New Fender "type" amp build suggestions

[foreverstrung]

The NFB can be let on permanently by going from the 4 or 8 ohm tap of the OT and wire it directly to the NFB resistor.

Head scratcher here.
I've got my NFB switch wired just like yours in the pictures you submitted earlier in this thread and exactly as it is in the layout. The noise I was speaking about when this switch is engaged is not normal. It's overwhelming.
The schematic shows a 56K resistor between the switch and the OT rotary switch @ the speaker jack, but the layout and your gut shots don't show this.
I've also got a 22k resistor for the NFB resistor on the turret board (as the layout shows) though the schematic shows a 6.5K......
I hope my description is not confusing. Bottom line is with my NFB switch removed, out of circuit, the amp sounds fine though a tad noisy. Maybe 2 tads noisy. When engaged it's unacceptable. Not playable.
Thoughts?
I'll add a picture though right now I've lifted the lead @ the NFB resistor….. green wire off of NFB switch to rotary switch. Yellow wire (lifted) to the NFB resistor. The jack between the NFB switch and rotary switch is the Vibrato pedal. Yes, I know, the tube sockets are way too close. I’ll definitely lay this out better next time.
Thx
Dave

[Bieworm]

Hold on. Maybe the noise you are pointing towards is oscillation. If so, try to swap the OT primary leads from socket (pin 4)
That is if the noise occurs when the NFB switch is in ON position.
Also.. the 22k on the layout is wrong. It shouldn’t be there. The wire from the switch needs to be connected on the turret where the 6,8k and 1.5k are soldered.

[foreverstrung]

Hold on. Maybe the noise you are pointing towards is oscillation. If so, try to swap the OT primary leads from socket (pin 4)
That is if the noise occurs when the NFB switch is in ON position.
Also.. the 22k on the layout is wrong. It shouldn’t be there. The wire from the switch needs to be connected on the turret where the 6,8k and 1.5k are soldered.

So I removed the 22k resistor and ran the NFB wire directly to the 6k8, 1k5 and .1uF turret.
I also flipped the blue/brown OT wires and the sound is deafening with the NFB switch ON. It's the same sound one gets when you unplug a guitar from a live amp. This is the same sound before I swapped the OT wires......When the switch is ON, it makes this sound. With the switch OFF, the amp sounds pretty darn good. In fact, with both volume knobs cranked and guitar plugged in, the amp is near silent. When I introduce guitar volume, I get the unwanted "grounding hum" like noise I was talking about earlier. It's not present on my other amps but perhaps this amp is just much more sensitive. I can definitely live with it, but the NFB issue is a head scratcher.
Do I just keep it in the off position? I'd hate to just have to "live" with it. I'd always be curious as to what I'm missing and what have I done wrong.
Appreciate your thoughts
Dave

[Bieworm]

You did put the 56k in between the speaker jack and the wire to the 6.8k and 1.5k? Otherwise you get 100% NFB

[foreverstrung]

You did put the 56k in between the speaker jack and the wire to the 6.8k and 1.5k? Otherwise you get 100% NFB

Ok. I’m picking up what you’re putting down. I’ll add that 56k resistor the schematic shows from the NFB switch to the rotary switch. The schematic also shows a 6.5k at the turret board where I just removed the 22k, which would also be on the path to the speaker through the NFB switch. So according to the schematic, that would be 62.5k total out of the NFB signal to the speaker.
I do get what’s going on here better now. I’ll start with the 56k and add more resistance if I need to.
Thx
Dave

[Bieworm]

I don’t see any 6.5k resistor anywhere in the NFB circuit. Do you mean the 6.8k tail resistor of the PI? That has nothing to do with the NFB resistors. You need the 56k from the rotary imp switch to the junction of the PI and the 1.5k to ground.
If ypu want yo play with the level of NFB you can subsitute the 56k for a 100k linear pot and adjust to taste.

[foreverstrung]

I don’t see any 6.5k resistor anywhere in the NFB circuit. Do you mean the 6.8k tail resistor of the PI? That has nothing to do with the NFB resistors. You need the 56k from the rotary imp switch to the junction of the PI and the 1.5k to ground.
If ypu want yo play with the level of NFB you can subsitute the 56k for a 100k linear pot and adjust to taste.

You’re right about that 6.5k. I don’t know where I pulled that out of.
I landed on 82.5k for the missing resistor. I started at 100k, went down to 62.5k. The sweet spot for me was 82.5k.
Thx
Dave

[foreverstrung]

https://youtu.be/1EiKfexPTBI?si=Yy8m4esI1KiKavoh

[Bieworm]

https://youtu.be/1EiKfexPTBI?si=Yy8m4esI1KiKavoh

You did it man!!! It is a really nice amp huh?

[foreverstrung]

You did it man!!! It is a really nice amp huh?

Yes. Very happy with the result. I really appreciate all the input you provided with this project. I am very grateful.
Merry Christmas
Dave

[Bieworm]

You’re welcome. Merry X mas to y’all