what is your opinion ?

I honestly not that sure what are you trying to achieve ?

I participate on this and other forums simply because I enjoy music and I enjoy helping out where I can. I like to simply state the facts; I apologize if this has put you off.

' in one of my post mentioned D.Berning OTL design you have instantly made a comment he uses this, that , semiconducters etc, etc, as a matter of you start to critise other OTL Design

I think you will find that the above statement is incorrect! I was not critical of the Berning amp. I merely made a comment to clarify point of fact. Here is my comment:

FWIW the Berning amplifier is **brilliant**, but not an OTL as it has both semiconductors and an output transformer in its output section.

Note the use of the word 'brilliant' (emphasis added in the above quote). This means I have a lot of respect for the design (which Berning patented) and a lot of respect for the man himself. Nor was I critical of other OTL designs. I have the feeling you are trying to put words in my mouth! You'll also note that when I got into this conversation I did not mention what OTL I was playing in my system.


regarding zipost's comments, obviously there is a lot of tongue in cheek going on there :)  Its pretty funny and obviously meant to be exactly that.
Regarding this comment

all of sudden got bombarded by OTL Amps lectured Incapabilities of VOTT And apogee ribbons

-I feel you misinterpreted my comments about both speakers entirely. I was trying to get you to understand what the strengths of both were, plus what you can do to improve the Altecs further since that is what you are using; I ran VOTTs for many years.

Mine is better Yours is worst kind of aproach I Personally believe is absurd

You'll notice I stay away from that sort of talk.

I fully respect what you are saying but initial invention of OTL amp as far as I know creation of J.Futtermam, it means the wheel already has been invented ! talented guys like yourselfs improve /re create OTL Amp Design Such as Berning makes Delicious OTL Amps Acuhorn makes OTL Amps and many more, but I sincerely do not understand why we are discussing OTL Amps, my initial question was SET Amps and Horns and really wanted to hear from SET Amps and horn lovers or enthusiasts . kindest regards.Sabih

Actually the first OTL patents in the US preceded Futterman's patent. He did not invent the technology, he developed a means of positive feedback to help the drive of the top tube in the output section to be driven as well as the bottom one.


We got around the problem entirely by a different circuit. I got the idea during a dream back in 1976. At the time I had no idea who Futterman was.  FWIW the Berning amplifier is brilliant, but not an OTL as it has both semiconductors and an output transformer in its output section.


My last two posts here (including this one) are corrections to set the record straight. FWIW your opening post does not suggest that this thread is about SETs; it simply asks about 'old school designs' and whether we are re-inventing the wheel (the answer to the latter question is rather obviously 'no.').

as far I know everything copy of copy nothing is original even in terms of Audio engineering J.Futterman came up Design of with OTL amps rather talented E.engineers improve or re create their own design

@sabih  Just FWIW, the OTL we make is not a Futterman circuit. Its entirely our own unique design for which we were awarded a patent many years ago. Also FWIW, the means of operation is actually two SET amps wired in a unique bridge configuration called a 'Circlotron'.

Maybe Ralph may want to comment on how the 3C24 would match with your Altecs.

I think it might work rather well but the design of the output transformer would be paramount, as this tube likes to run at some pretty high voltages! This requires a higher turns ratio on the transformer as well as some other considerations for high voltage operation. How much power does it make- about 20 watts or so?

I run horn speakers and I've run SETs on them many times. But I prefer an OTL on them as it has obviously wider bandwidth, lower distortion, greater detail, etc. No going back.

Altecs have controlled directivity in the mids and highs. Your panel speakers need to use the wall behind them to work properly- that needs to be about 5 feet minimum and you can’t have side walls too close or the reflections will mess with the soundstage and make things sound harsher.

The Altecs are likely 16 ohms- all amps make less distortion into higher impedances, and your tube amps tend to make lower ordered harmonic distortion, which is far less audible to the ear than the higher ordered harmonics that are typical of most solid state amps. Plus they are efficient enough to properly take advantage of the very lower power of your SETs. This all works in your favor. In order to get the most out of SETs, they should not be driven past about 20% of their total power, as those higher ordered harmonics start to show up, making them sound loud. A good stereo won’t sound loud even when it is!

There are ways to improve what you are hearing even further. In the Altecs the horn tends to resonate due to its construction; if you can damp it with some proper extensional damping materials it will get smoother. But the horn itself has issues since it was designed (and fairly well for the time) before computer optimization. Modern horns can be smoother and more detailed as a result.


Believe it or not there are also modern tube amps that are more revealing than the SETs on Altecs. The technology has advanced...


BTW the solid state amps you were playing very likely had insufficient Gain Bandwidth Product to really allow them to be musical. Gain Bandwidth Product is a tricky bit to explain, but in a nutshell it means that while you might have adequate feedback to control distortion at low frequencies, you don’t at high frequencies, which causes the latter to be harsher. This has been a problem with all amplifiers over the last 50 years, including tubes, but because tube amps tend to make lower ordered harmonics they tend to sound smoother. This has fueled the tubes vs transistor debate for the last 50-60 years! But its really not about tubes, its about getting enough gain bandwidth product to really allow you to run enough feedback, and that is a real trick- its really only become practically possible fairly recently.