Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: W5FH on April 27, 2023, 07:22:07 pm
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I wanted to ask about the best way to ground the shield that is between the triode sections of tubes like the 6N2P. The tubes I have appear very similar, the TungSol TS-272. The shield is connected to pin #9. I measured 2.8 pF between pin #9 and either of the plate pins. So, it appears there will be a tiny amount of audio signal coupled to the shield. My question is which is the best way to ground the shield? I wire my amps using the single ground bus method with one continuous heavy guage bus wire starting at power supply and ending at input jacks. If I just connect the shields to the chassis could I be setting myself up for a ground loop issue? Or, should I connect the shields to the ground bus wire?
I am going to be experimenting with the TS-272 in place of 12AX7 in preamp.
Thanks all.
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2.8pF? Just ignore that. How did you even measure that?
I would put a ground lug under the socket nut/screw that's close to pin 9. Then just a short bare wire from pin 9 to the ground lug.
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OK Steve-
I have a capacitance meter that I use. I check every capacitor with it before putting into amp during builds. Thought I would measure the capacitance between shield and plates. I realize that stray coupling in wiring can reach similar values. Just being cautious. My initial thought was just as you state, just ground the shield at socket mounting screw. Thanks.