Fender Rework to Dumble

[GoghVan]

Hello All,

I'm new to the Amp Garage and new to the Dumble circuits.

I'm interested in getting input on a schematic to use as a guide to Dumble a Fender. I have a Bandmaster/Twin (Bandmaster X'Formers in a Twin chassis) in a Twin Head Cab and a SF Princeton in a Allen PR cab.

I'd prefer not to have a lot of boards and relays etc. I like a clean, open, transparent sound on the clean ch, and a smooth driving tone in the OD. I realize that may not be possible in a minimalist package but I'm open to suggestions. I'm also trying to keep the weight and size down.

Any opinions on a good schematic as a start? I am experienced in electronics...good equip...load, scope, freq. counter, etc....and have rebuilt a 1/2 dozen amps.

Regards

[M Fowler]

Here is Brownote Dlite schematic and Normster layout in a 16x8x2 chassis.

[David Root]

I've done one in a BF Princeton Reverb chassis.

If you use multiple node can caps you can conceivably lose the PS caps board.

No FET input, lose another board.

That leaves you with the same main board and PS/Bias supply board as the Fender, but you have to have one relay, so add back in one small board.

If you are thinking of doing this point to point with no boards at all, forget it, you'll get so many parasitic oscillations you won't believe it!

[Bob-I]

Normster did a Bassman to Dumble conversion quite awhile ago but the layout is still posted.

http://ampgarage.com/forum/viewtopic.ph ... ht=bassman

[GoghVan]

Thanks for the input guys. I've worked on probably a 1/2 dozen Fender amps where I rebuilt the amp from the ground up using Sprague Atoms, F+T, 715 orange drops, Koa, and PRP resistors, new x'formers etc. but always felt there was something lacking in the OD department (clean tones...I get) . Pedals, usually, don't cut it for me as they almost always sound too harsh OD'g the input circuit and have hesitated experimenting with relays to switch a tube drive circuit.

Of course I'd heard about the Dumble amps.....but never played or listened to one until recently via an internet comparison over my Bose spks. As a minimalist I'll need to compromise on the relay and extra gain stages to get a better OD "Tone".

There's a lot of great info hear. Thanks for the input.

[Bob-I]

Thanks for the input guys. I've worked on probably a 1/2 dozen Fender amps where I rebuilt the amp from the ground up using Sprague Atoms, F+T, 715 orange drops, Koa, and PRP resistors, new x'formers etc. but always felt there was something lacking in the OD department (clean tones...I get) .

Component selection is important in these amps. The most critical are plate load resistor, they must be high quality metal film (yea I know, that's against everything you about amps) and all other resistors are carbon film typically, although Dumble tended to use whatever was on hand. The signal carrying caps are important too. Many debates have taken place, but the most agree that OD 715's are harsh and should be avoided for the most part. 6PS ODs are better suited and I've had good success with Xicon MPP.

Of course I'd heard about the Dumble amps.....but never played or listened to one until recently via an internet comparison over my Bose spks. As a minimalist I'll need to compromise on the relay and extra gain stages to get a better OD "Tone".

There's a lot of great info hear. Thanks for the input.

Many folks have taken the minimalist approach with the extra features. Personally I like having the relays and footswitching on OD and PAB at a minimum. THe jazz/rock switch is pretty useless as is the deep. Mid boost can be nice but not necessary.

Good luck with the conversion.