Looking for circuit of SE amp. for Eimac 100TH

[udonbkk]

I just got 100TH tubes and looking for a sample of good Single End Amp. Try to search around but non are really give good detail. I don't mine if it will drive with Mosfet or transistor.

Any one ever build one or where I can find those info.

Thanks.

[Tweeker]

100TH datasheet. The section on AB2 AF amplifier and modulator gives some PP operating points. It looks like youd need alot of grid drive for A2 SE.

The 810 is the most similar tube I can think of, 811 has some similar characteristics too, look to amps using those for a general idea.

100TH is a high mu triode intended for use with grid current, so will need some sort of power grid drive, like a mosfet source follower or interstage transformer. It wants a fairly high impedance load too.

[Wavebourn]

The simpliest way is to use it with couple of output transformers, one of them connected reverse to grids, bias on the center tap, and a speaker coil of it is drivewn by a solid state power amplifier.

[astouffer]

Found this one just laying around...

[rcavictim]

Originally posted by Wavebourn
The simpliest way is to use it with couple of output transformers, one of them connected reverse to grids, bias on the center tap, and a speaker coil of it is drivewn by a solid state power amplifier.

Wavebourn is right. I`ve used that technique and clip leads on the bench for years to `play` with xmitting bottles in audio output applications. As stated was for P-P and the reversed o/p xfmer becomes the phase splitter but same deal works for SE.

For drive maybe George`s Powerdrive FET circuit from Tubelab is the ticket.

[rcavictim]

Originally posted by astouffer
Found this one just laying around...

Voltage doubler Hi B+ supply. BOO! Anyone making an amp around a 100TH wants to look at glowing glassware. Supply schematic can easily be tailored to suit.

[udonbkk]

Thanks for the info. this is really helpful.

I will have to modify a lot and may be I will use Switching Power supply to light up the fillament. 10 Amp each transformer is really big. I try to keep the total weight minimum. Any sample of Mosfet circuit to see.

[coresta]

I'm working on the same idea but i'm reluctant to go higher than 700v /100mA (my PTr and OTr do not carry more than 100mA) . So, it' ll be working DARK PLATE , and not RED DULL . Is that a problem ? (no gettering of the vacuum ) . Any idea ?

[Ed Sawyer]

They (Eimac triodes) work fine w/o running red or orange plate color. I run 75TH's at a dark plate level (400v @ 25ma or so) and they don't seem to be any issues.

-Ed

[coresta]

How much power do they / it last ? SE or PP ?
How long did they work "dark plate" ? A2 or A1 mode ??!

cheers