Dumble-ish Bandmaster Mod Ideas

[overlandltd]

O great knowers of Dumble, I come to your temple seeking guidance.

I scored a mid-60s Bandmaster a few weeks ago for an okay price all things considered. It’s no show piece by any means and it had the original output transformer replaced at some point, so I don’t feel too bad about saying this: I want to Dumble it. It sounds okay as it is, but it has that muddy mids thing Fender amps that’ve been played hard always seem to develop. I’m budgeting for a once-over and I figured that if it’s going to be cleaned up and brought back into fighting shape, I might as well have the mods I want done to it.

As for what I want: I have no clue what to ask the tech to do. There’s quite a few well-documented Ultraphonix mods on the forum already. While those are great launching points, they aren't necessarily what I'm after. They all seem to be based on the Bluesmaster preamp, which has been described to me as warmer and more mid-rangey. Not that I don't like that, I just want something more along the lines of whatever the idea of the "Dumble Clean" is: full-sounding, but crystalline through most of the volume pot sweep. This Bandmaster is going to be paired with either a 100-watt Twin modded back to the AB763 (which I have no plans to mod further) or a Two Rock Tradition Clean I’ve been saving for. As you might be able to tell from my amp choice, I’m kind of a clean freak and I’ve been obsessed with getting that huge 2006-2010 John Mayer clean without spending too much money… which is kinda hard to say with a Two Rock on the way. I want all my amps to be in that 'clean only' mold, but sound different enough from each other to justify having them.

So my question is: what’re my best options for getting that hi-fi clean out of my Bandmaster? Is this even something possible out of the 40-50ish watt Fender platform? I have some ideas (changing the input resistor, Skyliner EQ, bigger OT, bringing up the voltage in the preamp up, something with the phase inverter), but my knowledge about how amp circuits actually function is somewhere between diddly and squat. What I do know is that there are some later (90's) ODSes are said to be super clean on channel 1 and that a handful of Steel String Singers I really like (002, 004, 005) were built with the Classic preamp. Something I know for sure: my amp is getting a Pacific Transformers Bassman OT and I'm most likely replacing the speakers in the cab with EVM12Ses. Do with that what you will.

Any pointers will be very much appreciated. Audio clips, too; I can always use those. I want to compile as much info I can so I won't make the life of the guy I'm taking the amp to a living hell.

Also: long time listener, first time caller here. Please be nice. I have a gut feeling there’s been 100 posts like this.

[Guy77]

Congrats on the beautiful amp and cab!

I just wanted to chime in regarding your cab. Do you have the JBL speakers in there from that era?
If you do I would hold on to them. I played a cab like yours with the JBLs and it sounded incredible with a JM/Wonderland amp and another SSS amp I built.

Cheers
Guy

[overlandltd]

Congrats on the beautiful amp and cab!

I just wanted to chime in regarding your cab. Do you have the JBL speakers in there from that era?
If you do I would hold on to them. I played a cab like yours with the JBLs and it sounded incredible with a JM/Wonderland amp and another SSS amp I built.

Cheers
Guy

The cab right now has some oddballs; Marshall McKenzie speakers. They're aluminum capped, but that's about all they have in common with the D120F. Very tired sounding, too. Like I said, this amp was played hard and these speakers have been in that cab since the 70's. The tech I'm taking it to orders a lot of speakers from Weber for builds under his own brand (I think he's technically a dealer). He's worked with them to make a hybrid ceramic/Alnico speaker that's sounds almost spot-on with an original I tried it in a modded Princeton and it had that chattery high end of a '66 Twin with original JBLs I've played, so I'm sold on them. I'll definitely ask about them when I take the amp in, but if he can't get more, I'll poke around for reconed K120s or those Missing Link Audio Black Widow hybrids.

I've always wondered about JBLs with Dumble-style amps. I've always associated them more with either G12-65s or EVMs, but I know of a few odd examples like the Steel String Singers made for Henry Kaiser. Maybe I should look into the preamp of SSS 004 as a start then? Since that had D131s in its original cab.

[Guy77]

Congrats on the beautiful amp and cab!

I just wanted to chime in regarding your cab. Do you have the JBL speakers in there from that era?
If you do I would hold on to them. I played a cab like yours with the JBLs and it sounded incredible with a JM/Wonderland amp and another SSS amp I built.

Cheers
Guy

The cab right now has some oddballs; Marshall McKenzie speakers. They're aluminum capped, but that's about all they have in common with the D120F. Very tired sounding, too. Like I said, this amp was played hard and these speakers have been in that cab since the 70's. The tech I'm taking it to orders a lot of speakers from Weber for builds under his own brand (I think he's technically a dealer). He's worked with them to make a hybrid ceramic/Alnico speaker that's sounds almost spot-on with an original I tried it in a modded Princeton and it had that chattery high end of a '66 Twin with original JBLs I've played, so I'm sold on them. I'll definitely ask about them when I take the amp in, but if he can't get more, I'll poke around for reconed K120s or those Missing Link Audio Black Widow hybrids.

I've always wondered about JBLs with Dumble-style amps. I've always associated them more with either G12-65s or EVMs, but I know of a few odd examples like the Steel String Singers made for Henry Kaiser. Maybe I should look into the preamp of SSS 004 as a start then? Since that had D131s in its original cab.

Scoring a K120 would sound great with almost anything. Believe it or not I got great tone for Dumble style builds from this 15in speaker: Eminence Legend 1518 , it has a silky smooth sound, way better sounding than the 12in version.

A great way to go without totally changing the complete inside of the amp is to start with a classic tone stack from the 124 that Robben Ford had before changing it to high plate Skyline. I think you will bond well with that preamp and then later if you wanted too you can switch that to Robben's more aggressive High Plate Skyline Preamp. This way you don't completely gut your amp.

Here is the link to the 124 Classic Low Plate
https://ampgarage.com/forum/viewtopic.php?t=12872

Cheers

Guy

[fred.violleau]

Hey Overlandltd,

Having built a few dumble clones (HRM, #102, #40, #Bluesmaster clean channel, ultraphonix High gain, and a John Mayer Sig clone), they all have different tone stacks;
The skyliner tone stack is very typical Dumble glassy tone (#102), but more aggressive (glassy)
John Mayer sig and #40 closer to Fender round and wooly
Ultraphonix is closer to a marshall tonestack, so different than what you are looking for.
I would go either with what Guy suggested or John Mayer Sig or #40 which are all close;

Good luck with the mods !


Fred.

[overlandltd]

Thanks for all the pointers so far. I’m starting to compile a list to give the tech, as well as some references to send along to him. Here’s what I have, pending some potential additions:

General Bandmaster fixes + mods
Once-over on filter caps: turned up, it’s really noisy, which was the same problem I had with my Twin before it was serviced. I’m starting to think they’re on their way out.
Replace microphonic V2 (+ V1, potentially?): You can definitely hear tapping on V2. V1 is a little noisy, but I can't say if it's that tube or V2 is that sensitive. Either way, I’m thinking Tung-Sol new productions?
Fix tremolo (ticking, lack of depth/speed)
Cesar Diaz tremolo disconnect: I know I said I wanted a clean-only amp, but having that extra horsepower on tap will never hurt, right?
Pacific Transformers Bassman OT
Replace speakers in cab w/ 1 EVM12S + 1 JBL D/K120: I’ve heard good things about mixing a 12L with JBLs, so maybe I’ll try that with the 90’s 12S I already own. This cab is gonna be ungodly heavy, but being able to use it with basically anything I can throw at it is worth the back pain. I believe the PRS cabs John Mayer has been using are the same size as the 60’s Bassman/Bandmaster cabs and I’ve read he’s using EVM12Ls in them. That’s definitely the vibe I want, but a little crisper.

Dumble Mod Ideas
Classic Low Plate front end: I can’t read schematics for the life of me, but I hope it’s not too different from the AB763. Well, not different enough to require a complete rebuild of the amp. I definitely need to do my research.
Stiffen power section: It might just be that the caps are starting to drift in value, but the amp right now is a little too spongy and loose for my liking. Maybe that’s the Fender 40 watt thing, but I’m too used to that Twin experience. If I have it modified to be basically half of a Twin, maybe I’d like how it feels?
Black chicken head knobs + blue jewel: going for that Two Rock vibe with the black panel.