Dumble Bandmaster Gator UltraPhonix Build

[Charlie Wilson]

Ok so I have no inside information on this particular amplifier other than the picture. It looks to me like the cap across the tremolo roach and the PI out are the same sized cap. Typically the cap across the tremolo is a .01 or .02. Also, a 200v cap to ground is too low a voltage rating for the 400 or so volts sitting on top of it in the tremolo position. You said that you have your bass control on zero, that to me is an unusable bass control. For these reasons I think that cap is a smaller value than .1 and most likely .02. Finally, that cap across the 100k is definitely not .02. I am guessing .002-.005. It would probably take 5 min to swap these out and listen.
CW

[rccolgan]

Ok so I have no inside information on this particular amplifier other than the picture. It looks to me like the cap across the tremolo roach and the PI out are the same sized cap. Typically the cap across the tremolo is a .01 or .02. Also, a 200v cap to ground is too low a voltage rating for the 400 or so volts sitting on top of it in the tremolo position. You said that you have your bass control on zero, that to me is an unusable bass control. For these reasons I think that cap is a smaller value than .1 and most likely .02. Finally, that cap across the 100k is definitely not .02. I am guessing .002-.005. It would probably take 5 min to swap these out and listen.
CW

Hey Charlie! Good stuff here. I rifled through my old photos and came across a Welagen with 102k cap across the 100k and 47nf across the roach. I would guess that the blue cap is 47nf and the AC coupler in the PI is 47nf as well since I've seen a Plexi or Marshall with .047 before. I'll update my schematic later today and swap out a few components

I did find a Marshall 2203 with a .022uf AC Shunt capacitor but also interesting is that Marshall GNFB is attached to the 8ohm tap and the original Bassman tap is only 4ohm! So I guess it could go back to that blue cap is 22nf It's also interesting that the reissue changed the AC shunt capacitor to 100nf. So it's really all over the place.

I do have my GNFB attached to the 4ohm tap so it could account for the bigger bottom end. I'll move to the 8ohm tap on my OT and maybe that'll make things tighter. (Thanks, Rafael, for the calculations on this!)

[Charlie Wilson]

Cool, but did you try and listen to a value other than .1?
CW

[Charlie Wilson]

I have some of those square blue metalized polyester caps and I compared the sizes and yeah .047 seems about the right size. There are many different makes of caps that look like that, mine are Xicon, but the sizing seems about the same.
CW

[rccolgan]

I have some of those square blue metalized polyester caps and I compared the sizes and yeah .047 seems about the right size. There are many different makes of caps that look like that, mine are Xicon, but the sizing seems about the same.
CW

Cool! Thanks for investigating!

I swapped out the AC Shunt (this is what Rob Robinette calls it, so that's where I got that name from) to .022uF and the tone is much more present! I am not too familiar with how the presence circuit works, yet, but this does seem to tilt the tone into a brighter top end. So I guess it's possible again that the blue xicon cap is 22nf or could be 47nf at this point. I am also happy to say that my bass controls are much more "normal" now after moving the GNFB to the 8 ohm tap as well as changing that AC shunt cap to 22nf.

Now it seems like I have to play around with speakers as the one I'm using with G12-65H don't pair well with this amp. With my strat, the quacky 2/4 position almost disappears and isn't responsive at all with this amp & speaker cabinet. I then tried with my SSS #004 cabinet with JBLs and the tone was much better paired. It's definitely different compared to the mid scoop of a BF Fender. I'll try soon with humbuckers and see. Maybe I'll have to deeply mod one of the channels back to a BF fender or something. The tone now is kinda wooly, if that makes sense.. It's good! Different from what I'm used to. Probably would pair well with another amp but I'll keep tweaking.

[Charlie Wilson]

Trying flipping the orientation of your mid caps.
CW

[Marshmallow]

Hi All, (long time lurker, I just look and build)

Just built the amp but a single channel using Ryan's schematic, with Reverb and Princeton tremolo. Got plenty of od/break up on tap. It's 6l6 rectified. Reverb is using a 6bm8 tube to free up a tube.

[Guy77]

Congrats! Great work.

Cheers
Guy

[Marshmallow]

Congrats! Great work.

Cheers
Guy

Thanks Guy!

[jabguit]

It's 6l6 rectified.

Come again??

cheers,

[rccolgan]

Hi All, (long time lurker, I just look and build)

Just built the amp but a single channel using Ryan's schematic, with Reverb and Princeton tremolo. Got plenty of od/break up on tap. It's 6l6 rectified. Reverb is using a 6bm8 tube to free up a tube.

Awesome work!! After you & I talked, I ordered A25K pots for my mids. I cannot wait!

I ended up revisiting the PI tube type after I adjusted the AC Shunt capacitor to 22nF. The 12AX7 was really poking out my pick strike and strums. Almost too much. I swapped to 12AT7 and now the amp is pretty perfect! Silky smooth. I'm lending it to my friend who's a great player to do a review and clips for everyone. It's a little soon to tell but this might be my go-to amp!

[rccolgan]

Video review of my UltraPhonix build by Tone Wise Productions. He's more of a rocker type of player so he found those tones pretty easily with his PRS guitar. I play it with my Silver Sky (strat) and it does clean tones nicely with the volume around 5. It is darker so we both had the treble up quite a bit but it's not too weird. It rounds out bright pedals and such this way which is nice.

[GAStan]

Sounds great Ryan, I LIKE it!

[rccolgan]

Thanks!! Rafael and I keep going back and forth how much the amp sounds a whole like Kenny Wayne Shepherd's "My Guitar is Crying"

To me, it fits really well in the blues rock genre. Quite a bit different from what I'm used to with SRV/Mayer but I'm really digging it the more I listen to The Black Keys, Dirty Honey, Marcus King, etc and I hear that similar low-gain hollow blues tone through humbuckers.

[Charlie Wilson]

Ryan, I confirmed(don’t ask me how) that the cap across the tremolo roach is .047 and across the 100k is .001. Which would also make the PI cap .047. Your amp sounds great.
CW