star grounding a multi-peice cahssis

[llama]

Hi,
I've posted this question at another forum as well, I hope that is not an issue:

I'm building a 5w SE el84 amp head into the enclosure of a 1960’s era voltmeter. I have pics here of what I’m talking about – please see the pics before helping out, because my explanations seems to be lacking in efficiency.

Whole Original unit: https://picasaweb.google.com/1175982181 ... 5962182050
Side view opened: https://picasaweb.google.com/1175982181 ... 1480252066
Mockup of tube layout and OT: https://picasaweb.google.com/1175982181 ... 4374659362
Mockup of main chassis in the enclosure: https://picasaweb.google.com/1175982181 ... 6891279170
More Pics: https://picasaweb.google.com/1175982181 ... tLeU1vCIJg#

I’m just about finished with wiring the terminal boards and am moving to the final connections to the tubes, pots, and such. I am getting ready to design the grounding location(s) to the chassis. All of my components are housed within the main, lower chassis. The pots and inputs will be attached to the face plate that is bolted the main chassis

The PT and the rectifier are located on the upper rectangular over hanging chassis. Wire will be run between the two (B+ , heater and a ground wire). Everything will be screwed/bolted the outer green enclosure.

I’ve read in forums and documents to connect the chassis ground close to the input jack. However, in his book Design and Construction of Tube Guitar Amplifiers, Robert Megantz states to chassis ground by the output jack.

I’m thinking to have one Chassis ground at my mains ground on the upper chassis and have the signal ground at the input jack (actually onto the chassis not the face plate (again see the pics for clarification).

I’m not sure how to proceed. I’m guessing that if I get it wrong the first time, I’ll get a bad hum and then I could correct it.

Any thoughts?

[Structo]

Generally you ground your mains close to where the AC cord comes in.

Since you are basically using two chassis, I would connect the two with a wire to avoid a ground loop.

Ground the filter caps near the power transformer and ground the preamp near the input jack.
That includes any pots that are grounded and of course any cathode bypass on the preamp.

The output generally gets a ground wire from the OT and a mechanical connection at the jack(s).
You can run an additional ground wire to the jack if you get some hum.

Remember, heater hum is 60Hz and power supply hum will be 120Hz so that can help you diagnose any noise and where to look.
Good luck, looks like a cool project.