79 Dumble Overdrive Deluxe

[capgreed]

I made a REALLY rough first attempt from what I see , but must be fucking up some things here ....Looks weird ! Probably some shenanigans under the board

[aab0mb]

Gut shots from one the clones should help decode this thing. Finally!

[aab0mb]

More pics. Sorry I don’t have pics under the dog house.

[Aaron]

Great photos! Thanks for these. Will draw a schematic later tonight when I finish work.

Thanks,
Aaron

[capgreed]

Ouuuuuu. ! Noice ! =D

Much more exploitable than the amplified nation gut shot !

Thanks a lot man !


NB: by the way I corrected a few gross errors that sled into my first schematic of the preamp

[capgreed]

By the way , what is that seemingly 18-78ohms ( can't figure out the color of the first ring brown ? purple ? ) resistor grounding the entry of the tone stack ( I haven't put it in the scheme yet ) ?
What's the point of such a tiny resistor there ?

Have I got it somehow wrong on the channels config ( I still got big doubts on the clean/V3 part ) ? There's no switching and only two plugs ...Should be something like that no ( despite the fact that , yes on most dumble's designs on the clean there's only ONE gain stage before the tone stack )?

By the way is it 2k7 or 27k in parallel with the 25uf on V3 ? I put 2k7 because it seemed more logic , and I'm waiting for debate pointers on that ...

Apparently on the clones ( not the amplified nation version ) the V1a grid stopper is 68k , I'm gonna have to correct that on a Version 3.0 .....

[aab0mb]

By the way , what is that seemingly 18-78ohms ( can't figure out the color of the first ring brown ? purple ? ) resistor grounding the entry of the tone stack ( I haven't put it in the scheme yet ) ?
What's the point of such a tiny resistor there ?

Have I got it somehow wrong on the channels config ( I still got big doubts on the clean/V3 part ) ? There's no switching and only two plugs ...Should be something like that no ( despite the fact that , yes on most dumble's designs on the clean there's only ONE gain stage before the tone stack )?

By the way is it 2k7 or 27k in parallel with the 25uf on V3 ? I put 2k7 because it seemed more logic , and I'm waiting for debate pointers on that ...

Apparently on the clones ( not the amplified nation version ) the V1a grid stopper is 68k , I'm gonna have to correct that on a Version 3.0 .....

The preamp looks sort of like a cascaded Plexi aka the Plexi “one wire mod”. Google that and you’ll see it. There isn’t a dedicated clean channel setup.

Input > v1a > pot > input 2 (deactivates v1a) > v1b > pot > v2a > v2b is the cathode follower > tone stack

I think that resistor you’re questioning on the input of the tone stack is the cathode follower resistor on the cathode. You might be mistaken about the value but follow it to the v2b cathode, yeah?

The second or “low gain” input defeats the first triode stage just like a jcm800 does it.

[capgreed]

By the way , what is that seemingly 18-78ohms ( can't figure out the color of the first ring brown ? purple ? ) resistor grounding the entry of the tone stack ( I haven't put it in the scheme yet ) ?
What's the point of such a tiny resistor there ?

Have I got it somehow wrong on the channels config ( I still got big doubts on the clean/V3 part ) ? There's no switching and only two plugs ...Should be something like that no ( despite the fact that , yes on most dumble's designs on the clean there's only ONE gain stage before the tone stack )?

By the way is it 2k7 or 27k in parallel with the 25uf on V3 ? I put 2k7 because it seemed more logic , and I'm waiting for debate pointers on that ...

Apparently on the clones ( not the amplified nation version ) the V1a grid stopper is 68k , I'm gonna have to correct that on a Version 3.0 .....

The preamp looks sort of like a cascaded Plexi aka the Plexi “one wire mod”. Google that and you’ll see it. There isn’t a dedicated clean channel setup.

Input > v1a > pot > input 2 (deactivates v1a) > v1b > pot > v2a > v2b is the cathode follower > tone stack

I think that resistor you’re questioning on the input of the tone stack is the cathode follower resistor on the cathode. You might be mistaken about the value but follow it to the v2b cathode, yeah?

The second or “low gain” input defeats the first triode stage just like a jcm800 does it.

Thanks for your answer ....
Well it sure as F didn't sounded like a jcm800 in the vids ....But I'll try that config and see if it sticks better to the layout ^^ I sure as hell wouldn't have guessed the "low gain" ( in the "clean" soundbites ) was going through like 3 gain stages ^^ the guy must have had his guitar volume pot on like zero ^^
By the way , which "pot" si wired just after v1a to you on the panel of the overdrive deluxe ? "overdrive " ? Volume's already in the tone stack so ...yeah ...What else ? "Level" ?

[capgreed]

Sorry I got back to making the schematic so late , but I had massive amounts of stuff to take care of those last two weeks ^^

*Erased link*

You'll tell me if you see things that require to be improved ....

[JD0x0]

By the way , what is that seemingly 18-78ohms ( can't figure out the color of the first ring brown ? purple ? ) resistor grounding the entry of the tone stack ( I haven't put it in the scheme yet ) ?
What's the point of such a tiny resistor there ?

Have I got it somehow wrong on the channels config ( I still got big doubts on the clean/V3 part ) ? There's no switching and only two plugs ...Should be something like that no ( despite the fact that , yes on most dumble's designs on the clean there's only ONE gain stage before the tone stack )?

By the way is it 2k7 or 27k in parallel with the 25uf on V3 ? I put 2k7 because it seemed more logic , and I'm waiting for debate pointers on that ...

Apparently on the clones ( not the amplified nation version ) the V1a grid stopper is 68k , I'm gonna have to correct that on a Version 3.0 .....

The preamp looks sort of like a cascaded Plexi aka the Plexi “one wire mod”. Google that and you’ll see it. There isn’t a dedicated clean channel setup.

Input > v1a > pot > input 2 (deactivates v1a) > v1b > pot > v2a > v2b is the cathode follower > tone stack

I think that resistor you’re questioning on the input of the tone stack is the cathode follower resistor on the cathode. You might be mistaken about the value but follow it to the v2b cathode, yeah?

The second or “low gain” input defeats the first triode stage just like a jcm800 does it.

Thanks for your answer ....
Well it sure as F didn't sounded like a jcm800 in the vids ....

I think they were just speaking to 'inserting' the guitar input at the second triode ala an 800. Probably doesn't have a cold clipper stage there, which is why it sounds different. I think Marshall's implementation was a bit silly, because of the gain control in front of the triode, and it being a cold clipper stage makes the clean "Channel" on JCM800's very weak and anemic. Probably works a lot better on a 'one wire mod' type setup, where the stage is biased a bit warmer and has a cathode bypass cap, for more gain.

[capgreed]

By the way I put 10k at the grid stopper position in front of V1b , but it's totally up for debate ....The first ring on the resistor is masked off by the heat shrink tube , so I just asked myself what was commercially available most generally as far as values with black as a second ring and orange as a third , in most cases it's a 10k , I thought it was a little low , but then again it's the "clean" channel ....So don't hesitate to repost the schemo with annotations and improvements ...In the same vein I put a 4.7M value up in the air near the bright switch because it's on the gut shot but I have no idea how they wired the damn thing and why it's there ....There are versions of the rock/jazz switch I saw with a 1M grounding the whole conundrum , but 4.7M ??? There's a 4M7 resistor yes on some Dumble designs but on a mid boost switch ( it's actually on the ceriatone OTS mini 20w lunchbox layout ) not on a Rock/Jazz ! The values of the blue tantalums caps are a total crapshoot , and actually there are TWO 220k resistor blue cap in parallel in the gut shot , I put just one in the schematic because I don't like to add up elements that I don't see the functional use of yet ....I won't be the one able to solve those little pebbles on the way , most likely it's gonna be someone in here with MUCH more experience with the gazillion designs ideas Howard Dumble crafted along the years ...

[aab0mb]

More pics and better/updated schematics over here in the discussion area.

https://ampgarage.com/forum/viewtopic.p ... 3&start=15


As a matter of courtesy and Dumble Files Section hygiene, I suggest we use the linked thread for all speculation and testing until we’re ready to post a semi permanent Schematic and layout here in the Files section. Seems appropriate.

Respect,

-A-

[capgreed]

More pics and better/updated schematics over here in the discussion area.

https://ampgarage.com/forum/viewtopic.p ... 3&start=15


As a matter of courtesy and Dumble Files Section hygiene, I suggest we use the linked thread for all speculation and testing until we’re ready to post a semi permanent Schematic and layout here in the Files section. Seems appropriate.

Respect,

-A-

No problemo ...i'll erase my links !