Maybe, I can help jump start your post by providing a mediocre technical response. I think the purists may say, that the single SET tube option sounds best, because the entire signal going in, is the same signal coming out. So, the signal path is not being split apart and then reassembled. That's all I can offer, good or bad, as I've been exploring my own SET amp options and have been wondering the same thing.
One example of production, would be Border Patrol's S10 (SET) and S20 (PSET) 300B amp options. The S20 is for driving less efficient speakers, but the starting costs of both amps are the same. I may be wrong, but if your speakers don't require the extra power, why not go for the simpler circuit?
I'm not sure, but the extra power of some PSET designs may provide greater authority, so better overall control and balance across the frequencies, while the single SET solution gives you the best midrange. It may be that the choices come down to how the sound is presented to you, so not really a "better" answer.
Hopefully, someone will chime in and help clear up any BS I may have added..
This is an often discussed point for those in the SET world.Some will say the problem with PSET is getting both tubes to work in an identical manner. They say one tube does more than the other (they don't stay in a equal balanced harmony). Others strongly dispute this claim and say "proper" design and execution overcomes this problem. I tend to lean toward the latter camp and believe good implementation is the key for successful PSET amplfiers. I use a single tube(SET) but I don't need the additional power PSET provides. If added power isn't required, a single output tube is nice and simple.
To me, the issue may even be a bit more complicated. While I agree with Charles that proper implementation may help to overcome the theoretical disadvantages of PSET, it is likely to be more expensive. As a result, if one does not need increased power, then SET makes the most send. However, if one DOES need increased power, then the other comparison is PSET using lower power tubes (300b, 2a3, 45) versus SET using higher power tubes (845, 211, EL34).
"the signal path being split apart and then reassembled" is a description of how a push-pull amp works.
PSET amp does not split the signal, the driver tube simply drives the two output tubes via a capacitor or interstage transformer and those two tubes output are combined into the output transformer.
You are right, Kenny describes what happens to the signal (phase splitting) with a push pull circuit I believe. The stated advantage of SET/PSET is the absence of signal splitting.
Yes, no phase splitting, but as Charles1dad mentioned, there is the issue of one tube ending up doing most of the work. I know of an amp builder/designer who mentioned how hard it was for him to get PSETs to work because of this problem. But, he did hear the PSET amp I own (Audionote Kageki) in my system and agreed that it sounded very good.
The purists don't like PSET because they believe that the more tubes that as you pass the signal through more tubes, even in parallel, the sound becomes muddier. This is the same objection raised with high power pushpull amps that have multiple output tubes.
On the plus side, at least theoretically, the output impedance of the tubes operating in parallel is halved, meaning that the either the amp output impedance will also be lower or the designer can use a smaller turn ratio in the output tube (generally considered desirable).
Theory aside, I have heard plenty of good SETs, PSETs, pushpull and OTL amps so I have don't really care about the design approach taken.
Thank you all for the replies .
"I have heard plenty of good SETs, PSETs, pushpull and OTL amps so I have don't really care about the design approach taken."
Could you give me a list please , especially the PSETs ?
PM me if you wish .
Some well regarded examples of PSET,
AN UK and AN Kits,
These cover a broad price range spectrum.
I knew I could count on you guys! Thanks, Kenny
The PSETs I have heard included the Audionote Kageki (the one I own), Audionote Gaku-On and Sogon. I have also heard two custom-built amps, one a 300B amp the other a 45 amp. All of them sounded really good.
I have heard quite a few SET amps, e.g., Audion, Wavelength, Art Audio and a lot of custom/home built amps. I particularly liked the 211 amp built by Wyetech and a 845 (I believe) by Viva.
I own two pushpull amps that I like very much. One is a custom amp that uses two 45 tubes per channel. The amp that I currently run in my system (the Kageki is on loan to a friend) is a cutom rebuild of a Western Electric 133 amp. This amp uses 348 driver tubes and 349 output tubes (a whopping 5 watts/channel). As compared to the Kageki, the 133 has tighter, punchier bass, and an even more beautiful midrange. The tradeoff is that, like most pushpull amps, that tighter and "punchier" bass sounds a little mechanical and has a sameness no matter what is being played, while the Kageki is more varied and "tuneful" in its bass presentation. The Kageki is also a bit more open and extended sounding it the top end. Like everything else in audio, tradeoffs are involved. A local dealer owns a Western Electric 59A amp (252a tube) that sounds REALLY good, but that amp carries a CRAZY price. This is the best pushpull amp I've heard.
The commercial OTLs I have heard, and like, include models from Atmashphere, Joule and S.A.P. The Atmasphere has, in comparison to the Joule and S.A.P., a leaner sound. Which would work best, is a matter of taste and system matching. All of these amps deliver a very immediate, lively sound that I find VERY appealing (some high power pushpulls deliver some of that kind of punch, but almost always with an unpleasantly hard and artificially edgy quality). The very best OTLs I've heard were built by a Greek hobbyist (he made somewhere around ten amps). The two version I heard were unbelievably dynamic, yet smooth and utterly musical--up there with the 59A as best amps I've heard.
Jet and Charles,
I wanted to thank you for clearing up my split path comment, as I do have a push-pull amp and will be going SET. It sounds like with PSET the goal is to get both tubes of the parallel circuit to work exactly the same, because they are carrying the same signal. So, the increased power comes from the doubling of the same signal. Does that sound about right?
You achieve double the power because you doubled the # of output tubes used. I believe a SET would be a fine match with your Hornings. Your speaker deserves a high quality SET that has premium quality output trandformers and very stout power supply built.Good luck.
Generally speaking, the PSET approach will get you more power, but, not the same amount of power that one would get by using the same kind of tube in a pushpull configuration.
Also, how much more power you would get with two output tubes vs. one is somewhat unclear. As Charles1dad has mentioned, there is the issue of the tubes not working identically. With my Audionote Kageki amps, I have noticed that after more than a year of operation, the two output tubes per channel will test quite differently, particularly for transconductance, when I test them on my Amplitrex tester. Whether this IS the result of the kind of imbalance issues that are claimed for PSET designs, or is attributable to something else, I have noticed this "problem." The amp will still sound great even when the tubes test very differently, but, with one tube being much weaker than the other output must be lower than before the tube started getting weak. I don't need much power, so that might account for why the amps still sound quite good. That the tubes in both amps would test so differently initially bothered me a bit, but, I "solved" that problem by no longer testing the tubes.
Thank you for the list and compare...very helpful .
"but, I "solved" that problem by no longer testing the tubes."
Love it !
I have always felt that 'if it ain't broke , don't fix it !
And thanks to Charles 1 dad also .
I will check out these suggestions and see what the availability and price looks like .
As I feared these things are out of my price range !
About the only thing that I could maybe afford would be a used Audion and the availability is not good .
Thank you to all who replied here . At least I learned something and that is always a good thing .
Happy Tunes .
The PSET amplifiers do seem to cost quite a bit more than pure SET versions. Of course this means a higher efficiency speaker is required for the lower power SET but that's a choice worth considering IMO.
Oh I whole heartily agree Charles .
Some time ago I started a thread seeking suggestions for high efficiency speakers approximating the sound of my De Capo i's and all of the suggestions were in the price range of these PSET's .
Champagne desires and a beer budget !