Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: apeontheweb on February 10, 2026, 01:16:54 pm
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When I built my 5E3, I wasn't 100% sure what grounds to keep together and which to keep apart. This is what I did. (The power transformer has 4 mounting bolts and I used these bolts for most of my grounds.) Any advice or comments are welcome:
Ground wire from 3 prong wall grounded at PT mounting bolt 1
Ground wire from tone, volume pots, filter caps grounded at PT mounting bolt 3
Ground wire from PT secondary 6.35 VAC (the heater tap) grounded at PT mounting bolt 4
Ground wire from PT secondary 340 VAC (the 5Y3 tap) grounded at PT mounting bolt 4
Valve 1's cathode bias (res and cap) grounded at soldered ground point on chassis opposite end from PT
Input jacks are grounded through their body to chassis. (This seems maybe wrong?)
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Lots of threads and instructions on this here, but quick points on what i do - not sayin its the only way - just what works for me.
I do not like to use PT mounting bolts. I drill holes and use soldered grounding lugs.
One for the power cord ground only.
One near the PT for the center taps and the power tube cathodes and the power section filter caps.
One near the input jacks for all the preamp grounds, including any preamp filter caps.
I use toothed washers on the input jacks and crank them firm. If the preamps ground is very close I sometimes run a ground wire from the input jacks to that ground. Many might argue that if doing this the input jacks should be isolated from the chassis. I have not found that necessary, but I do not build high gain amps.
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Do not use the PT bolts, can't trust them, they will get loose. Bolt through the chassis like bmccowan said.
Read the link below on grounding from fellow member Merlin. Use the bussed local star grounding.
Pays special attention to how he shows to ground the 1st B+ filter cap and PT B+ CT in Fig. 14.11b. It looks like a very small change but it can/does/will have a very large reduction in ground humm.
That ground connection has the most current draw in the amp so, so has the most ripple from charging of that 1st filter cap. Fig. 14.11b isolates that cap/PT CT into their own little loop.
On a 5E3, you can use 2 chassis grounds, 1 for the power amp chassis ground near the PT end away from the preamp chassis ground, 2 for all the rest/preamp. Most guys just use the input jack ground as it's bolted to the chassis.
https://www.valvewizard.co.uk/Grounding.pdf (https://www.valvewizard.co.uk/Grounding.pdf)
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Thanks for the responses. This article you linked doesn't leave any stones unturned. I'll spend some time with it.
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What others have said
Mains earth ground should be via its own dedicated secure chassis connection.
'Secure' means a ring terminal secured with a mechanical locking nut and bolt.
The earth wire inside the chassis should be stranded wire and this should be firmly clamped to the ring terminal so the wire won't slip out of the terminal clamp before soldering anything. This is so as to provide a secure mechanical connection.