Smallbox NFB move question?

Purpleibby

Active member
This is the easiest way to do it. Just use the nut/ washer from output jack. You’ll need a couple extra washers to space the switch on back side.

Cut the threads of the nut off to make a washer out of the nut. Use the spacers between switch and chassis. Install nut/washer on front side and use the nut that came with the switch to secure it.

To hide the switch inside the jack and recessed like in the picture of my 69’ I posted requires cutting the entire jack and using epoxy to secure the switch.


HJqJRkSl.jpg


TA6etJ0l.jpg


nlqjejyl.jpg


iuWYhLJl.jpg
Nice! WTF are you cutting that nut with? Some great ideas there and an elegant solution.
 

Purpleibby

Active member
I just used a mini hacksaw. The Cliff nuts are metal but can be cut pretty easily.
Everything turned out great, thanks. Just came up with another solution for mounting it...the insulator from the cliff jack and the wide dress nut(along with a nylon/lock washer/bolts) did the trick for mounting it securely. Tried to get parts that would match the build(caps/pot/switch/wire)
IMG_5871.JPG
IMG_5873.JPG
IMG_5864.JPG
 
Last edited:

Purpleibby

Active member
OMG what a difference that made.....First, let me talk about the NFB mod(4 ohm tap)

With this, this is really what I envisioned what the BE100 should sound like when I first got it. Man I don't have to crank the treble and presence as much now(which made it spikey before, and constantly tweaking the controls between not enough cut/ice pick and balance with the low end)... Now I can have my treble/presence at 5(or a little bit above) and everything is more balanced/clear/open...the lows have tightened up and "feel" right. More punch. It really feels like you're fighting the amp a LOT less, and it was already a good feeling amp...but by no means is it thinner in tone IMO. Clarity without having the ice pick to get it. My God I just couldn't stop playing it, the FEEL is so much better(it was already great feeling but, still it's a massive difference what this did to the amp, wow).

The Death(Depth) control and frequency switch(normal, JJ) really work so well....it's perfect as I can dial in the low end better(I STILL leave the preamp bass cranked and adjust the depth to taste/valume level). TBH I was a little worried I bought the wrong taper pot as I got a 1M linear, but looking around I think I made the right choice for the depth pot....and it works great. Stuck with the mallory caps like the amp has....

I was going to use the original .0047 Mallory cap that was in the resonance circuit....I bought a new Mallory .0047 and tested it against the res cap in the amp...the value of the cap in the amp was around .0044 - .0045...the new Mallory cap was .0047 - .0049(both within tolerance)...I decided just to use the new mallorys I bought and I'll keep the OG parts.

I am so happy. This is all this amp really needed for me. I need no other mods, I love the character of this amp.
 

RedPlated

Well-known member
I agree 100% on the NFB tap. I have an original two input BE100 that was originally on 16 ohm tap. Just going to the 4 ohm tap helps a lot. That version BE100 also has a 100pf fizz cap at the PI. I changed that out to 68pf and it opens it up even more. Sharper attack, less roundness on low strings.

A linear 1M can work great for depth. But a linear at 9 o clock, or only 1/4 of the way up is about the same as a 1MA at 2 o clock. It just comes on much much faster. The pot does the same thing overall but at a much different taper. Audio does give more "control" over the range in my opinion.

I dislike film caps for depth circuits. Cheap 30 cent ceramic disks have been the best sounding depth caps for me. Valvestorm sells them and they're great.

If you really want some tweakability, install a100kL pot with a 22k NFB resistor for variable NFB. Extremely useful.
 

Purpleibby

Active member
I agree 100% on the NFB tap. I have an original two input BE100 that was originally on 16 ohm tap. Just going to the 4 ohm tap helps a lot. That version BE100 also has a 100pf fizz cap at the PI. I changed that out to 68pf and it opens it up even more. Sharper attack, less roundness on low strings.

A linear 1M can work great for depth. But a linear at 9 o clock, or only 1/4 of the way up is about the same as a 1MA at 2 o clock. It just comes on much much faster. The pot does the same thing overall but at a much different taper. Audio does give more "control" over the range in my opinion.

I dislike film caps for depth circuits. Cheap 30 cent ceramic disks have been the best sounding depth caps for me. Valvestorm sells them and they're great.

If you really want some tweakability, install a100kL pot with a 22k NFB resistor for variable NFB. Extremely useful.
Right on. Thanks, about the caps...I just wanted to keep the vibe of the amp how Dave had it, it will be cool to try that sometime. It did seem like the linear had more gradual at the top of the range, and faster at the bottom...which I guess would be the opposite for audio...depends on which range you want more gradual control over. I liked it at about 1 oclock but I'm still getting to know it:)
 

Luke Gibson

New member
Well, I finally got around to modding my Smallbox, only moved the negative feedback to the 4 ohm tap and have to say it made a remarkable difference in my amp. Feels better under my fingers and definitely a little more open sounding. Honestly don’t want to replace the caps because I’m afraid to mess up the way it’s sounding now!
 

Purpleibby

Active member
Coming back to this....man this amp is at another level for me now. It needs the Depth control IMO. I was thinking well damnit maybe I'll try an audio taper as it's easy now to change it out....but after using it even more....I want that gradual range at the top/middle of the pot rather than at the beginning of the range where I'll never use it. Linear taper stays. Now I'm putting my presence at around 12 oclock and the treble at just under 6 or 5 1/2(in that range)....bright with not too much snarl when playing the high notes on the high E with the bridge pickup. The string noise is balanced better that way too. Bass cranked, Mids 3 1/2, depth a hair past noon. Man, desert island amp now. Gave new life to the clean channel too(nfb mod)....but I think of that channel on this amp as an od pedal channel as it seems to work GREAT for drives! Nothing is going to top my Mesa Studio Pre for cleans(that's my clean channel)
The cab: Suhr/CAA 4x12 when he was doing 60 Marshall style with dovetails.
 

Attachments

  • 39161834850_c927bf7336_b.jpg
    39161834850_c927bf7336_b.jpg
    158.9 KB · Views: 2
Top