5F1 Bus Grounding: where to ground speaker out?

[Paul Nordin]

Hi there, I'm on my first built, a 5F1 of course. I'm doing a bus grounding scheme a la Boot Hill's examples I found on the web. Everything seems relatively clear except for two points.

The wiring layout I am using (Triode) has a ground run from the Speaker Jack. Should this go to the power-ground bus or the pre-amp ground bus?

Also, I am installing a 500k pot next to the speaker jack to allow for dialing in a NFB mod. Where should I be grounding this pot?

Thanks!

[robrob]

The black 'ground' wire from the output transformer secondary should be grounded at the speaker jack's sleeve (ground) terminal.

I would ground the variable NFB pot to the preamp bus. That's where the 5F6A Bassman's Presence control is grounded.

[Paul Nordin]

The black 'ground' wire from the output transformer secondary should be grounded at the speaker jack's sleeve (ground) terminal.

I would ground the variable NFB pot to the preamp bus. That's where the 5F6A Bassman's Presence control is grounded.

Thanks. That's very helpful!

[Stevem]

Why such a big value pot to test with, a 15k would be a better starting point in my mind?

[Paul Nordin]

Why such a big value pot to test with, a 15k would be a better starting point in my mind?

I picked that for two reasons, firstly I read a posting from someone else who had used that value Pot for the same mod and really liked the results. So I started out thinking I would just use that. Secondly, that high value allows me for all intents and purposed remove NFB entirely by dialing it up.

I finished the amp this morning and it sounds fantastic, so I feel it was a good choice.

I also ended up taking the Speaker Jack ground back to the PT ground bus. And the amp is pleasantly quite, so all turned out well.

[vibratoking]

Glad you got it working.

[Paul Nordin]

For anyone that might be interested, here is a demo we filmed of the amp.
Cheers

https://youtu.be/BPfQDySbz9o