Galactic Grounding Techniques

[JonFrum]

I followed Kevin's advice for the most part in my 18 watt build. First, the input and output jacks are isolated from the chassis. Second, the chassis is only connected to signal ground in one place, at the first filter cap. I did not use a ground lift switch here because I don't use effects or connect the amp to any other amp. Third, the safety ground from the cord is wired to a lug right at the IEC socket, and away from the other chassis ground. Forth, each stage of the amp has it's grounds connected to the filter cap of that stage. So the input jack, the preamp cathodes, and the volume and tone pots are grounded at the preamp filter cap. Then, a wire runs between each successive filter cap, from preamp to phase inverter, to output screen, to output plate. As Kevin advises, I have the filter caps on the board with the tube stage components, and I also used radial caps standing up.
So that's what I did, and it appears to work just fine. In my case, the safety ground is connected to the signal chassis ground, but in Kevin's model they can be separated by the ground lift switch. The signal gorund does not have to be connected to the chassis for the amp to work as long as the entire signal chain is connected on the board. My main ground point in the amp is the negative side of the first filter cap, not the chassis. The chassis is only signal grounded to act as a shield to electrical noise from outside.
Another way of thinking of it would be that I have three main ground lugs; the safety lug at the cord connection, the chassis signal ground, which is connected to the board signal ground, and the first filter cap, which is the main signal ground for the transformer. Also, on the board I have secondary ground points at each filter cap, connected in series from power end to preamp end.
I hope that helps.

[JonFrum]

I'll try to do a layout. It's in head form, like Kevin's builds, but I tried to orient the components on the board in line with the tube sockets a little more than Kevin does. Doing the layout was the best part of the project for me - reminds me of being back in school. Which reminds me of all those college girls.

[JonFrum]

Call it a schematic layout. The filter caps are filled in with black. The three filled in circles are 22uF radial caps, the one filled in rectangle is a 32uF axial cap. When the hand drawn lines - not straight - cross lines, they do not connect at that point. Notice that the phase inverter filter cap is the only one that has the negative lead facing the tubes - the others all have the positive side facing the tubes. The chassis ground connections are to the left. The safety ground is on top, and does not connect to the signal circuit. The ground that connects the chassis to the amp circuit is below the safety ground, and connects to the first filter cap. The power transformer center tap is missing, and would also connect at the first filter cap. Where you see one screen resistor for the power section, I actually used one for each tube. The grid resistors for the preamp stage and the power tubes are soldered to the tube socket lugs, as are the power tube screen resistors.
I hope this gives you an idea of what I did. It's the Lite II circuit, with a single preamp tube stage. The power switch and lamp are at the lower left - I left out that wiring, and also the wiring from PT to rectifier. Also, the output jack wiring is missing.
Basically, I just aligned the filter caps with the asssociated tubes, connected them with power resistors between them, and then lined up the rest of the components the most logical way I could. No doubt it still looks more confusing than it really is, but I'm at the limit of my art work.

[s2]

Did you mean to add an attachment? I'm interested in this too, but I don't see a diagram :)

[JonFrum]

Oops! That was a lot of talk about nothing. let's try again.


Edit: I just noticed that there should be a wire connecting the negative lead of the preamp filter cap to the negative lead of the PI filter cap.

[JonFrum]

With correction. It looks like it was drawn with crayons.