SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Vox and Hiwatt Discussion

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LuciMan
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SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by LuciMan »

Hi,

as buddy Karl is very busy at work so he doesn't have time enough at the moment to complete a few things on our projects (see Surrounded by Clones) I took my 1980 Supertwin (RM) I've bought last year. The reverb tank was missing and the sound didn't make me happy either.

This is how it looked after total surgery:

Image Image

I definitely wanted to use existing material like the NOS PT N50/1 (Engel) from the Sixties and the OT N503S (Socora/Radio Bourse) - a left-over from a 2x 6W amplificateur I made in 1963.
As schematic I used parts of the AC30 TB (NORMAL & BRILLIANT w/o VIB/TREM) feeding a EL84. To get the soft-start of a tube rectifier (EZ80) despite the fact the PT has only 1x 250V I added two 1N4007 to get a bridge-rectifier. Works perfect! :)

The original chassis has been supplemented with an aluminum profile bar so I had room for the tubes (ECC83 - ECC83 - EL84 - EZ80).

Image Image

All pots have the same function except Reverb VOL which became the NORMAL volume.

Image

The power supply will be changed a bit - I'm waiting for parts.

Image

Tomorrow I start with the wiring between the socket and the tagboard. There isn't much room so this will be a real challenge (for eyes & hands)! :mrgreen:

Mod edit: Fixed image links
Cheers
Claus
Last edited by LuciMan on Tue May 26, 2015 9:16 pm, edited 1 time in total.
tictac
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by tictac »

Why are you're leads so long on that one filter cap?

It looks sloppy and is less mechanically stable than a cap with properly terminated leads, more like the cap to the left of it.....

TT
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M Fowler
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by M Fowler »

Nice project I did the same thing on one of those SS AC4 cabinets it's now an AC15 sort of. :)
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LuciMan
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by LuciMan »

tictac wrote:Why are you're leads so long on that one filter cap? It looks sloppy and ...
Maybe you overlooked this ... :wink:
LuciMan wrote: The power supply will be changed a bit - I'm waiting for parts. ...
It will be done properly, but with this provisional PSU I was able to test the amp successfully this night when I completed the wiring.
M Fowler wrote:Nice project I did the same thing on one of those SS AC4 cabinets .....
I enjoyed doing this project very much - the costs were low and the amp sounds nice.
The only limitation are these small 5"- 6" speakers - I bet with the AC10 Twin combo i've got here it will sound "bigger"!

Cheers
Claus
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LuciMan
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by LuciMan »

Hi,

Here are some more pics ...

Image Image

Image Image

Image Image

The original wooden cover at the back won't be used - I'll build a two-piece AC30-like cover. The amp sounds lovely - just like a little AC30. No hum at all although everything is placed quite close to each other.

Mod edit: Fixed links
Cheers
Claus
Thomas_H
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by Thomas_H »

Wow, this looks awesome!
Would love to hear a sound sample!

This is one of my dream builds, I need to find one of those.

This must look awesome on top of a 2x12 vox cab!

Thomas
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tubelectron
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by tubelectron »

Fine job, LuciMan !

Your SuperTwin looks like to be the GrandBrother of my AC3 Top Boost :wink:

[img:640:480]http://img10.hostingpics.net/pics/303590IMG_3367.jpg[/img]

[img:640:480]http://img10.hostingpics.net/pics/669128IMG_3368.jpg[/img]

[img:640:480]http://img10.hostingpics.net/pics/148604IMG_3296.jpg[/img]

[img:640:480]http://img10.hostingpics.net/pics/557420IMG_3485.jpg[/img]

A sample, for sound comparison with yours :

https://soundcloud.com/tubelectron/vox- ... 12/s-45eI7

A+!
If it works, don't fix it...
www.guilhemamplification.jimdo.com
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tubelectron
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by tubelectron »

This must look awesome on top of a 2x12 vox cab!
@Thomas_H :

For my VOX AC3 Top Boost, smaller than the SuperTwin of LuciMan :

[img:640:480]http://img15.hostingpics.net/pics/191194IMG5967.jpg[/img]

A+!
If it works, don't fix it...
www.guilhemamplification.jimdo.com
Thomas_H
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by Thomas_H »

Tubelectron that picture is amazing !

it's like a little brother! And it sounds very nice.

Which speaker did you used in it? Is it too small to a 6" or 8"?
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tubelectron
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by tubelectron »

Thomas_H wrote:Tubelectron that picture is amazing !

it's like a little brother! And it sounds very nice.

Which speaker did you used in it? Is it too small to a 6" or 8"?
Thanks Thomas,

I used a NOS AUDAX / SIARE 5" speaker (ref. 12CPPA) that I had in stock (I should have bought more...) which is unfortunately out of production (since AUDAX / SIARE are out of business : a pity !). This speaker has a paper edge, an efficiency of 91.5db and accepts 20W RMS : a true marvel...

The battery switch selects : pentode normal mode, triode mode, pentode with treble attenuated mode.

A+!
If it works, don't fix it...
www.guilhemamplification.jimdo.com
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LuciMan
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by LuciMan »

tubelectron wrote:Fine job, LuciMan !

Your SuperTwin looks like to be the GrandBrother of my AC3 Top Boost :wink:
Thank you very much - your Escort-modification looks nice too. :)

How did you manage to realize the input stage & a top boost circuit with just one ECC83?

Cheers
Claus
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tubelectron
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by tubelectron »

LuciMan wrote:
tubelectron wrote:Fine job, LuciMan !

Your SuperTwin looks like to be the GrandBrother of my AC3 Top Boost :wink:
Thank you very much - your Escort-modification looks nice too. :)

How did you manage to realize the input stage & a top boost circuit with just one ECC83?

Cheers
Claus
Thanks Claus,

I called my amp AC3 Top Boost as a :wink: to its big brother the AC30 Top Boost (I had a 1976 model), but it has nothing to do with the Top Boost official circuit, it only can duplicate some of its well-known tone settings.

I think that I may have already posted that schematic some years ago on the forum, but here it is again :

[img:640:450]http://img10.hostingpics.net/pics/66860 ... ematic.jpg[/img]

I wanted to do the same as yours but with a reverb but I didn't found such a well preserved SuperTwin as yours, so I discarded the idea...

A+!
If it works, don't fix it...
www.guilhemamplification.jimdo.com
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schaublin65
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by schaublin65 »

Hi,

thanks for posting these really cute amps.

take care..

John
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LuciMan
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by LuciMan »

Hi there,

the AC3 TB SuperTwin did get a nice Upgrade last week! :)

After testing the circuit ...

Image

... I managed to get more space on the left by moving the four already existing valves to the right including the fuse around the corner ...

Image

... for an additional ECC83 using the AC4-VIB circuit. The ECC83-vib goes to the cathode of the first triode (NORMAL)

The existing tagboard was extended by the testing tagboard. The VIB isn't as strong as the AC15-AC30-VIB but very nice and the SPEED can be set very sensitively. Of course there is a foot-sw too..

There was no need to drill any hole for the speed-pot - replacing the SLAVE-jack socket gave the necessary place. The former slave jack-socket is now the foot-sw-socket (bottom).

Image

In the meantime my buddy Karl had built AC30-like rear panels (still waiting for identical screws ;)). The metal vents came from my AC30-Combo '78, which now has plastik vents (2 metal vents had to be replaced already in the past so now they look al the same).

Image

Mod edit: fixed links

Cheers
Claus
Thomas_H
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Re: SUPERTWIN (RM): converting from SS to a AC3 Twin Top Boost

Post by Thomas_H »

This thread keeps getting better...

You managed to squeeze one more tube in that tiny little amp!

If you can, please make a video. I would love to hear it. It looks awesome.

Cheers,
Thomas
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