Hello all- I am in my 50s and have been messing enjoyably with tubes since middle school (audio, amateur radio vintage equipment, etc.)... minus a few decades in between where work, family, etc., took front priority....
... but, to date, nearly all of my experience was with push-pull circuitry, and, I always thought that single-ended might largely though not entirely be an overhyped or elitist fad- or at least not particularly worth the bother.
But then, this past Christmas, I got my son a 'TubeCube 7" S-E EL84, and we built some nice little fullrange speakers with some mid-priced Fountek drivers.... and, I was just repeatedly awestruck at the enjoyable extraordinarily lifelike detail that I heard coming out of a $150 (on sale) 3wpc amplifier and a pair of $19 each fullrange drivers. And I was surprised just how big three really nice watts could sound.
Needless to say, I no longer write off single-ended amps, and, having my attitude shattered as to S.E., I am now hankering to also see what a SE triode amp would be like.
Which has me studying up at length on various tubes and designs for single-ended triode. I'm leaning towards some of the dual triode 'pass regulator' tubes
What I would like to know is what sort of approximate lifespan one could hope for out of tubes like 6AS7/ 6080 family/ 6336, given that single-ended means Class A which means drawing full dissipation and full cathode emission 100% of the operating time. I am in a "go big or go home" mood to build something moderately outlandish, and really drawn to the 6336, but if even some of these bigger tubes have finite lifespan in this operating mode, then I might more sensibly stick to more widely and economically available tubes like the 6AS7 and its Soviet and Chinese cousins.
Thanks in advance for sharing your insights and experiences.
... but, to date, nearly all of my experience was with push-pull circuitry, and, I always thought that single-ended might largely though not entirely be an overhyped or elitist fad- or at least not particularly worth the bother.
But then, this past Christmas, I got my son a 'TubeCube 7" S-E EL84, and we built some nice little fullrange speakers with some mid-priced Fountek drivers.... and, I was just repeatedly awestruck at the enjoyable extraordinarily lifelike detail that I heard coming out of a $150 (on sale) 3wpc amplifier and a pair of $19 each fullrange drivers. And I was surprised just how big three really nice watts could sound.
Needless to say, I no longer write off single-ended amps, and, having my attitude shattered as to S.E., I am now hankering to also see what a SE triode amp would be like.
Which has me studying up at length on various tubes and designs for single-ended triode. I'm leaning towards some of the dual triode 'pass regulator' tubes
What I would like to know is what sort of approximate lifespan one could hope for out of tubes like 6AS7/ 6080 family/ 6336, given that single-ended means Class A which means drawing full dissipation and full cathode emission 100% of the operating time. I am in a "go big or go home" mood to build something moderately outlandish, and really drawn to the 6336, but if even some of these bigger tubes have finite lifespan in this operating mode, then I might more sensibly stick to more widely and economically available tubes like the 6AS7 and its Soviet and Chinese cousins.
Thanks in advance for sharing your insights and experiences.
I have bought and built both SE and PP amplifiers. According to my experience, on SE amplifiers the output transformer cost is significantly higher than PP at a given quality level. I will therefore start the search by checking what kind of output transformer I could get with the available budget, and then select the output tube. Good NOS 6AS7/6080 tubes are cheap so I would not worry about the lifespan. I have a box full of them, but I haven't built anything yet because the required transformer would be a oddball one that need to be custom wound/ordered at price premium, and you will still get only about 8W of clean power from a 6AS7 in single ended mode with both section in parallel. The exact same (somewhat pricey) output transformer could be driven by equally cheap and easily available sweep tubes such as 6KG6/EL509 in screen drive mode and the output power may well be over 10W, but I haven't tried any enhanced triode/screen driven amp yet, so I cannot comment on the sonic quality.
By the way I also have a TubeCube 7. This amplifier is sold with different names and the most common one is PA0901A, you will find a few thread on this forum with this search string. On this thread: APPJ EL84 SE mini Tube Amp, PA0901A at post #62 I described my modifications. I can attest that it sounds good, within the limits of the very tiny output transformers (400 grams each). The manufacturer spared on safety and reliability to meet the attractive price point while keeping a shiny look. This is common on current China production.
By the way I also have a TubeCube 7. This amplifier is sold with different names and the most common one is PA0901A, you will find a few thread on this forum with this search string. On this thread: APPJ EL84 SE mini Tube Amp, PA0901A at post #62 I described my modifications. I can attest that it sounds good, within the limits of the very tiny output transformers (400 grams each). The manufacturer spared on safety and reliability to meet the attractive price point while keeping a shiny look. This is common on current China production.
First: I haven't used a regulator tube as an amplifier (yet) so can't comment on their sonic qualities.
Personally I'm very fond of TV sweep tubes.
Much higher current capabilities than the typical audio types, very reliable when operated within their specs and many of them (still) cheap.
Many possible ways to use them: pentode, triode, UL, screen drive, 'crazy drive' (G1 + G2)...
With triode and UL you have to be careful as they have usually a low G2 voltage rating due to their high sensitivity on G2.
Tubelab George has a nice page on the 6AV5 on his site, using it as a SET.
Personally I'm very fond of TV sweep tubes.
Much higher current capabilities than the typical audio types, very reliable when operated within their specs and many of them (still) cheap.
Many possible ways to use them: pentode, triode, UL, screen drive, 'crazy drive' (G1 + G2)...
With triode and UL you have to be careful as they have usually a low G2 voltage rating due to their high sensitivity on G2.
Tubelab George has a nice page on the 6AV5 on his site, using it as a SET.
First thing to reconsider is the assumption of needing 100% dissipation. There is no reason you can't back the bias off to 70% - 80% of your plate power max with Class A operation. If you don't run your amp normally at full volume signal to the outputs you don't utilize the full capability of the 100% idle current setting, anyway.
Great point, thank you- and since from what I am reading, these regulator-type triodes often have less than well matched 'halves' I definitely think that I am going to include easily accessible adjustable bias (making part of the cathode resistor fixed, and part wirewound potentiometer) to be able to easily adjust bias on individual tubes _and_ tube halves- and, that way, I can also dial back the dissipation for situations in which I am not calling for full throttle (and less than full throttle will be normal) Thanks
I turned 70 last july and just finished my first Set build, more enjoyment building it than I could ever have imagined, now I'm addicted and want to build more projects, possible a tube preamp. I have about 40 or so hours on my build and absolutely love it! I haven't looked at it on a scope yet, maybe this week end but it sounds wonderful, is clean and super quiet. Mine is the KT88 build Mark from Blueglow has up on YouTube, great teacher and inspired me to give it a try.
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