• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Grounding & board Layout questions

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Hi,

I know that the grid resistors for the output tubes should be mounted directly on the socket. But what are the other components that should also be soldered off the board i.e. on sockets etc.
I read somewhere that grid leak resistors should be soldered to the socket, what is a grid leak resistor & how can locate it on the schematic?

I’ve been told that PS’s filter caps. As well as some other components (like output cathode caps.) Should be earthed directly to the star-point i.e. not to the boards ground wire to avoid ground loops. Is that true?

What should be a sufficient thickness for the ground wire?
 
The grid stopper resistors (the series resistor to the input grid) of any tube should be mounted such that the resistor body is right up against the socket pin. They are the only "critical" resistors which need that. Note that for pentodes there will also be g2 stopper resistors and these should be mounted the same way - with the resistor body right against the socket pin. g2 stoppers are particularly important for the output tubes in Ultralinear Amps.

The grid leak resistors are the resistors which come from the other side (away from the socket) of the grid stopper resistors and wire back to either 0V or the bias supply. It doesn't matter where these grid leak resistors are.

Cheers,
Ian
 
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