OTL Tube Amps-- are they superior to everything?

"Gs5556" is pretty much on the money. You have to be careful with what, and how they are mated with speakers. But, when they are matched correctly they exhibit a most voluptuous, detailed, delicate and dynamic soundstage. In short it has that "reach out and touch me" sound that is so real. Not strident or harsh at all. The bass is not as tight as the solid state kings but, the overall sound just washes away what minor weaknesses it has. They are superb sounding to say the least.

I have used the Atmasphere MA-1 with the Music "Z" transformer on both my Maggie 1.6 and 3.6 speakers. The auto-transformer is needed, actually it is a must for these speakers but, once set correctly for the impedance transformation it produced a most enjoyable sound. My favorite so far. I believe bi-amping would be the best way to go on the Maggies. Solid state on the low end and OTL on mid panel and ribbon.

I have also heard the Atmashpere at length on Sound Lab electrostatic speakers. No auto-transformer is needed here as the SLs exhibit a higher impedance. Spectacular sound here as well. Perhaps this type speaker is the best match of all for an OTL. Quality solid state amps sound very clean but just a little steril and maybe a touch less dynamic by comparison.

Check out the "OTL Online" forum. Lots of good information here. No problems with tubes on the Atmasphere. The design is mature and extremely stable. And, it is peaked in performance. You will not need to think about tweakes. The amplifier is designed as they all should be, right.

http://www.otlamp.com/forum/

I would highly recomment that you at least try an Atmasphere so that you can experience the true sound of a pure analog OTL piece of equipment. Does not matter whether you find it better, worse or indifferent. You just need to hear it when it matched up well to a speaker(with or without the auto-transformer).

There is just a gain stage then an output stage with zero feedback. Simple and truthful. No transformers or switchmode trick circuits. I personally think the magical OTL sound could be due to several different reasons. One, maybe distortion. Wegel and Lane(couple audio guru's) in 1930 published a formal paper indicating that, when a fundamental signal included its harmonics of the 2nd (@-22db); 3rd(@-26db)' 4th (@-30db), 5th (@-37db) and the 6th (@-46db) then it is characteristically pure sound. In 1960 Toshiba set out to investigate this and arrived at the same conclusions. Interestingly enough, single ended tube (SETs) and (300B) type amplifiers often display spectral contents very close to these characteristics. OTLs included.

Another reason the OTL may be preferred is due to its characteristic high output impedance. This can lead to speaker matching issues for two reasons. Depending on a given speakers crossover this will have the effect of emphasizing the frequency band around the crossover point (anywhere from 330 to 1.5Khz). Emphasizing this frequency range has the effect of producing a warmer or more robust sound. Bob Carver tries to emulate this by adding resistance in the output of his amplifiers (current output). To some extend this may work however, this will be a constant ohmic value where-as, in the OTL such as an Atmasphere this will be a dynamicly changing output-Z. There will be some interaction differences here.

A possible third reason for the highly revered bloom from an OTL amp is the fact that, since it does have a relatively high output Z(3 to 7 ohms in the Atmasphere series) this causes speakers to be less damped. And, being less damped the speaker may very well become closer to being critically damped, which is generally the most desired condition for a particular driver. Generally, when one reads the response of a speaker driver the manufacturer usually specifies it when "critically damped". However, once installed in a cabinet or frame with associated crossover components we don't know the status of driver damping or the designer's intent with a particular system. So sometimes an amplifier with a higher Z-out will improve the overall percieved performance by more closly providing critical damping to the drivers and, of course it may not be advantagous due to the particular design. Hence speaker matching is imortant. Reportedly electrostatic speakers benefit from the highish output impedance due to damping effects where-as planar speakers such as Magnepans need a very low output Z to properly damp their panels. For the latter the auto-transformer will be needed to effect the low Z-out. And, being an auto-transformer there is not much loss in this device to worry about. It is not hindered by the same issues (leakage inductance, output-Z limitations, interwinding capacitance, etc. that affects push pull transformers. Any audible masking of effects are basically insignificant once the proper ratio is selected.

I hope I did not bore you here. Again I recommend that you try an OTL as, for whatever reason, it sure produces a voluptuously immediate soundstage that reeks of musicality and just might nail you.