In article ,
says...

Sorry for the top post, but here is the TL/TH deal

TL triode low gain, generally about 10
TH triode high gain, generally 40 to 100
Why the 304TL or 304TH, and not the others?? The 304TH is 4 75TH
triodes in parallel in one bottle, and the perveance is so far above
and beyond anything except perhaps a television horizontal output
sweep tube tetrode, or pentode. The sweep tubes probably won't have
enough dissapation unless you parallel them up.



What's the best tube type to use for a voltage controlled current sink,
with respect to linearity?

I am building plasma tweeters, with a DC glow discharge modulated by audio
(similar to US patent 4,219,705, but I'm using microhollow discharges
(MHCD) as cathodes for the larger discharge to remove cathode fall
instabilities; this technique was unknown during the time of that patent).
My power supply is 2700 V at 400 mA (200 mA for each of two channels for a
stereo setup), ripple filtered to 0.01 V. I'm hoping to have the discharge
drop most of the voltage, and the driving device a lesser portion. The
driver needs to be a voltage controlled current sink at the plasma cathode
(the plasma anode is the high voltage). Since the audio modulation is only
a few percent of the bias, less than 20 mA, essentially I'm concerned with
linearity in a small range around the average operating point. I need to
know what's the best tube type to use in terms of the sound quality, and in
what configuration (grounded cathode or grid, etc.). Most current drives
use pentodes, but I've been told a triode is more linear.

I got a pair of unused Y-434 (version of 4X150A with gold-plated grid)
ceramic beam tetrodes for $10 from eBay. Someone told me to drive them
grounded grid, similarly to this electrostatic headphone amplifier:
http://www.headwize.com/projects/sho...lmore4_prj.htm
I found cheap sockets, but no chimneys. Is it possible to DIY chimneys?
And what's the best approach to quieting the forced air cooling blower?