Grounding multiple channels.

[Captain chunkulus]

So, I know this is been covered at nauseam. Grounding has been covered over and over and over and over again. But I'm curious, how would you guys go about grounding three separate channels of tone stacks with gain and volume in a  tube preamp? I've seen people do a ground through the lugs of the pots, straight wire across the back of the pot casing with the ground lugs tied to the pot casing, wires directly from the lugs to the cathode resistors or tied to a turret board bus then grounded at the input jack. With three separate channels, I'm wondering what the best way to skin this cat is. In other words do I run a bus wire across all three sets of EQ and tie it to the input jack and then tie the ground lugs to the bus wire that's soldered to the backs of the pot casings? Having three tone stacks, gain pots and volume for each Channel, do I will run one single bus wire across all 15 pots? Just a little perplexed at what the best way to ground the pots are. Just looking for some advice from one of you guys and how you might do this. Thanks.

[sluckey]

Should be no different than a single channel or two channel preamp. But don't solder anything to the back of the pots! Instead, float the ground buss behind the pots. BTW, your pic shows some very poor solder joints on the backs of the pots. If this is the previous carcass you are rebuilding I suspect this quality of soldering is a major contributing factor in the failure of your previous project.

Here's how I install a pot buss...

     http://sluckeyamps.com/phoenix/p11_big.jpg

[Captain chunkulus]

Yeah it's a rebuild. I plan on working on the soldering stuff and making it better. I have lyme disease so my hands tremble these days. Makes it much harder to do things  but I'm going to try to make it better.

[dude]

Sluckey, that bias locking pot on your Phoenix, where can I get them in values like 50KA, 25KA, 10KA. Lot of my amps have the 1 ohms resistors lugs on the open back, bias pots I put in a better location outside the amp but they always seem to get moved somehow....?

[sluckey]

Sluckey, that bias locking pot on your Phoenix, where can I get them

Look for Vishay PE30 pots at Mouser. Look closely. Not all have the locking nut/bushing. Mine came from a decommissioned radar site.

[DummyLoad]

https://www.elliottelectronicsupply.com/potentiometers/rv6-series-1-8-shaft.html?arrow=1&dir=desc&limit=all&order=price

--pete

[sluckey]

Hey, those are even priced right! Thanks for that link.

[dude]

I called about the locking pots, takes 5/16” hole, threaded part is about 1/2”, total length is a little over an inch not counting tabs. Width is about 5/8”. One full turn, seems perfect for external bias pot. Second on the thank you

[sluckey]

Kinda like this...

     http://sluckeyamps.com/6v6plexi/P-6V6_05_big.jpg

...or this...

http://sluckeyamps.com/sunn/mod_1.jpg
http://sluckeyamps.com/sunn/mod_2.jpg

[shooter]

Looked at your site DL, nice selections, good geek stuff 

[dude]

I was sawing the shaft off a 1/16” from the threads, putting a slot on the cut end, installing on back of amp. From putting spk jacks, turning spk switch or whatever the bias was often off. I often thought setting the bias without knowing the plate voltage wasn’t as accurate...? But probably not that critical, although when changing rectifier tubes too, there can be a big difference in plate voltage. But l would think setting up a way to check the plate voltage externally would be unsafe..? Getting a little anal l guess, 

[PRR]

> setting up a way to check the plate voltage externally would be unsafe..?

[dude]

4 volts a lot better then 400v, (ex. 375dc plate voltage at socket, at test point 3.75dc) probably over-kill but nice to know it can be done safely, thanks.