851 set?

[pleiades]

I am mostly kidding, since I'm not exactly sure where I'd scrounge up a 11V 15.5 A supply for the heaters and keeping 2 kV sitting around the house for the plate isn't the greatest of ideas...

...but I recently found a (NOS as far as I know) JAN GE 851 triode in my attic, and the rated 600W (for AF class A) plate dissipation screams "mono amp so powerful my speakers would never forgive me."

Anyone done anything remotely similar?

[Miles Prower]

The A Number One challenge to a project like that is going to be the OPT. SE OPTs require a core gap to avoid DC core saturation, and for anything over a couple dozen watts becomes a formidable challenge to get it right and to get it sounding good. (I once had a design for a SET that used the 812, but Jack at Electraprint couldn't guarantee that the OPT would function as a HiFi OPT, so I ditched that idea.)

Not that it can't be done, and there have been some pretty insane SETs built with such high powered triodes. You might want to search for 833 SETs. (Tubelab did some experimentation with these.)

[danFrank]

Hi, Electra-print used to sell (maybe still does) a SE transformer for the Eimac 304TL triode. Rated at 5K primary at 300ma. I don't know if it's rated for the 2-2.5KV B+ that the 851 needs to sing.
I thought about using this tube back in the late 80's when I was young and dumb and full of ..... You get the picture.
It's a VERY impractical project but can be done. Filament hum will be a major problem because of the 11 volt 15.5 amp rating of the filament, but the 851 tube is relatively easy to drive for a class A1 triode because of the mu of 20; easier to drive than the 845.
Anyway, I collected the tubes for the project, wound a filament transformer out of a torroid core that I had, but never saved up for the output transformers; I had other habits that needed supporting at the time...
If you decide to build, good luck, but you can build something that will sound better for way cheaper.
Daniel

[kavermei]

Don't fall into the trap of thinking 'I got the tube for free, might as well build an amp around it'... In the end, the tube is an insignificant part of the cost.

Are you sure you need the power? Because as said, there are lower-power options which are both better & cheaper.

Kenneth

[pleiades]

I do not need the power, and I am not planning on building anything with it in the near term, (since sourcing iron for it would be both difficult and expensive) I was just curious as to any experiences others might have had. When my grandfather gave it to me (years ago) he said it was a rectifier so I haven't looked at it until now. My original plan was to mount it in the chassis of a SE 6L6 stereo amp I'm building (unconnected) just for aesthetics, but I couldn't help digging up a schematic.

I figure that having an unconnected tube "just for show" is acceptable in an amp that doesn't contain any sand.

[AJMARS]

I'm currently working on a 851 100W SE amplifier project

Mainly the Power supply will be 2000V
The filament supply will be AC or regulated I will test both
The first stage of the amplifier will be done with a E80L pentode

The amplifier (mono block) will have four distinct parts
1 - for the main power supply (4U 19", housing a Variac for soft start)
1 - for the filament 11V 15 Supply (3U - 19")
1 - for the "auxilliary" supplies (First stage, négative, filaments.., 2U 19")
1 - for the tubes and the ouput transformers (2U 19")

The output transformer will be a Plitron 20 cm diameter 5 kohms "Special design" series
The supply transformers has been done by Heacom (French company) under specifications

.....

Funny project (but heavy)

André

[AJMARS]

a 851 on my right hand, a 211 on the left one...

Andre

[Brit01]

I can imagine my wife's face coming home with that one day!!
I seeing the electric bill!

Now that's a valve!

[AJMARS]

Oh..... My wife is really cool.... she is more curious than hostile....
My daughter (10 years old) is very interessed.... The cat is not really happy, he doesn't understand why I did remove the red fish inside the aquarium and replace it by a plate.....

Andre

[kavermei]

Holy smokes!

Compared to that, the tube in my avatar looks like a transistor