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I'm a bit confused as to what you are asking The title says single-ended pentodes, but you ask about triodes...
The title question suggests to me that triodes are usually chosen when one reaches for a single ended tube amp.
. But, if SE pentodes are outnumbered, they are still not too hard to find. Quicksilver makes a single ended KT88.... am sure that I missed a few. Not to mention all of the vintage stuff, and DIY . . . Also, in the land of tube guitar amplifiers the single ended pentode is still popular. (Marshall class5, Laney Lionheart, etc.)So there you go. The SEP is still alive and kicking. It ain't going away anytime soon.
Does anyone actually run pentodes in true pentode mode anymore? I thought all pentode amps were run in ultra-linear these days due to distortion.
Like most things, implementation is often more important that topology... but I agree with cheap jack, if your goal is the best amplifier possible I think triodes are the only real choice. Whether PP or SE, that will get a lot more debate!
i agree implementation is important the almarro a205a mkll, 5wpc w/el84 tubes run sep, is an absolutely killer amp, imo. it has been favorably compared to amps 3 times its price, including set amps...doug s.
I sort of specialize in designing single ended amps in pentode mode. It has gone so far that I am not interested in designing amps with output triodes, unless it is to prove a point, or improve on current implementation of output triodes. The main reason triodes are popular is the fact that they are easier to work with, less connections and grids to use, less knowledge necessary. Knowledge has been lost to most, among other reasons because vacuum tubes are basically obsolete and are not taught at universities. Maybe the basics of triodes are easy enough to grasp, but pentodes are a different case. Not to mention the difference between the operation of small signal pentodes and output power beam tetrodes and pentodes.I have managed to design SE tube amps with pentodes and beam tetrodes which were initially defined as "the sound of triode with the power of pentode. The RH84 and RH807 are two examples. You can check out my blogRh-amps.blogspot.comfor information, and you can also search the net for all the praise and controversy those amps have underwent in the past more than a decade.RH amps have started as a challenge to triode (mostly DHT) SE amps. If you reconsider, it's a repetition of 2A3/300B, and 211/845 amps, at least in the SE field. 6V heater versions of 2A3 included, and "special quality new production versions" taken into account, of course. Not to mention the circuits, repetition of the same driver tubes in the same configuration all over again. Than there is the claim of power, where some amps are declared as operating in class A2, although they are dirct coupled at the very best, but the drivers cannot push the output tubes in class A2, thus power remains, for instance, 18W instead of the declared 30 or so Watts. Similarly but less bluntly, EL84 amps are specified as 2W in triode mode (how is that possible?), and generally some 25W anode dissipation triode strapped amps are declared with output power that can be obtained with 40W dissipation DHT's. Why bother? A 25W dissipation pentode will hive you up to 10W of output power with a good application, and sound that will not be second to DHT, but you have to be creative and know hoe to do it... and that will avoid any marketing gimmick. I guess this post will cause harsh remarks and fierce attacks. I am used to that, anyway. It's either being silent or attracting all sorts of criticism from people who would like the world to go on like they are used to, unstirred. For the purpose of this thread I guess the major problem is the fact that most are not DIY-ers while my amps are not products for sale - this limits the possibility for direct comparison with similar commercial amps mentioned above.
A lot of the tubes mentioned in this thread are actually beam tetrodes, right? Are beam tetrodes inherently lower in distortion, even when treated as pentodes in a circuit, than a true pentode?
