Advice on Blues Breaker 2X12 type build

[bnwitt]

I'm currently finishing up a Hoffman AB763 4X10 SR type combo amp and after that I am going to build some 2X12 Marshall combo amps.  I will most likely make one of them a 1962 blues breaker replica.  I've been collecting period accurate boards and wire lacing among other things for the 2 board Tremolo version of the Blues Breaker.  That particular amplifier has a 2G374 germanium transistor in the Tremolo circuit Which are a little rare and I've noticed some other layouts which do not use that component.  The Ceriatone JTM45 is one.  Of course I want to build an amp that is tonally accurate to the holy grail Blues Breaker amp but also that is serviceable and not use components which are hard to find and that may disappear all together in a few years.  I don't imagine the transistor is all that critical to the tone anyway.  Also, the tremolo in the Blues Breaker is not well regarded and I'm wondering if anyone has replaced it with a bias vary version.  Or is there a preamp power section version of the amp without Tremolo that others have constructed that has the original tone.  So, I'm looking for a proven layout from which to build a Blues Breaker type amp if someone has one rather than starting from scratch from the photos.  Any advice is appreciated
Barry

[terminalgs]

That particular amplifier has a 2G374 germanium transistor in the Tremolo circuit Which are a little rare and I've noticed some other layouts which do not use that component

See this thread for more about the 2G374 in that circuit: http://el34world.com/Forum/index.php?topic=7261.0

[PRR]

> a 2G374 germanium transistor in the Tremolo circuit ... I don't imagine the transistor is all that critical to the tone anyway.

Sadly, it probably is. Not the exact part number, but a Germanium PNP of similar size (current rating) and gain (hFE).

Small Bear Electronics is the go-to for audio Germanium.

Not much data on 2G374. No great stress here. I might use a socket and try one of SB's random assortment packs. Also make the resistor divider to the transistor Base somewhat adjustable.

[mresistor]

Barry  - to me the Ceriatone layout looks good and with the bias vary tremolo I bet it sounds killer. Notice it has a red led in there. I've never heard one though, all I know is Ceriatone seems to have a good reputation. I think with the right iron and some more expensive capacitors to duplicate the mustard caps and such it would have that vintage sound. Wasn't the '62 bluesbreaker with tremolo a 30 watt amp using 5881's? Or was there two variations?
I did notice that a Hammond 290LX is quite spendy, but still at least $100 less than a Mercury.  I know there are cheaper options American made, I would think the OT would be the most critical. There
are these and I'll bet George is the guy to talk to.  https://store.metropoulos.net/collections/transformers

[bnwitt]

The original, and the one I'm interested in, had KT66 power tubes.  I agree the Ceriatone layout looks like a winner.  The major down side to this amp is the cost of the transformers for sure.  I've got to sets of MM 50 watt trannies in stock so I may go in a different direction than the BB just because of that but I guess I could sell a set of the MMs to pay for the BB trannies

[tubeswell]

...Also, the tremolo in the Blues Breaker is not well regarded and I'm wondering if anyone has replaced it with a bias vary version.  ...

A vibro-camp style LFO with a buffer output that wiggles the cathode bias on V1 might work well (if you don't want to wiggle the output tubes). I haven't tried this in V1 of any amp yet, but it has a nice smooth tremolo (but I have used it on a V2 stage previously, so I can attest to that).


Edit: Some more blues breaker info attached FWIW

[TIMBO]

This is my effort......

[purpletele]

This is my effort......

Timbo,

That is a very nice and unique cabinet.

Is there an amp in the top section? 

[TIMBO]

Hey purple, Just a variant of the BB cab.

[bnwitt]

Very nice work gentlemen!

[purpletele]

Hey purple, Just a variant of the BB cab.

Timbo,

I like that cab!


Nice work the entire amp looks great.

I have never heard of those speakers are they a British Mfg?

[TIMBO]

Hey mate, They are local built in Australia, been around for many years.
http://www.etonesound.com/

The ones in my amp are about 50 years old, sound awesome.

[DummyLoad]

That particular amplifier has a 2G374 germanium transistor

25V, 150mW, PNP, hFE = 60. 

http://www.smallbear-electronics.mybigcommerce.com/low-gain-germanium-pnp-60-to-69-bag-of-5/


http://www.nteinc.com/specs/original/2N404.pdf

--pete

[purpletele]

Hey mate, They are local built in Australia, been around for many years.
http://www.etonesound.com/

The ones in my amp are about 50 years old, sound awesome.

That's impressive!