• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Looking for circuit of SE amp. for Eimac 100TH

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 said:
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.


2006-09-30 3:52 am
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.


2009-01-09 3:02 pm


  • RW40-9-english.pdf
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2009-01-09 3:02 pm
I attempted to replace TANGO XE60-5snf with SOFTON RW-40-5 OPT on my 811A amp and
it was known poor performance observed particulaly in lower frequency range.
Though I do not understand why its happend such difference(refer to #13)
SOFTON refund the money to me, but it is my regret that SOFTON did not respond me with comprehensive explanation sofar.