Hybrid D-style tone stack to Fender style tone stack switching

[tubenit]

Guys, I posted this on the Amp Garage also to see what the Dumblish cloners think about the idea. Since some of you are familiar with Dumble clones and have built one, I thought I'd post the idea here also to see what you think?

---------------

I will own up front that I've never built a true Dumble clone. I've stolen/borrowed lots of Dumblish ideas building the Tweed BluesMeister, Carolina Overdrive Special and Tweed Overdrive Special (EL34 World schematics). (Those are all cathode biased amps) Not being a purist, I spend a lot of time pondering new ideas in these amp designs.

 So one of the things I've noticed over the years of reading TAG and the Dumble forum, is the comment that "it's a compromise" in these amps with either having the clean being fabulous tone or the overdrive being fabulous tone. And at times, posters have mentioned the Fender clean tone as being a tone value that they hold as a reasonable standard for clean tone. And that getting both the clean tone great and the overdrive great is somewhat of a challenge at times.

 So, I was thinking maybe there is a way to have the clean tone be more Fenderish & then switch to the overdrive tone be more Dumblish?

 That led me to look at the tone stack and consider a hybrid approach with relay switching. So, if the midboost is R1 (relay 1) and the hybrid switch is R2 and we labeled the clean to overdrive switch as R3 ……………………

Then one possibly could have R2 and R3 switch simultaneously. :?

 I acknowledge that the slope resistor would be different (68k Fender vs. 100k Dumble). (Although, I think D-102 has a 68k slope resistor). And the bass pot on Fender is 250kl vs. Dumble 500ka. And the treble cap on Fender is 250p vs. Dumble 326p (when midboost is off).

 So, there are differences & perhaps those would negate trying a hybrid approach? Having said that, I am thinking this hybrid idea could get the clean tone closer to a Fender clean tone? And maybe close enough to have the idea be worthwhile?

 So, the idea would be the Fender inspired side of the hybrid tone stack in the clean mode. And then when R2 and R3 are switched simultaneously, then the overdrive would be using the typical Dumblish values? OR ………….. someone might prefer not having them switch simultaneously to have even more tone options?

 One question I have is if the 4.7M resistor to ground in the mid pot area is needed? I simply copied what was done in the treble topology of the D-style tonestack for switching.

Thoughts?? (I attached an ExpressSCH schematic, if someone would like to edit the idea and revise it).

With respect, Tubenit

[jjasilli]

My solution would be to build a true 2-channel amp (or even 3-channel), with relay channel switching.  Rivera I think started modding 2-channel Fender amps like this in the 60's or 70's.  E.g.: Ch 1 converted to Marshal; Ch 2 remains Fender with reverb & trem.  Could just as well be Dumble & Fender.  This would preserve the complete preamp topology of each type of amp.  There may be some compromise with PI and power tube circuits.

[sluckey]

My solution would be to build a true 2-channel amp

+1

[tubenit]

My solution would be to build a true 2-channel amp (or even 3-channel), with relay channel switching.  Rivera I think started modding 2-channel Fender amps like this in the 60's or 70's.  E.g.: Ch 1 converted to Marshal; Ch 2 remains Fender with reverb & trem.  Could just as well be Dumble & Fender.  This would preserve the complete preamp topology of each type of amp.  There may be some compromise with PI and power tube circuits.

Make that another +1 with my vote also.  That's what Geezer did with this amp:   https://soundcloud.com/dageezer/twin-ultraphonix-test-1

Having said that,  this idea is intended as a mod for an already built amp.  I currently have made a mod to my Carolina Overdrive Special (*see attached) that is useful to me.  I'm probably gonna try this idea in the original post now and see what I think.

With respect, Tubenit

*EDIT:   Having spent some more time today playing this in it's current configuration (see attached schematic on this post), I decided to leave it
             this way because I also like the OD tone with the caps in series as well as the .01 bypassed.

[Backwoods Joe]

Tubenit, did Geezer ever finalize the "twin ultraphonix"? And if he did, did he turn loose of the schematic? What I'm hearing sounds.....as the locals say round here, "it has a good sound to it"

[tubenit]

My understanding is the amp design was finalized.  The schematic was not shared openly.  Think sort of a Fender AB763 preamp into LTPI & one of the entire Dumble preamp and OD into the same LTPI using A/B switching. And then his tweaks/mods that were added. I gave him a d-later but don't remember if it was used in the recording?


With respect, Tubenit

[Backwoods Joe]

K Thanks. It really sounds awesome, but i'm sure his tweaks are bringing THAT TONE!