Why has no-one brought up the assertations of Cheever's MIT thesis mentioned early in this thread?? Cheever claims/proves(?) that non-negative feedback (open loop) single-ended designs, either tubed or SS, are superior in TONAL QUALITY both objectively and subjectively.
Linear triodes create pleasing LOW-ORDER (2nd, 3rd, etc) distortion, while most SS designs are plagued with nasty-sounding HIGH-ORDER (5th, 6th, and up) distortion. The physiology of our ears is such that our ears actually create 2nd and 3rd harmonic distortion OF THEIR OWN in the cochlea canal. This effect serves to "cancel out" triode distortion preserving harmonic integrity. Interestingly, our ears also cancel out higher order distortion that follows a PARTICULAR PATTERN. However, most SS designs do not follow that pattern. SS may have incredibly low THD figures, but the negative feedback required to do that is what screws up the harmonic portrayal. Cheever asserts that EVEN AS LITTLE AS 3dB OF FEEDBACK will screw up the sound.
SS designs with ZERO feedback and the correct PATTERN of rising order distortion may IN THEORY sound as good as well-implemented single-ended tube designs. I'd encourage everyone to study the thesis for themselves, and post your thoughts accordingly.
Linear triodes create pleasing LOW-ORDER (2nd, 3rd, etc) distortion, while most SS designs are plagued with nasty-sounding HIGH-ORDER (5th, 6th, and up) distortion. The physiology of our ears is such that our ears actually create 2nd and 3rd harmonic distortion OF THEIR OWN in the cochlea canal. This effect serves to "cancel out" triode distortion preserving harmonic integrity. Interestingly, our ears also cancel out higher order distortion that follows a PARTICULAR PATTERN. However, most SS designs do not follow that pattern. SS may have incredibly low THD figures, but the negative feedback required to do that is what screws up the harmonic portrayal. Cheever asserts that EVEN AS LITTLE AS 3dB OF FEEDBACK will screw up the sound.
SS designs with ZERO feedback and the correct PATTERN of rising order distortion may IN THEORY sound as good as well-implemented single-ended tube designs. I'd encourage everyone to study the thesis for themselves, and post your thoughts accordingly.