Leviathan \Le*vi"a*than\ (l[-e]*v[imac]"[.a]*than), n. [Heb. livy[=a]th[=a]n.]
1: the largest or most massive thing of its kind
2: monstrous sea creature symbolizing evil in the Old Testament

Heck, I don't think I'll ever get to starting work on this amp, but the idea... The giant amongst tubes, the GM100 makes even the 212E look like a sub-miniature tube. Whoah this thing is big, in every aspect. This tube was intended to be used as a 1000W transmitter tube, it has a 17V / 18A filament. You heard me right, 8-TEEN AMPS. Two wires of about 1mm diameter run down the center of the anode and act as filaments. The grid is a very thick wire (0.22mm?) set up pretty much like the 100TH and similar tubes. I imagine it will suffer from microfonics. Looks like the ultimate in power though.

If I will ever use this tube it will be in a mono chassis for my maybe sub-sub woofer (<40Hz). 

The operating parameters are absolutely lethal; 2kV and 500mA. Argh!!!


I made some measurement, although probably not much use. I stacked my two power supplies in series, 500Vdc and 350V dc; total 850Vdc/300mA capability. The mA needle didn't do much at this voltage. At 0V on the grid I got 105mA through the anode and 1mA through the grid. At these low voltages it is best to go A2, so I tried some settings here, all at 850V on the anode.

+5V: 120mA anode and 2.5mA grid
+10V: 130mA anode and 4mA grid
+20V: 160mA anode and 6mA grid

So this concludes that gm would be 30mA/10V = 3mA/V. This deviates from the text book parameters, but what woudl you expect at 1/2 the voltage and 1/4 the current. Bummer, no way of testing this monster with practical setting. The filament looks cool though!!! :)))

My transformer winder had a stroke today when I asked him to make an OPT and power transformer. Heh-heh, not the ussual 2W SE OPT here... Looks like some serious plans for this tube! Caps are on their way to me, 40uF/5kV yikes! Bias setting will most likely be in the region of 1800V/280mA (yes, 500W) to give maybe 150W class A watts. Maybe use it as preamp tube followed by my 437A poweramp??? Hmm... makes you wonder....

People around me are convincing me to build this amp, but for all the wrong reasons I think. I really haven't heard any questions on how it will sound, just: "how bright does it glow?", "how big is it?", "will the B+ cause sparks?",  "how much power does it use up without even giving off music?"... hehehe :)))

I may have found a good bias point for this tube after all. 2500V/200mA and -70V using a 10K load (Rp=2700). The grid can be driven to 135V (=270Vpp) before the tube clips on it's B+ supply (Ugrid = B+ / mu). This should give upward of 140W. For those not willing to go into grid current, it will still deliver 40W with 70V of swing. Run for three hours and you'll have generated enough heat to last the entire winter. Still, very cool tube, would love to build something with it.



Filaments lit to 5V so they can be seen without going blind.


I've seen the light!


The ussual comparisson to an ECC82 (hahahahahahah).
Size doesn't matter, eh?!


Full blast, 17V/18A !!!!
306W, and that's just the filament !


A better look ath the monster tube.


Just look at the mounting for the grid.


This gives a better comparisson for the size.
Notice the keyboard in back, to get an idea of the size.

Jim de Kort