Hybrid D to F tone stack idea

[10thTx]

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 to 150k Dumble). 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, 10thtx

[10thTx]

As an FYI, this is currently what I have in my Carolina Overdrive Special. I find it to be a useful mod & I enjoy having access to contrast in mid tones. It's quiet when it switches just like the midboost is. I like the OD tone both with the .04 and the .01 in series as well as the .01 bypassed with just the .04 mid cap to the 250k pot.

With respect, 10thtx

[xtian]

Actually, I hear the D clean as distinct from F, and awesome in its own way. I love my D builds BECAUSE of the awesome D cleans!

Carry on.

[Charlie Wilson]

Not sure where you are getting a 68k slope resistor from.
CW

[10thTx]

Not sure where you are getting a 68k slope resistor from.

IF you're referring to my erroneous comment about D-102 having a 68k slope resistor, it was an error in a drawing I did some years ago. Correct value would be 150k as I understand it. I deleted the comment in my first post to avoid further confusion.

with respect, 10thtx

[FUCHSAUDIO]

Having been down this road before, the best sonic solution is two tone stacks you can switch. You could then chose either stack for clean or dirt. I breadboarded this few years back. Both stacks can then be the “best” of each kind, or tweaked within themselves, and then chosen for the sound you want. Lots less relays, switching, tweaking, etc.

[10thTx]

Andy,

Thanks for offering your thoughtful insights and experience regarding this idea! I appreciate your knowledge and contribution to the forum.

with respect, 10thtx

[FUCHSAUDIO]

Thanks . I think the values and tapers of pots, and all the switching required just make this somewhat impractical. My two cents fwiw.

[10thTx]

As an FYI, I am very happy with how I've implemented this in my Carolina Overdrive Special (schematic earlier in thread). And it only uses one relay for switching.

I use this more then the mid-boost switch. I find it gives me two very useful tones in clean and two more very useful tones in the OD. And it's dead silent in the switching.

And with one extra cap, one resistor, couple pieces of small wire and one relay ………. fairly low component count for this mod. Someone could simply use a spdt toggle switch if they wanted and not have it relay switched?

However, the COS is different then a Dumble clone & perhaps it would not be that useful of a tone switching idea in a D-style amp?

With respect, 10thtx