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Thanks, floobydust.

There are a lot of interesting points in you post to consider. What speaker you drive with your 2A3? If they are relatively high sensitively (like compression drivers) then did you consider going with a single stage? I think I have no power for my very high desirable load  in the tube that I use as my single driver  but  am still is debating of a more powerful IDHT tube in single stage application would be for me a better way to go then DHT two stages. (I am taking juts about driving a MF channel from 3.2kHz and up)  I think I would need 30W plate dissipation with 1K of plate impedance, or higher impedance and higher power and I will be able to employ such a tube.

I am not against DHT solution but it has a lot of intellectual ballast with it. Most stages, more cathode caps etc, etc. Then the coupling. The DC coupling is kind of freaky. Besides the subjects of stability it has strange impact to the lower region of sound. It is like you are thirsty and are drinking water but you have a large hole in the belly and the water run away from you do not letting you to be pleased with the satisfaction of the thirsty. The capacitive coupling has own problems. Leaving aside the fact the caps all have sound do not forget that DHT are low biased tube if they jump into A2 then the cap begin to recharge. The transformer-coupling is also problematic. The inductance acts as a choke and screw up the current transients. I mean this is all just taking but a single stage DHT is immune from all of those problems...

I would agree that some DHT has own signature that is very nice to capitalize upon, and it is possible that I would go there with my MF channel amp, or probingly return to the two stages with 6C33C. I do not know yet. Your 45 amps look interesting; I do appreciate that fact that you contrary to the most of even very experienced and knowledgeable fool present the frequency response of your amps at full power. The power at 1W shell not even be mentioned – I wish people understand it. I hate to see the Morons claim that their 20W SET run from 2Hz to 250kHz at 3W. What the holly foolishness! They need to mention that at 0.000034W their SET might run a video signal….

Anyhow, the heaters comforting with AC - is looks like you do what everyone else does. Di you try to use UHF power supply for filaments yet? Anyhow, my most interest is to get you take about one good DHT vs. the multistage DHT.  The guys in the mid of the thread did expressed their views. Still, take a the best very original WE, Klangfilm or RCA power amp (Joe Roberts, do not read further – you will have a hard attack :-) and put it next to Lamm ML2.0. The damn Lamm (with all it “horrible IDHT”) will chew and spit all those “good vintage amps”.  My post is not the tribute to 6C33C (there are tone of very bad amp with this tube) but I still am not convinced that multistage is a direction for me to go if I need to drive 110dB sensitivity in a small room and above 3200kH.

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