What to build ?

[Colas LeGrippa]

Hola amigos !


I have an old YBA1A (Traynor) from the sixties laying in my rehearsal studio, originally supplied with 6CA7 ( not the studio but the amplifier)that I would like to mod into....something else. I was thinking JTM45, JCM800.....but I want to keep the EL34's for sure. I need a fifty watter amp that I could crank to it s limit ( to my ears over limit 😁) with nice breakup. It doesn't have to be a Marshall, something built easily no reverb , no hassle  (now that Sluckey gave me his trick I dont need to get into time consuming rev circuitry).
Any idea welcome.


Colas

[66Strat]

My personal preference is for the JMP 2204. One of the best sounding Marshalls ever, IMO.

https://el34world.com/charts/Schematics/files/Marshall/Marshall_2204_jmp_master_volume_lead_50watt.gif

[PRR]

I would not molest a Traynor YBA1A.

If you want a JTM45, JCM800, get a JTM45, JCM800.

[Colas LeGrippa]

PRR, I know it's a shame, I wouldn't hurt an original  1964 amplifier of that class. But  it had already been modified many times....for the first time 20 years ago when I didn't know the diffrence between a power and an output transformer , when I joined this forum more or less.
Gee, buddy, you're giving me an idea....
I could modify it into a...YBA1A. The only mod I'd perform is separating the preamp k's and lower the pots value to 1 meg.


I'll seriously think about that.


Muchas gracias !


Coca Colas

[DummyLoad]

PRR, I know it's a shame, I wouldn't hurt an original  1964 amplifier of that class. But  it had already been modified many times....for the first time 20 years ago when I didn't know the diffrence between a power and an output transformer , when I joined this forum more or less.
Gee, buddy, you're giving me an idea....
I could modify it into a...YBA1A. The only mod I'd perform is separating the preamp k's and lower the pots value to 1 meg.


I'll seriously think about that.


Muchas gracias !


Coca Colas

that thing originally looked a lot like a 1959 marshall. save for the values of a few ot the parts, it's nearly identical, disregarding the LTPI and the grid-leaks of same. i'm with PRR, restore it as was to a YBA1-A MkII and i'd bet it sings very nicely.

preamp Ks are already separate and you'd be raising the volume pot values to 1M. ;-)  swapping to 1M pots will increase gain slightly. 

de nada!

--pete

[kagliostro]

I can only agree

Franco

[tubenit]

How about a Marshall but with a 5879 pentode in V1 for a FAT tone?

With respect, Tubenit

[Colas LeGrippa]

Pete, this amp had 4meg volume pots and tied k's originally. It migjt be older than what you think. Hablas español amigo ?
Thanks Tubenit, I heep your schematics in my future project files. I gotta use the parts I have in stock. I'm a poor lonesome guitarist .
Franco, you give me finally the guts to do it.


Have a good day !


Colas

[DummyLoad]

Pete, this amp had 4meg volume pots and tied k's originally. It migjt be older than what you think. Hablas español amigo ?
Thanks Tubenit, I heep your schematics in my future project files. I gotta use the parts I have in stock. I'm a poor lonesome guitarist .
Franco, you give me finally the guts to do it.


Have a good day !


Colas

colas, si, yo hablo bastante. viviamos en las islas canrias y fue a escuala español para primaria. 

back on topic, is it a MkII/YBA-1A, or the older YBA-1? the older YBA-1 had a funky bridged T filter between the summing amp and the TS driver. interesting that the TS was pushed with plate drive on the YBA-1. the YBA-1A seems to be more "guitar" friendly circuit - my opinion. tubenits' suggestion is also very interesting - i'd go with a EF86 though as it's still in production.

--pete

[Colas LeGrippa]

Ya me dijiste que has vivido en las islas Canarias, mii memoria hace falta jaja ! Disculpame.
It is a very old YBA1A according to the serial number. Early '60.
I might try the pentode preamp sooner, I'm so curious to hear what it sounds like.


Thanxxxx
Colas

[DummyLoad]

mi memoria hace falta, y tambien el mio. 

paz a ti hombre.

luego!

--pete

[Colas LeGrippa]

My good lord this amp's got tone !!!!!


Finally , I turned my YBA1A into a Marshall 2204, with some mods.


1. No tone stack but a tone pot.
2. No negative feedback.
3. Self bias instead of fixed bias. I don't need the
extra power of fixed bias and I find the K bias amps sound better.
4.No 47 pF between PI plates.
5. No low input, I ll never use it anyway.
6. Hi lo switch as a voltage divider with 68 k to gnd .


The rest is exactly the same, with voltages almost the same everywhere. I had to tweak the values of the supply resistors for that results, the power tranny is a bit different


I like the simplicity of the 3 controls: PRE volume, TONE pot and. POST volume..Don't need more to rock the halls.


I run the EL34's way over their limit without redplating. I ll see how many wees they will last...I ll lower the bias when I m broke hey hey !!!
Colas

[silverfox]

Ya me dijiste que has vivido en las islas Canarias, mii memoria hace falta jaja


Sounds more like Rastafarian, But then the Spanish were empire with colonies all over the world ja! Even the Canary Islands Mon.


silverfox.

[Colas LeGrippa]

Christopher Columbus and his friends killed millions of indians all over the world.
Asi fue el imperialismo. Ingleses and mucho más mataron a mmillones de inocentes tambien. Asi es el ser humano.

[Colas LeGrippa]

I think that the mojo of this design comes from the preamp cathodes. One 2.7k /.68uF followed by a 10k cold clipper that s all. No polarized caps. One could even swap the 10k by  a 33k cold clipper to experiment. In fact the design is so simple and works so well that  we can easily tweak the beast to fit our needs. The hammond 1650N hifi audio transformer that was already in there has guts..I would like to hear the difference from a Drake. Anyway I am very satisfied with this build and the result is better than what I was expecting
Colas



 

[shooter]

In fact the design is so simple

1st rule of engineering 

glad you got rid of the useless knobs and can focus on playing n grinnin 

[Colas LeGrippa]

We see things the same, Shooter. Less is more. I modded my Harley just the same

[shooter]

 
did the same with my jeeps, back seat - gone, wheel flares, out.  cd player that skipped 127time a minute over rocks-gone.  and that was on the one I bought new