Some ruminations on tube amplifiers . . .
1) In my opinion Kedar recently has experienced something of an epiphany regarding OTL amplifiers. (I am sure Kedar will have some comment critical of my summary description here, and of the order in which I suggest his observations have occurred and his thinking has evolved, and he is more than welcome to comment to correct, elaborate or refine.) The common denominator connecting his enjoyment of the Tenor OTL 75w and the Berning 211/845 and the Berning Quadrature Z is the absence of an output transformer. (Yes, I know we do not like components in a vacuum; we like them in a system context with proper matching of amp to speaker, and pre-amp to amp, etc., but I am generalizing here for convenience.)
Kedar wrote recently:
The Berning Quads belong to the Spectral/Boulder sound of clean, transparent, very fast amps, with a high degree of linearity and extension, but with more valve harmonics yet not the muddiness of valves. The Bernings were doing more resolution on chorals, on Mendelssohn’s Elijah (complex tutti), and Scheherazade, and the timbre on Bruch’s violin was better due to the higher end extension. The Vitus was doing a more cohesive full bodied tone that especially favored piano and the chest during the vocals. While, unlike valves, Vitus was not rolling off the violin…I would say that the Berning was extending it more.
Kedar originally enjoyed NAT amps and KR amps and Luxman and others. He also respects Spectral and Boulder for their transparent, extended, "clean," uncolored and non-adulterating sound. He very much likes Vitus, and he thinks that Vitus could be the amplifier which pushes me over to the solid-state side of the tube to solid-state border.
Putting solid-state amps aside, I interpret Kedar's recent auditions of OTL amps to cause him to re-visit his understandings of non-OTL amps he likes. I believe his recent thinking after experiencing OTLs suggests that he now finds VTL and c-j to be a bit colored and thick in the upper bass/lower midrange and not as transparent as first thought, and that he now finds even the NATs and KRs to be less transparent and neutral than originally thought -- now that OTLs represent his new benchmark in tube transparency and neutrality.
2) Mike L reported on the Berning 211/845 thread significant experience with Atma-Sphere amps. Mike L wrote:
i still like any Atma-Sphere amplifier......they do nothing wrong and are solid great sounding amps, and the Tenor's had their design issues. but in direct comparison the Atma-Sphere was relatively dry sounding and lacked the unique 'sparkle' and fire and involvement of the mid-range of the Tenor (the Tenor's were never colored or dark, just sweet and alive). OTOH the MA2's and their more current versions are much more flexible with various speakers.
3) I like and could happily live with many different SET and push-pull tube amps. To me modern tube amps are just different flavors of wonderful. I am not put off by a little extra warmth or "color" or "thickness" in the midrange or upper bass. I am just not inclined to be critical if the sound is on the warm side of the line.
However, I am extremely critical if I hear any brightness or edginess or artificial sibilance or any mechanical type of sound or "dryness."
4) So is the midrange "beauty" and warmth of an SET just pleasant-sounding even-order harmonic distortion, which an OTL is able to avoid? Or if an audiophile wants that "musical" midrange offered by SETs how much transparency is that audiophile giving up versus an OTL in order to retain that desired SET midrange?
5) For myself, I want the midrange beauty offered by SETs over the slightly less musical midrange offered by push-pull designs. But I want higher power than SETs can offer. So I consider the NAT Magma New SE (170 watt SET).
But how much transparency am I giving up by using an output transformer? But then Ralph's designs, while Class A, are, push-pull designs. So am I forfeiting some of the SET midrange magic on that design decision? But am I making up for it with the headroom offered by 220 watts from the MA-2?
Only by comparing the MA-2 to the NAT Magma New SE will I know whether to compromise on the transparency of the OTL to capture the SET midrange magic, or whether to compromise on the SET midrange magic to achieve the greatest transparency and "you are there" effect of the OTL.
