High power Tweedle Dee.

Overdrive Special, Steel String Singer, Dumbleland, Odyssey, Winterland, etc. -
Members Only

Moderators: pompeiisneaks, Colossal

Post Reply
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

High power Tweedle Dee.

Post by MHProd »

Happy new year to everyone!!

Thank you Charlie Wilson for posting the amp's pictures and everyone else who contributed.

I'm rounding up the parts for a high power Tweedle Dee (cathode biased KT66s) and I wanted some second opinions on the transformers, mostly the OT.

Power: Bassman PT 354V 250ma. Planning to use a 5UG4 recto which should keep the B+ around 425V on the plates.

Output: I'm hesitating between 2 OTs I already have. A Pacific TW Express OT (the ones sold by RJ). I was planning on using the 6K6 primaries but I guess I could use the 5K2 taps instead. OR I could use an original Dynaco 470 which has 4K3 primary impedance.

When it comes to OTs, I tend to favor original/vintage iron if available.

Any thoughts?
fenderbender
Posts: 21
Joined: Sun Feb 13, 2011 6:04 pm
Location: Denver

Re: High power Tweedle Dee.

Post by fenderbender »

'Sounds like either one of those would work really well. If you don't mind spending the extra $ This could also be an option: http://mercurymagnetics.com/images/tran ... 45RS-L.pdf
$276 list is not exactly cheap, but if I had the money I'd spring for one of these.
Tom
(No, I'm not affiliated with MM. :lol: )
It sounded so sweet... And then it caught fire!
fenderbender
Posts: 21
Joined: Sun Feb 13, 2011 6:04 pm
Location: Denver

Re: High power Tweedle Dee.

Post by fenderbender »

I have had really good experiences with Dynaco iron as well. Both the A470, A430/431. I've restored and hot rodded Dynaco St.70s and MkII's and MkIII's. I've used the A430 in a crazy Fender Champ, that I turned into a Mesa style Simulclass power amp in, running EL34's and 6550's.
Can't get much better iron than that!
It sounded so sweet... And then it caught fire!
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: High power Tweedle Dee.

Post by MHProd »

Thanks guys.

I've never liked the sound of Mercury's iron for some reason... Always sounded stiff and bright to my ears.

I'm mostly trying to figure out what would be the best impedance for the KT66s.

I have 2 original 470s. One will go in a Rocket and I was planning on building a TMB 36w style head with the second, but maybe it will work well with the Tweedle Dee.
User avatar
rogb
Posts: 1078
Joined: Fri Apr 02, 2010 9:56 am
Location: London, England

Re: High power Tweedle Dee.

Post by rogb »

MHProd wrote:Thanks guys.

I've never liked the sound of Mercury's iron for some reason... Always sounded stiff and bright to my ears.

I'm mostly trying to figure out what would be the best impedance for the KT66s.

I have 2 original 470s. One will go in a Rocket and I was planning on building a TMB 36w style head with the second, but maybe it will work well with the Tweedle Dee.
I never really bonded with my Tweedle Dee so I changed the iron to Hammond 291CEX Vibrolux 207 mA and 1760J 40w Pro 4-8-16 and tubes to 6L6. Also a 5U4GB rectifier.
I use it a lot now :)
User avatar
ToneMerc
Posts: 3480
Joined: Sun Apr 26, 2009 3:55 pm
Location: East Coast

Re: High power Tweedle Dee.

Post by ToneMerc »

The two that I built, I used MM Tweed (6k) Pro iron and 5881 glass.

TM
RB
Posts: 126
Joined: Thu Apr 06, 2006 11:36 pm
Location: San Diego CA

Re: High power Tweedle Dee.

Post by RB »

I have built/converted many Tweed Deluxes to big bottle amps. Tried all the OTs Mentioned (except MM) above
and settled on the Tweed Pro/Super/Bandmaster 6k iron.

6L6,5881 and KT66 all sound amazing cathode biased. Fixed bias produces a little more power but some of the
creamy quality disappears. I have never used the MM version but use the Mojo/Heyboer and the Mag Component versions.
Both equally good. I use the Allen 180mil PT that fits the tweed chassis. I think it is the TP40D.

Once you go this route it's no longer a 5E3. It becomes a Tweed 30+ watt with a slightly dysfunctional tone stack.
Just about every client eventually asked if I could do something about controlling the levels and getting more cleans.
My solution was to convert the input section to a brown deluxe and use a dual pot for the tone control.
You basically end up with a small Tweed Super kind of an amp which is not a bad thing in my book.

Good luck with your build and have fun

Regards
Randy
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: High power Tweedle Dee.

Post by MHProd »

Thanks everyone ! Looks like the 6K6 tap of the Pacific out should be just fine.

Still waiting on a few parts. I'll be using some special components which worked really well in a previous build.

Very curious to see how it sounds. A little surprised to notice many builders were left rather unsatisfied with the regular Tweedle Dee...
User avatar
ToneMerc
Posts: 3480
Joined: Sun Apr 26, 2009 3:55 pm
Location: East Coast

Re: High power Tweedle Dee.

Post by ToneMerc »

MHProd wrote: A little surprised to notice many builders were left rather unsatisfied with the regular Tweedle Dee...
I'm not really surprised, your mileage may vary though.

I built the Tweedle Dee and the Dumble layout Champ because like many here I'm a fan of HAD's work. However, a little pixie on my left shoulder kept telling me it's just a hot biased Tweed Deluxe with heavier filtering, IMHO he was right. I do slightly prefer the big bottle version over the 6V6, at least in my setup. Overall, it's cool for what it is, another tweed tonal screwdriver in the tool box. For a small go to amp, I like the 6g3 I built with 40W iron and the 5881 better.

TM
stephenl
Posts: 381
Joined: Wed Aug 13, 2008 10:21 pm
Location: Clinton, MA

Re: High power Tweedle Dee.

Post by stephenl »

KT66's sound great with 8K primary - ala JTM45

390v Plates
275v Screens
Rk = Shared 250R w/o Bypass cap
Po = approx. 30watts nearly Class A

Sound = warm, tight/percussive bass, decent amount of chime

I used a Marstran JTM45 OT (103 I think)
Steve
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: High power Tweedle Dee.

Post by MHProd »

I think I have a spare Marstran 103 somewhere... I might try.

I was thinking 180ohms with 22uF for the shared cathode.

Right now I'm working on the board and waiting for the PT.
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: High power Tweedle Dee.

Post by MHProd »

All right, I'm about halfway done. I settled on the Pacific OT after all, 6K6 primary.

A couple of extra mods:

-NFB switch (27K to 16Ohms tap)
-Marshall style 2nd chanel (2K7/.68uF and .0047uF cap)
-Conjunctive filter on the OT primary. I do this on all my builds. Helps with oscillation and sweetens the top end a tad. In this case it will be 8K2/4700pF.

Have you guys found it useful to put a 1M grid stopper on V2 to reduce blocking distortion or do you think Dumble's mods took care of that?
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: High power Tweedle Dee.

Post by MHProd »

Finished the amp today. I installed 470R screen resistors and 10K screen grids.

No blocking distortion whatsoever and the amp is very quiet, tone is thick and low end is tight but not too tight, just enough to keep the mud away. The PI trimmer seems to adjust the attack. It is set almost all the way counterclockwise.

One issue: The amp sounds dark... Even with the tone control on 10. No air on top... It doesn't breathe. Imagine a presence control set to -5!

Unfortunately, I only have a 4x12 (early 70s Marshall with greenbacks) right now, no open back cabs. That's probably not helping the amp to breathe but I doubt it's the issue (I could be wrong??).

I checked the B+ and with the 5U4, I got 380V on the plates (KT66). I expected something a bit higher. I tried a GZ34 and the plates went to 408V.

Played the amp some more and it sounded more alive. Still muffled but better. I checked the bias and turns out I was WAY over... I had 2 330R in parallel and the tubes were dissipating 30W!! I took out one of the cathode resistors (now 330R) and got the B+ on the plates to rise to 434V (23W dissipation). The amp still sounds muffled but now it doesn't sound as good... I get some light ghosting, thinner sound and a bit of blocking distortion... I'm thinking of trying a pair of TAD 6L6WGC I have (tubes rated at 30W).

I'm not sure how to get the amp to sound less congested and more open... Any suggestions would be greatly appreciated!
MHProd
Posts: 167
Joined: Tue May 07, 2013 6:47 pm

Re: High power Tweedle Dee.

Post by MHProd »

Anyone?
Post Reply