Another Tweddle Dee !

[fred.violleau]

Hey guys,

Hope everyone is safe and sound these days, practising, soldering, and making the best out of these unprecedented times.
Last December, I found online an old beat up Pine Electronic Tube Amp, a bargain! I bought it and thought I could re-use the PT and OT and build a Tweedle Dee.
I set up a layout and added a few things based on Rob Robinette's experiences, and Charlie WIlson, ToneMercury, M. Fowler, Tony Albany and Marcus' testimonies, tweaking their own builds. Thanks Charlie Wilson for sharing this fantastic build with the ampgarage community, it is a real cool and fun one to build !

Changes from Charlie Wilson's schematic:
-chan1 would be a straight Dumble stage : 22k grid stopper 220k on the plate and 2.2k/5uf on the cathode
-Add a cascading/parallel switch that allows chan1 to cascade into chan2
-add a passive FX loop
-add a Pre PI Master Volume
-470R 3W grid stoppers
-add a Negative feedback switch ( V2A cap bypass/Off/56k NFB)

Used Orange Drops 6PS caps on this build, and I am preparing another build with 715 Orange drops caps only (I want to hear the difference

As the Pine amp had no rectification tube and was using diode rectification, I re-used the same topology, so I can keep voltages on par with what these were initially (B+1 was 364 v.).

I had fun putting together everything in a small 6 x 10 x 2 hammond Chassis, my goal was to make the amp as compact as possible. I need a Grab and Go amp that I can use with a few pedals, though this would be it!

First impressions on the build :
- soldering and assembling in such a tight space is a real challenge. It is even more difficult to service the amp if you need to do some maintenance (had replaced the 1M Local NFB with the MV initially and found out the hard way that it is difficult to debug a new layout once all the cable are hooked and that you trimmed these the exact length

Sonically, I must say this built goes beyond my expectations, it is really great, roars like beast. Agreed it is a bit bassy on a 2x12, and I want to try it with 10s to hear the difference. I am planning on ordering a celestion rocket 50 to try what Mr Dumble had in mind. I would say it is ideal for anyone playing Blues. I love the early breakup and compression to the sound.

A few remarks :
Chan 1, on it own is too bassy to be used as is
Chan 2 is much more versatile and interesting
Love the versatility of the feedback switch that allows this beast to breath hard (Chan2 + 0 NFB) or roar when I cascade chan1 into chan2 and bypass the V2A cap)
I though I would have trouble with the passive FX loop, but it appears it works extremely well. I am plugging a TC electronic reverb + TC mini-delay, and it sounds glorious!

PT is getting pretty hot after an hour or so... still can touch it though.
6V6 are getting really hot, like I cannot let my fingers on, else I get burnt

I need to build the head cab for this one, but I am in love already!

A few pics :

20200510_083100.jpg

20200509_104327.jpg

20200509_104259.jpg

Voltages :
Mains : 120 VAC
B+1 : 364,1VDC
B+2 : 359.6 VDC
B+3 : 317.5 VDC
B+4 : 300 VDC

V1 12AX7 (probably an old Sovtek)
V1A plate : 172
V1A cathode : 1.28
V1B plate : 186
V1B cathode : 1.138

V2 12AX7 (probably an old Sovtek)
V2A plate : 208
V2A cathode : 1.638
PI
V2B plate : 264,2
V2B cathode : 42.2 <= this one is almost twice as high than what CW had on his schematic...

V3 6V6
plate : 352.3
screen : 352
cathode : -21.48

V4 6V6
plate : 352.1
screen : 352.9
cathode : -21.42

[martin manning]

Very nice, Fred! Do you have a schematic drawn up? Maybe that will prompt some suggestions to get your Ch 1 dialed in.

[fred.violleau]

Thanks Martin, I will put together a schematic, and post here as soon as it is done!
Happy mother's Day!

Fred

[norburybrook]

Fred,


That looks great I love those small chassis, I've not been able to find them in the UK though.

I did a similar thing with ch1 on my amp, I used Bluesmaster values. I did fit a switchable cap though to kill some bass , i have the standard 0.022uf and some other value to cut the bass on a toggle, sorry can't remember what but works well.

I agree 100% about the NFB switch it really does make a for a good variety.

I think the 12 inch speaker is fine in a small enclosure like the original tweed deluxe. Remember the volume is quite small and it's very open . I made a more closed, larger volume 1x12 and with a humbucker on the neck(jazz) it's too much low end, hence my experiment with the caps.

After a lot of experimentation I settled on the Celestion Cream Alnico speaker.

I love this amp

be interested to see how a SS rectifier changes things.

My 6V6 tubes get hot..I've already gone through one Rectifier tube .... a lovely light show then ......bang.


Amp works well with 6L6's too. I had some of those Russian one's in there for a while. I think when the rectifier went it took one out.

congrats on the build


M

[ChopSauce]

Great!

I'm surprised to read about early breakup concerning this amp, though. You don't mind vs. a stock 5E3, do you?

[fred.violleau]

Found some time yesterday to put together an adaptation of CW's schematic.
It is not 100% proofed so beware!

If you see any mistake, please let me know!
I tried to illustrate all the changes with color and/or black boxes when changing values of some components.

Fred---Tweedle-D-Schematic.png

Also, i made a mistake on V1A and V1B input grid resistors and swapped the 22k with the 68k and since these are glued with silicone on the chassis... I can not change these anymore, but I will invert these on the next build.

@Marcus, Thanks for the kind words ! I Love these small chassis, a bit thin though, so I would not build a full ODS in these, but a small project like this one is a tight fit ! And 24$ a pop, it's a steal!

Agreed the NFB is usefull when I cascade channel 1 into channel 2, it tames the growling tone. I am not sure, but it feels like I would enjoy a little less NFB... I may use a pot on the next build! I have another Hammond Chassis, but a bit bigger this time, so I am shuffling this a bit so maintenance and the build would be easier..

I am curious about the value of your V1 bypass cap, because I may want to try and use something different so I can enjoy the two channels for what they have to offer

I have 2x10s in my Prosonic and I want to try and hook the Tweedle Dee to these so I can hear the difference. The trouble is, the cable coming from the speakers is so small that I barely can plug anything else but the Prosonic without putting at risk what I am trying to hook onto these...

I may not =need to warm up my music room when playing with this amp... I might get a heat gun just to measure the temperature of the 6V6 and the Power Transformer... Never had any of these going that hot before... BTW My voltages seems pretty much on par with what I was aiming for, exepted the PI.. any cue as to why?

@ChopSauce, I was looking for a ballsy amp with a tone that grinds without having my ears bleeding. I must say this one fit the bill (although it is quite loud too!). I really dig the Master Volume, it allows to dial Power Tube distortion vs Preamp Tube distortion, which is a nice feature....
As for what the original has to offer....I may have to build one to get to measure how different this one is !

Also : when I turn up both gain pots to 10 and MV almost full, the amp oscillates with the NFB switch on (super high frequency audible and annoying).

Thanks guys !

Fred.

[pompeiisneaks]

Found some time yesterday to put together an adaptation of CW's schematic.
It is not 100% proofed so beware!

If you see any mistake, please let me know!
I tried to illustrate all the changes with color and/or black boxes when changing values of some components.

Fred---Tweedle-D-Schematic.png
Also, i made a mistake on V1A and V1B input grid resistors and swapped the 22k with the 68k and since these are glued with silicone on the chassis... I can not change these anymore, but I will invert these on the next build.

@Marcus, Thanks for the kind words ! I Love these small chassis, a bit thin though, so I would not build a full ODS in these, but a small project like this one is a tight fit ! And 24$ a pop, it's a steal!

Agreed the NFB is usefull when I cascade channel 1 into channel 2, it tames the growling tone. I am not sure, but it feels like I would enjoy a little less NFB... I may use a pot on the next build! I have another Hammond Chassis, but a bit bigger this time, so I am shuffling this a bit so maintenance and the build would be easier..

I am curious about the value of your V1 bypass cap, because I may want to try and use something different so I can enjoy the two channels for what they have to offer

I have 2x10s in my Prosonic and I want to try and hook the Tweedle Dee to these so I can hear the difference. The trouble is, the cable coming from the speakers is so small that I barely can plug anything else but the Prosonic without putting at risk what I am trying to hook onto these...

I may not =need to warm up my music room when playing with this amp... I might get a heat gun just to measure the temperature of the 6V6 and the Power Transformer... Never had any of these going that hot before... BTW My voltages seems pretty much on par with what I was aiming for, exepted the PI.. any cue as to why?

@ChopSauce, I was looking for a ballsy amp with a tone that grinds without having my ears bleeding. I must say this one fit the bill (although it is quite loud too!). I really dig the Master Volume, it allows to dial Power Tube distortion vs Preamp Tube distortion, which is a nice feature....
As for what the original has to offer....I may have to build one to get to measure how different this one is !

Also : when I turn up both gain pots to 10 and MV almost full, the amp oscillates with the NFB switch on (super high frequency audible and annoying).

Thanks guys !

Fred.

Did you try swapping the OT leads? Usually with NFB and oscillation it means the OT leads are in the wrong phase and you're creating PFB not NFB.

~Phil

[ChopSauce]

Thanks for the reply and the schematic, Fred. I wish you'll have this Master Volume + NFB issue sorted soon ...

[fred.violleau]

@Phil even if the high frequency sound is really light ? I remember the loud squeal when the OT primaries are wired the wrong way, and it is not that sound. It happened on my previous build, and you can't play the amp with that kind of squeal. Whereas here, it is happening only at the very end of the master volume, like if I dial it down a notch, the high frequency disappears.

Fred.

[pompeiisneaks]

As I understand it ( and I've only had your experience of the really loud noise) sometimes in some circuits the positive feedback can be more subtle and just sound 'off' or slight instead of pronounced. It definitely can't hurt to swap the leads as a quick test. Especially since it goes away with NFB removed.

It could also be something in the NFB circuit itself.

~Phil

[fred.violleau]

Thanks Phil, I will try these over the long weekend. Just put a little recording so you get a glimpse of how it sounds. Live capture with the phone, and mistakes free of charge Let me know what you think, does it sounds characteristic?

My loose attempt at Tore Down House from S. henderson

https://www.facebook.com/709365999/vide ... 309786000/

Cheers, and thanks again to this wonderful community!

Fred.

[erwin_ve]

Hi Fred, I just listened to your Facebook clip and it sounds great. One of my favourite Henderson tunes.
There isn't much constructive to say on your build as I'm not into the Tweedle Dee (yet). It does look great and neat on the inside.
Thanks for posting!
Erwin

[didit]

Hello Fred --

Very nicely done. That's a true ship-in-a-bottle. Have you tried the 14"x6"x2" variant of those Hammond boxes? The extra length provides enough front panel for a full set of controls and input, and hangs well in a small tweed-style combo cabinet. Also built with slightly stiffer stock.

You are inspiring revisiting of whole 5E3 realm again. Tweedle Dee seems to actually work; whereas stock design build I did 15+ years ago had, to my ears, a narrow range of OK tone and was otherwise a blatty boom box with shrill breakup. It lasted just a few months before getting rebuilt into a 5E9 without the tremolo circuit, which is glorious still.

What's this Facebook thing of which you write? Says "must log in" ... and that's never going happen.

Best .. Ian

[fred.violleau]

@erwin thanks for the kind words! You should definitely explore the Tweedle Dee, as this build goes way beyond the blues tone I posted. I will try to post a new video showcasing all the tones I can get, it is a real beast, that goes from mild overdrive into JCM800 territories...

@didit , Thanks, it was a tight build! Funny thing is when I ordered the 10x6 Hammond Chassis, I bought a 14 x 6 x 3 in which I am planning to build my second Tweedle Dee. It will be housing a stiffer PT and OT and would allow to use 6L6s or 6V6s. I love the fact that there not many knobs to tweak so it's easy to dial in. The cascading gain is a real surprise to me and ads steroids to an amp that's already roaring.
Interesting comment on your build, because I was planning to maybe reverse the normal channel into a 5E3 stock bright channel, so I could get two flavour of the same fruit. I guess not

And about Facebook, that is where I posted the sound clip, I will put it on YouTube so you get to hear it as well.

Fred.

[didit]

Interesting comment on your build, because I was planning to maybe reverse the normal channel into a 5E3 stock bright channel, so I could get two flavour of the same fruit. I guess not

Made zero changes to the preamp stage when upgrading to 5E9. The key changes were: adopted directly the paraphase PI, reducing PI coupling capacitors to 0.02uF, and--if memory serves--tamed screen voltages a bit. Will possibly thread up on it as that amp is back on my bench getting some updates and small tweaks.

.. Ian