Can this tube be used in audio amplifier?

[siliconray]

I got a FU-100F tube recently. I don't know what this big guy is used for. Seems to be high power short wave PA applications. Can this tube be used to make audio amplifier? Just curiouse, I don't think I will make such a huge amplifier.

[preludefan]

oh my god!

well..... im sure you could make an audio amp with it so long as it has a kathose, anode and a grid with which to feed a signal to, but the component values needed would be a mystery and weather or not it would sound good is also impossible to tell till you build it.....

[siliconray]

Well, the tube has only 4 pins, circuit is as simple as a transistor. But first of all, tell me how to make a 3000V DC power supply

[Yvesm]

Said to be similar with that :

http://frank.pocnet.net/sheets/088/4/4CX1000A.pdf

First at all find an adequate blower and all that hardware stuff necessary to force air flow trought anode fins !

I dimly remember that air cooling must be applied even with filament powered alone . . .

Good luck

[preludefan]

holy hell that is so powerful you could make a single ended otl stereo amp with just one on each channel!!! imagine the power!!! i want two of these now thanks to your link yvesm!
the quietest way to cool it would be to submerge the tube in a large container of cooking oil or similar, as oil does not conduct.... a microwave transformer connected to a high voltage bridgre rectifier should get you around 3kvdc....

look at this....we are on a roll already....


now- which driver tubes cold we use.... would a 6sn7 suffice?

[DF96]

This sort of valve can be difficult to tame: the surrounding circuit has to suppress parasitic RF oscillation and cope with occasional flashovers (internal arcs). Anyone who knew enough to do this successfully would know enough not to attempt it!

[ingenieus]

If you mount it on a wooden base, it would make a nice desk ornament or conversation piece.

[siliconray]

One guy not far away from me had made a amp with FU-250F successfuly, awesome power (more than 200W) and excellent sound quality. He put the tube in a oil tank to cool it.
I think RF oscillation and flashover won't be a problem with proper design for. But the high voltage and heat are difficult problems to deal with.

[siliconray]

This amp made by a DIYer in China is use the largest I've ever seen on audio amplifiers. It's FU-81, larger than a one liter bottle. The amplifier is over 50kg

[Miles Prower]

Originally Posted by siliconray

I got a FU-100F tube recently. I don't know what this big guy is used for.

It's a disk seal, VHF power tetrode. Probably good to 220MHz or better. Requires special mounting to contact the disks, the idea being to minimize the lead inductance when installing in a resonant cavity, or a T-line output resonator. You have to be very careful working with these types as the plate voltages are extreme, and the plate is external, so there's no glass between you and ~3.0KVdc.

Seems to be high power short wave PA applications. Can this tube be used to make audio amplifier? Just curiouse, I don't think I will make such a huge amplifier.

Yes, it can definitely be used to make an audio amp. However, getting a SE OPT that can handle the power while preserving sonic excellence is going to be a bit of a difficulty to say the least. (Get another one and design a PP around it is more "practical".) As for sonic performance, who knows? You might require local NFB to tame the tendency to make higher order harmonics (or not). This is definitely a try it and see situation, as the type was designed to far different criteria than audio performance. Specialized types can either be audio sleepers or real dogs.

Better still, if it's still good, E-Bay it and get more suitable finals for audio. VHF operators who do "moon bounce", DX contests, or try to reflect signals off comet tails will definitely be wanting that.