Brass ground plate necessary?

[spicoli]

Hi, what is the purpose of the brass ground plate under the pots and jacks of a tweed amp, and is it necessary? I did not use one when I built a 5F1 and it is a quiet, great sounding amp. Now I'm building a 5E3 - what are the drawbacks of just grounding to the chassis?

Thanks.

[Bruce / Mission Amps]

It is not critical but it does make grounding the input jacks with respect to the tone/volume pots and the preamp stage cathode resistors.

[spicoli]

Can this be accomplished with a copper wire ground bus from the pa cathode resistors to the jacks and pots?

[tubeswell]

Can this be accomplished with a copper wire ground bus from the pa cathode resistors to the jacks and pots?

That's what I did when I built my 5F2A - wired everything (including cathode resistors and pre-amp filter cap) to a terminal post and had one wire going from that to the input socket ground lug.

The output cathode and the output filter caps went to the other ground (along with all the PT center-taps, the mains ground, and the PT shield). This amp doesn't have any ground hum problems

[Bruce / Mission Amps]

Can this be accomplished with a copper wire ground bus from the pa cathode resistors to the jacks and pots?

Well, some very successful builders just use a solid piece of grounding "bus wire" soldered to the backs of the pots and use that instead of the brass plate. That works fine if it used as a form of a main star ground.
The brass plate is actually like a very large, low impedance star ground.
If everything is grounded to it, it doesn't really matter much if the brass plate is grounded to the chassis that well... but with such a large surface area, it is anyhow.