set vs otl, which is the most musical

Set and otl amps are almost opposites in terms of many aspects of circuit design. Which of the two designs is the most musical (define musical in your own terms as there is likely not to be a universal definition acceptable to all). Which do you prefer and why?
Staying away from all the inevitable rehashes of the pitfalls of these two designs and, instead, simply focusing on the question at hand, I think the majority of listeners who have experienced the unique charms of a superior OTL and SET contender would conclude that the SET is slightly more in the camp of the beautiful/emotionally involving while the OTL leans more to the unvarnished truth/invisible conduit persuasion. Both are very compelling in their own ways. Ultimately, I opted for the truth. Continued exposure to the truth has lead me to the portal of musical beauty.
I agree with Acresverde. (I started to explain but determined that I can't say it better than Acres.)

I've owned only one pair of SETs, Antique Sound Lab Explorer 805s, that drove 86dB-(in)sensitive Quad 989s. As I don't listen at high levels, they and I matched very well until I tired of the 989s' treble balance and changed speakers.

But with a single output trode per channel, power output of an SET is always an issue unless one has very sensitive speakers. Mine are the opposite (at 84dB sensitivity), so I've opted for all trodes but lots of them, in the form of ASL Hurricanes in triode.

If I win the lottery, I'll buy a pair of 140-Watt Atma-Sphere MA-1s and keep one pair or the other. I love my ASL 'Canes, but maybe those OTLs will sound a little quicker, cleaner, bigger, etc.
Nice as SET's are, they are always a bit different, specially in the high frequency Area... I own OTL's from Atma-Sphere, and in my opinion, that's the Real Thing (or very close to it). They combine the best from all worlds, Body, a High Frequency Range to die for and a holographic speed which has to be heard to believe.
But, you need a matching speaker to get the best out of it ( 8 ohms+).
there is no way to generalize. set amps may be very linear in their performance or sound like a vintage tube amp of the 70's. otl amps may also have the characteristics of accuracy or "romance" . it is necessary to evaluate each amp on its own merites, regardless of its design.

generalizations are usually wrong, most of the time.
>>generalizations are usually wrong, most of the time<<

Maybe and that's for certain.
I have owned both SETs and OTLs and, for me, the realism and speed of the OTL (Atmasphere MA 2.2) reigns. Never heard better.
I wonder how you would characterize a SET OTL :)
I completely disagree

I have Lamm ML 2.1's at 18 wpc driving my behemoth Wilson X-2 Alexandria speakers. I have owned literally every high end amp available and I can say that I will never buy another amp. These are as good as it gets.Bear in mind as well that it all depends on the sensitivity of ones speakers. Mine are rated at 95 Db.
when all is right....less is more. in other words; when the speaker is properly matched to the OTL amp then to my ears an OTL is the closer to my ideal than SET's. i've had big OTL's (Atma MA2 for a few weeks) and more modestly powered OTL's (Tenor 75W for three years). an OTL seems to have overall more clarity and imposes less of a signature of it's own. there is more bass articulation and deeper extention 'generally' with an OTL and very extended highs.

as mentioned above an OTL can sound 'tubey' and an SET can be fairly neutral and extended.

my answer is that an OTL is more musical if one's definition of 'musical' is 'reality'.......if your definition of 'musical' is 'rounder' and more 'lush'.....then your answer might be SET. there is no wrong choice.

my perfect amp is a combination of the best parts of the Tenor OTL performance added to the strengths of solid state (darTZeel.....or Tenor Hybrid).

oneobgyn: have you ever owned a conrad johnson mv 125 ?

i prefer it to any lamm equipment.

i have heard lamm pre amps and amps many times. yes they are fine components, but not the best.

have you heard a david berning sigfried ?

the point: there is no best anything. it's a matter of taste.
I would agree with Thomasheisig with regard to the Atmas. I once heard these amps with the top of the line full range Sound Lab Electrostats and almost fell off my chair. The sound was nothing short of breathtaking. The problem I have with SET amps is there output capabilities and distortion products. Ten percent distortion can't be taken seriously as an audiophile product as it's a profound sonic coloration. I know that sounds rather brutal but its just my opinion. Even though a piece of gear has its own inherent sound, I would preffer something that creates less coloration and a bit more neutrality. I don't want everything to sound pretty. G. Garfield
"the point: there is no best anything. it's a matter of taste."

I completely agree.

Yes, I have owned CJ. Not my cup of tea at all.

I will still take SET any day over OTL.

BTW, I don't like the LAMM Reference preamp. I had it and gave it the boot. Presently have the ARC Ref 3 which is magnificent but then that is my taste. The Lamm ML 2.1 with the Ref 3 is for me as good as it gets.
Excuse me for derailing the thread, but could someone answer with a simple yes or the OTL's and their little tube armies run especially hot? Thanks for the response.
atma-sphere's used to have fans in them for cooling. They do run hot but i could name a few non otl amps that ran hot too. With otl amps its more a function of what type of output tube there using and how their biasing the tube. Generally speaking u wont find otl amps using 6550 or 6CA7's as this would be an impedence mismatch. G. Garfield
Boa2, yes, OTL's typically run quite hot. the three OTL brands i am familiar with (Atmasphere, Tenor and Joule) all run pretty hot.....the big Atmasphere and big Joule's run the hottest in my the degree that summertime listening in certain parts of the country is avoided if you don't have air conditioning.

Before I got my M60s, my biggest concern was the dreaded heatwave they were purported to throw off. I live just north of what's left of New Orleans where it's typically in the mid 90s both temperature and humidity wise for 6 months of the year. Well, the bad news is that they are mighty toasty but the good news is that somehow it goes completely unnoticed in my no-so-gigantic listening room, come summer or winter. The thermal load just seems to dissipate without leaving a mark. Makes no sense to me but that's the bottom line. I do listen about 11' away from the amps, though. YMMV
Boa2, in response to your question, amps designed for Class A operation all run hot, whether OTL or not, whether tube or solid state. It's the Class A operation, not the fact that they are OTLs, that results in the heat. The best of the OTL amps (Atma-Sphere, Joule, Tenor) are run in Class A for best sound. For a while, Atma-Sphere made the MA-1 and MA-2 models with an optional switch to change operation from Class A to Class A/B to address the heat issue, but I think Ralph dropped that as a standard feature because most owners never wanted to make the sonic trade-off and left the amps set for Class A anyway.

[D]o the OTL's and their little tube armies run especially hot?
I am not a techie, but I think that Howard has put his finger on one of the heat issues. I could be wrong, since I have no personal understanding of circuit design, but I think that large number of output tubes needed for an OTL design, along with the Class A operation, contributes to the heat load. And then all of those driver and input tubes. My Atma M60s each have 12 tubes (so thats 24 for stereo) and my Joule VZN-80 has 16 tubes total (including 8 of those Russian monsters). Put it all together and the heat is an issue, but one I have chosen to live with.
Thanks everyone for the info. We've previously had amps that heated the entire upstairs of our apartment, as well as running up the electricity bill. I think if we had more space, and a quieter AC system, I'd jump at the chance to hear the OTL's. The only one I've heard represents merely a toe dip into the pool of OTL's. Jax2 came through last year with his Berning MicroZOTL, and we ran it through our Klipschorns. Understandably, it's 1 watt didn't lend much weight to the music, but oh my did the vocals sound delicious.
The Moscode 401HR is OTL. Runs reasonably cool...
My Trios sounded not so good with an Atma-sphere M60. I think there is some impedence dips in the highs. The highs were rolled off. My Viva Auroras 845 are a perfect match. With my Silverline Sinfonias the M60 were very good. They are a flat 8 ohms. I still liked the Vivas better though. Way more goose bumps. I didn't find in my comparisons The M60 gives much of that. This is just my findings with my equipment. Others I'm sure might find different. OTLs do definatley need flat impedance. 8ohms or higher.
TVAD & others, bear with me on this one as I'm not as technically informed - I thought all OTL's used tubes in their output stage? The Moscode 401HR is a hybrid. Are the MOSFET's then somehow run without an output transformer? (I'm not sure I understand the design, but have heard and read nothing but big positives about the Moscode, so it must be doing something right!)

Can anyone clarify this a bit? Thanks.
Denf, here's the explanation on the Moscode Website. You'll need to scroll down to get to the MOSFET output section.

I'm not a techie nor an engineer.
I'd like to comment on something said back on July 3rd:

"Ten percent distortion can't be taken seriously as an audiophile product as it's a profound sonic coloration."

Well you would think so, but that's not necessarily the case. A recent pair of Audio Engineering Society papers presented by Earl Geddes and Lidia Lee showed what essentially amounts to a NEGATIVE correlation between harmonic distortion percentage and listener preference!

Thirty percent second harmonic distortion was found to be statistically undetectable, while very low percentages of high order harmonic distortion such as is generated by global negative feedback in an amplifier were both audible and objectionable. In addition, "crossover distortion" such as is typically produced by amplifiers operating in Class B mode was found to be particularly audible and objectionable. For years amplifier designers have been getting rid of large percentages of low order distortion and replacing it with small percentages of high order distortion, and evidently this is often a step in the wrong direction sonically.

If that ten percent distortion is second order harmonics, it is probably inaudible or barely audible, and is very unlikely to be perceived as an objectionable coloration.

I don't mean to be picking on you, Webmaster. I'd have said the exact same thing (and probably have many times) had I not been fairly close to the study and taken the listening test myself. My scores were not included in the data used because I knew something about the focus of the trials, so I was not a totally blind participant.

The papers were presented about two years ago, and are only available through the Audio Engineering Society.

Getting back to the question at hand, I'd say that with appropriate speaker/amplifier matching both approaches can sound very, very, very good.

Another very important point is that any SET is only producing 10% 2nd-order HD at its max output or very close to it. For this reason, I do think it's a good idea to plan a system with the SETs not required to go about 50% or so output. At that level, you're normally talking about a few percent THD, 90% 2nd harmonic, proven in testing to be entirely inaudible.

One study showed 7th order HD to be around 20x more objectionable than 2nd order.
Thanks for your insightful responses, Audiokinesis and Paulofbrecht. What you said was certainly pretty shocking to me! I did some googling to try to find those papers you were talking about by Geddes and Lee, but I have not been able to come up with anything. Would you happen to have some useful links?
Amfibius, the papers by Geddes and Lee I mentioned were presented at the 115th convention of the Audio Engineering Society, in October 2003. You can order them from the Society. They are entitled "Auditory Perception of Nonlinear Distortion - Theory" and "Auditory Perception of Nonlinear Distortion", and can be ordered as Preprint Number 5890 and Preprint Number 5891.

If you are an Audio Engineerng Society member, you can read them online or print them out.