TWEEDLE DEE SINGLE CHANNEL + TREMOLO

[fred.violleau]

Hey guys,

Another Tweedle Dee build is on the way!
I want to assemble :
- a single bright channel
- with cathode bypass and NFB as provided on Rob Robinette's website (I love this feature that really extends the palette of the 5E3);
- Dumble PI cathodine (with Lar Mar type II Master Volume and 470k grid stopper) ;
- Tremolo ala Fender 1164 (but one triode only)
- adding a bias supply ala Princetone;

Here is the Schematic I put together:

Tweedle Dee + Harmonic Vibrato Schematic.pdf

Let me know if you see any error, I should start my build next week, turning an old Symphonic Electronic Corp tube amp into a rock machine !

Thanks again
- to Charlie Winston for providing the schematic of the Tweedle Dee,
- to Rob Robinette for the many explorations and tweaks provided on his website,
- to this great community sharing generously its time and knowledge with fellow apprentice like me !

Fred;

[fred.violleau]

Here are a few pics of the donor Symphonic amp.

Originally a stereo tube amplifier with single ended 6V6s, tube rectifier, two 12AX7 and a third smaller tube for tremolo.

Probably 2 x 5 watts output judging the size of the small OT.
3 inputs and a pair of RCA jacks as speakers outputs.

PXL_20240819_231848855.RAW-01.COVER.jpg

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PXL_20240818_134557906.RAW-01.COVER.jpg

I plan on reusing the PT, tube rectifier and 6V6s into a push pull configuration with a single 5E3 Hammond replacement output transformer.

The tube layout gave me a little headache with organizing the components layout. And after a few iterations I have settled on a SSS style For the preamp.

[fred.violleau]

Been moving slowly but got to get together the preamp board

PXL_20250518_204042140.RAW-01.COVER.jpg

And finishing the heaters as the donor would not leave me many options

PXL_20250518_204008470.RAW-01.COVER.jpg

Ran out of eyelets for the power amp board, order is on the way

PXL_20250518_204125035.RAW-01.COVER.jpg

Cheers;

Fred

[fred.violleau]

Amp is finally all wired up !

The build process was challenging as the tubes layout is not ideal to manage efficiently cable runs.
Hopefully the amp will remain quiet.
I have used a known grounding scheme that worked very well in my previous Tweddle Dee builds.
The remaining questions is : will the tremolo work as intended since I removed one triode (will it impact signal strength or not)?
Waiting on the faceplate that should arrive tomorrow;

Power supply :

IMG_0150.jpg

IMG_0152.jpg

And final build :

IMG_0203.jpg

Now let's iniate the tests;

Fred.

[sluckey]

That bias vary tremolo should work just fine with 6V6s. There's one small error on the schematic. You show 6V6 cathodes connected to the bias voltage. Should be connected to ground (maybe through 1Ω resistors).

[fred.violleau]

Hey sluckey,

Thanks for catching this one !
Yes the cathodes are connected to ground with a 1ohm resistor;
Vibrato is working indeed.

Smoke test went well, nothing burnt or smelling wrong;
Voltages are good but on the bias;

I have sound but it feels like I have not enough negative voltage.
Will try and sort it this week;

Fred.

[sluckey]

I have sound but it feels like I have not enough negative voltage.

I have three fixed bias pp 6v6 amps. Bias voltage on all is -36V on pin 5. This gives about 24ma to 26ma cathode current. Amps sound great. The Harvard power section looks very similar to your power amp.

https://sluckeyamps.com/harvard/harvard_5f10_schem.pdf
https://sluckeyamps.com/tdr/tdr.pdf
https://sluckeyamps.com/6v6plexi/6v6plexi.pdf

[fred.violleau]

Hey Sluckey,

Thanks for all the input, I trully appreciate your help;

I found the culprit : wired the bias feed of the rectifier tube ... but after the protection diode;
No wonder I found the amp was missing bias : there was none !
Lucky me is using worn out tubes for all my smoke test... just in case ...
At least I did not damage new set of tubes!

The sweet goodness of that harmonic trem is an absolute delight!
Added a high \ low input selector, just to give some headroom with hotter pickups;
These little beast really have something special;
I tried to use a tilt instead of the usual tone knob and I find it very usefull, offers a wider palette of sounds;

I will try to record something next week;

Cheers!

[sluckey]

The sweet goodness of that harmonic trem is an absolute delight!

It's not harmonic tremolo. It's bias vary tremolo. Harmonic trem (vibrato) is much more complicated and has an even sweeter sound. See Fender 6G12...

https://el34world.com/charts/Schematics ... t_6g12.pdf

[fred.violleau]

Yes indeed Bias tremolo.
Now you got me curious to taste the harmonic tremolo
Thanks again for the support, and this great community;

Fred.