Princeton Dumble

[mrdarwin]

Hi there!
I plan to build two favourites amps in one: a Dumble ODS preamp section added to a power section of a Princeton Reverb with 6v6, bias tremolo and tube reverb.
Is there anyone who did this? I found some infos about 6v6 powered Dumble, but any about a combination of ODS and princeton...
Do I miss something? Is it possible? Still looking and reading threads...
thx

[martin manning]

I don’t recall seeing exactly what you are proposing, but it looks straightforward. You’d just replace the PR preamp with an ODS preamp, leaving the rest as-is

[mrdarwin]

That's exactly that I want to do Martin.
But I'm asking cause I didn't find anyone who did this... perhaps it has been yet tried with bad results and that's not popular...

[martin manning]

I don't see any reason that it wouldn't be successful. I would modify the power supply a bit, creating a separate branch from the unused filter node. That would feed two new nodes, which would have the correct voltages for the Dumble preamp.

[10thTx]

Deleted

[norburybrook]

Hi there!
I plan to build two favourites amps in one: a Dumble ODS preamp section added to a power section of a Princeton Reverb with 6v6, bias tremolo and tube reverb.
Is there anyone who did this? I found some infos about 6v6 powered Dumble, but any about a combination of ODS and princeton...
Do I miss something? Is it possible? Still looking and reading threads...
thx

anything is possible Having made quite a few ODS amps I'd say this: the reason they sound like they do and work like they do is because the pre amp section feeds an output section that holds together musically. It's one of the few amps where the master volume really works well. fender amp tends to start to fall apart when dimed, because there's too much bass frequencies, the output section is driven into overdrive too and if you're not careful the sound just falls apart.

In comparison the ODS filters out the unneeded low end and the filtering and diode rectification means there's little sag and a stiff power amp which will hold up and reproduce the overdriven tones from the pre amp into your speakers at high levels or low.

I set up a 50w #102 against 2x super reverbs and 2x deluxe reverbs, so 4 amps all dimed and connected together( it was my friends touring rig), and the 50w Dumble held together better than those 4 amps.

So my point; No reason not to build this amp but it's kind of going against what the ODS design and ethos is. A princeton will give you great overdrive at a low level if you dime it and stick a decent drive pedal in front of it anyway

it's all up for grabs though and you may love what this amp does when you build it, which is all part of the fun.

M

[martin manning]

Dumble tone is all in the preamp, which is coupled to a robust and clean power amp. For low volume use I think this D-PR hybrid would work fine, and have the reverb and tremolo effects added to the mix. Overdriving a cathodyne is never good, but within reasonable bounds it would perform well, staying clean and balanced. Works in an SVT ;^)

[Tony Bones]

To help with the discussion of this idea. DRAFT

There is an editable ExpressSCH version attached also.

With respect, 10thtx

Do you think that the OD section should be inside the NFB loop?

[10thTx]

Do you think that the OD section should be inside the NFB loop

I have NO idea. I simply drew up something for people to begin a discussion on and hopefully edit where needed.

10thtx

[10thTx]

Given Marcus's well thought out comments about a stiffer power supply, solid state rectification etc...……

How about using a solid state rectifier & increasing the first two filter caps to 40uf to add some stiffness.

Then using a reverse 12DW7 where 1,2,& 3 are 12AX7 like for the vibrato and 6,7, & 8 are 12AU7 to keep the phase invertor with lower gain and then adding 10k grid stoppers to the 6V6's? Maybe this would keep the power section cleaner and help a little bit in the right direction?

I am NOT saying this would work, but perhaps it might lessen the short comings of a PR phase invertor and B+ rail?

It could be a "good sounding" amp at lower volumes with some dumblish flavoring to it. I don't think it would sound like 102,124,183, etc.....

Thoughts?

With respect, 10thtx

[didit]

Hello --

This thought is on my build list, with caveats. Princeton chassis and transformers, probably output upgraded. Silicon diodes & forego tube rectification. Stiffer filtering (60-40-20-20) & a 4H choke. Using all four sockets -- first two are preamp & OD, next is active-loop-alator and finally a squeaky clean LTP PI. Volume, T-M-B, OD & Master. Presence on the back. And 5V winding provides relay's supply.

Experience. My two favourite Princetons are modified from stock. One has cathodyne, but several tweaks to improve it; the other an LTP consuming tremolo triode. Perhaps not quite correct, but each to one's own interpretations. Need more tinkering time with variations on Dumble's OD preamp before tackling.

Best .. Ian

[martin manning]

I was going to suggest that the known PR PI mods might be a good idea. Another idea for the power supply might be to add a DR choke and make it look more like a down-sized ODS power supply.

[didit]

Confident, after having spent many hours tinkering with Princetons, that the stock PI is the weakest link; and certainly contrary to goals of clean power.

[Tony Bones]

I think a Deluxe Reverb output stage would perform well. In the end, just build an ODS with 6V6 power tubes, but pay attention to max B+ of course. I've heard that JJ 6V6's can handle pretty high plate voltage.

[norburybrook]

I think a Deluxe Reverb output stage would perform well. In the end, just build an ODS with 6V6 power tubes, but pay attention to max B+ of course. I've heard that JJ 6V6's can handle pretty high plate voltage.

or just stick a good drive pedal in front of the Princeton. Robben ford quite often uses his Zen drive these days and keeps the #102 on the clean

I can understand the allure of the spring reverb and trem, it's the two things I use most but there's probably a good reason you don't see these on an ODS.


Strymon flint sounds great but doesn't work in the front of and ODS when using the OD. You need to use a dumbleator/Buffer in the loop as it knocks off some high end even though it can take the levels.



M