapping?