Dumble Bandmaster Gator UltraPhonix Build

[rccolgan]

I figured I should kick off a thread now that I'm about 1/2 way done building an UltraPhonix to externally resemble the Gator tolex grill UltraPhonix that was unearthed by Emerald City Guitars and sold to John Mayer for Dead & Company residency at the Sphere. Living Google Photos Album link with everything in full resolution: https://photos.app.goo.gl/J1rozbLLKT71Sf5C6 I found the UltraPhonix emblem via https://www.droplightind.com/products/badges and had them scale it down to 6" long and I found some proper alligator black marine grade tolex that looks exactly like Dumble's original.

Started off life as a Craigslist find Bandmaster chassis and some components. Was missing a OT, headshell, and the PT heater center tap wires looked cooked. This is fine because I wanted to upgrade the OT to a Bassman per UltraPhonix style and I needed a new head shell... Perfect! (and the price was right!) As for the circuit, I'm using the reversed engineered circuit of this Bandmaster. https://ampgarage.com/forum/viewtopic.php?f=4&t=30285 . I'm not into overdrive or gainy Dumble tones, so the clean platform is very intriguing to me.

Next was stripping everything and reconditioning the chassis.. Funny enough - Barkeeper's Friend was absolutely amazing for taking the rust off and any of the impurities.. unfortunately that also means the rubber stamped date code but I'll add it back with a sharpie. This project is not for the faint of heart!

The goal of the circuitry bits is to make this amp not exact 1:1 component-wise, but to build it for longevity and durability. I designed the PCB myself so I could leverage the FR4 low moisture-absorption properties. I've been watching Lyle's videos on YouTube (Psionic Audio) and I never, ever want to go through this amp in the future and have conductive boards, drifting carbon comps, conductive cloth wiring, etc. That said, I'm using Tokyo Cosmos (TOCOS) epoxy sealed pots almost everywhere except for the tremolo speed and intensity. I opted for Weber tremolo disconnect pot for removing the 50kra pot loading the circuit for some additional oomph. 10k mid pots added where the second input is located.

As for resistor selection, I'm using Xicon 1W resistors in place of Carbon Comps and TE 1/2W H4P metal film where the metal film locations are. I have some 2W 2.7k cathode resistors around that I'm using and a 2W 100k that I think are Ohmite. My logic here is that this particular Bandmaster I'm trying to copy MUST be one of the last that Dumble ever built. So, in this era, that TweedleDee that he built for the Fender executives ~2017 seemed to have Xicon resistors in them. I also tracked down the knobs that Dumble acquired and they were for sale a few years ago so I'd lump this in the late-modern era build. I found similar looking ones and the exact size from Alco.

Capacitors are largely 6PS. I'll come up with a BOM when I'm done. Wire is Weico 22ga tinned stranded wire with the same color coding as the original Fender. Belton sockets.

As for power supply, F&T caps with stock dropping resistors. The 4.7k resistor I'm chose to use a 2W carbon film sorta like what Dumble does for his ODS. The main reservoir caps, I'm going with 2x 220uF like the ODS as well. I don't think we've confirmed anything on the thread what the supply looks like on the Bandmasters so I'm taking an educated guess.

I think that's it off the top of my head.... data dump while I'm waiting for my next day job meeting to start...

Update 9/20/24: Adding my final schematic

TTG_UltraPhonix_bandmaster_ab763_schem.png

[martin manning]

Very slick! Love the fiberboard replacement.

[ThePanda]

Looks great!
I am excited to hear it!

Did you go Hammond or Heyboer for the transformers?

[rccolgan]

Very slick! Love the fiberboard replacement.

Thanks, Martin! It means a lot coming from you The silkscreen font is "Engineer Hand" which is very close to the official Fender schematic handwriting.

Looks great!
I am excited to hear it!

Did you go Hammond or Heyboer for the transformers?

The amp Gods were on my side and while I was thinking of starting this project, I got an alert from eBay that a NOS ClassicTone Bassman OT transformer was available so it was meant to be. PT and choke are Hammond. I've had good luck with them in the past and CE Dist had a great sale last month on them. I'm not much into PT mojo

[rccolgan]

The amp is alive! A few things I missed or made a mistake but it was small things and easy to rectify.

Last thing I'm chasing down is the tremolo. There is a static at the very top of the pulse. I can quiet if down with lead dress quite a bit but comes back when I strum the strings. The schematic and layout I followed is in the first post. Has anyone who built this amp and/or trem have insight? I know the tick cap across the roach is already installed (22nf in my case, per dumble).

Here is a video of and sound clip.
https://youtu.be/qW9q9s9s6cw?si=e8C3Icq9oLRbBIhC

Note: I was trying to see the difference between 100k and 50k cathode resistors so that's why it's hanging up there. Also note on the layout comparison pic below I was missing the 220k on mine but I added it in after I made the pic

[Abe5150]

Nice Ryan looks good! No insight on the trem I'm still trying to fix mine on a 6g3 build.

[rccolgan]

Nice Ryan looks good! No insight on the trem I'm still trying to fix mine on a 6g3 build.

Thanks! Is it modded to be like this Bandmaster too? The trem definitely sounds great with the mods. Real deep and throaty! I tried another tube but same static/zap on the top again.. ugh. I honestly don't think I'll use the trem at all afterwards but it's easiest to tackle now and to feel "complete" about the build lol

[Abe5150]

No its not modded, just a straight 6g3 build, but I did use Pacific Transformers.

[rccolgan]

No its not modded, just a straight 6g3 build, but I did use Pacific Transformers.

Ah! Got it.. hopefully you'll get it fixed one day!


As for my troubleshooting, today I tried the suggestions here (thanks, Chris!)
https://www.effectrode.com/knowledge-ba ... h-tremolo/

I tried bundling wires and brought the trem cathode ground and the 100k speed resistor to the same ground point and nothing. The weird part is that the trem starts of quiet, and the tick comes in after a few pulses. The harder I strum, the amplitude of the tick increases as well... I feel like this is a capacitance or something.

I looked at a Welagen Deluxe Reverb too and that had a 50uf/50v cap on the cathode so I clipped in another 25uf cap but that didn't solve the issue either. Hmm..I might need to get more intrusive tomorrow unless someone here chimes in haha

[Charlie Wilson]

Try pushing your PI entrance grid wire away from the tremolo cathode wire.
CW

[rccolgan]

Try pushing your PI entrance grid wire away from the tremolo cathode wire.
CW

Thanks, Charlie! I tried this with no luck .

I also didn't know that TOCOS pots do not connect the back housing to the front where it would naturally be grounded. I have a buss wire for all of the preamp so ground loops should be minimal. I thought for sure running a separate buss ground for the back of the TOCOS pots would solve it but it just further lowered the noise floor

I did get some success this morning tho. I drastically minimized the idle tick by bundling together v3 1-2-3 as well as wrapping the trem footswitch wire around the plate wire. Floating them a bit away from the chassis. It seems like most of the idle tick can be reduced by pinching with my fingers around that plate wire so I thought wrapping it with the grounded footswitch wire would act as a pseudo shield. It did seem to help! Everything goes out the window once I strum the guitar strings and then the crosstalk comes back in at the top of the pulse.

I moved around the control wiring as well with no change.. I'm going to work on the head shell and give it some thoughts..

[Ariel Meyer]

curious to hear this as i've just got a vintage bandmaster for repair, it sounds great, I guess those mods will make it a bit more drivey ? with an almost marshall PI and mixer resistors, bigger cathode caps... interesting

[rccolgan]

curious to hear this as i've just got a vintage bandmaster for repair, it sounds great, I guess those mods will make it a bit more drivey ? with an almost marshall PI and mixer resistors, bigger cathode caps... interesting

Right now I have a 12at7 in the PI and it's a clean machine. Lovely, actually. The Nor channel sounds clearer & more hifi compared to the Vib channel even though the stack is pretty close! I'll try with pedals in the coming days and see if that changes my opinion but I'm really enjoying the amp so far.. it's really balanced! I have the bassman OT also so I think that adds a touch of headroom.

Reminds me of my Vibroking before it starts breaking up

[m.alexander]

Ultra Phoenix-2.gif

i use this schematic

[Ariel Meyer]

An interesting exp would be to mos the 2nd chan to a Suhr bella, whixh is also a dumble modded bandmaster inspired amp

V1a
180k Rp
Rk 2k7 bypasaesd with Ck 22uF

Tone stack the aame, just 1MA bass pot with 10k mid pot
Treble has 220k going into a master pot, probably 500kA or 1Ma

V1b
Rp 120k
RK 1.8K with 22uf going into a switch for booat on or Off

Just for a different clean pedal platform or even semi sriven clean