12B4A tube amplifier with output transformers

[Original Burnedfingers]

Hi

I have looked thru the forum trying to find a PP 12B4A amplifier that uses output transformers. NO, I do not want the transformerless version that has been floating on the web.

Please post any interesting ideas as I have heard the 12B4A is a distant cousin of the 2A3 tube.

Thanks
Joe

[Fuling]

12B4A, my favourite pet!!

Unfortunately I´ve never tried them in a PP amp but I´m sure they´ll perform fine. Give them nice transformers and driver stages, they deserve it

And by the way, be sure to mount them with the cathodes visible, since they glow quite nice.

[Brett]

Originally posted by burnedfingers
I have looked thru the forum trying to find a PP 12B4A amplifier that uses output transformers.

I've never seen one

Please post any interesting ideas as I have heard the 12B4A is a distant cousin of the 2A3 tube.

OTTOMH idea
OPT = 10ka-a
B+ = 200V
Ia = 28mA/tube
Rk = 420R // 100uF common to both tubes
Vg = - 21.5V

Driver is a diff or paraphase ECC99 with Hammond 156C as loads at 150Va and 15mA/tube.

PSUD a decent power supply.

[316a]

Originally posted by Brett


I've never seen one



OTTOMH idea
OPT = 10ka-a
B+ = 200V
Ia = 28mA/tube
Rk = 420R // 100uF common to both tubes
Vg = - 21.5V

Driver is a diff or paraphase ECC99 with Hammond 156C as loads at 150Va and 15mA/tube.

PSUD a decent power supply.

Op point looks good . I would use a 30VA 115+115/6+6 mains toroid as an output , secondaries paralleled to get a prototype going . 12B4a vary electrically , better to buy a bunch and match them up for PP , better still add variable grid bias and balance meters . A reference could be this schematic which uses a similar valve (beefier version:6CK4)

http://tinpan.fortunecity.com/saints...er/6ck4-pp.gif

Hope this helps

316a