if the increased ratio of second and/or third order harmonics in tube equipment masks the higher order harmonics, are you also saying that the frequency response of tube amps in the highest audible frequencies is NOT lower than that of SS amps, but we just don’t "hear" those higher frequencies because they are masked by the 2d/3d orders?
Yes.
Because that means nothing at all comparing tubes/versus S.S. in general...
My post was not meant to address tubes/transistors, it was meant to address how distortion interacts with our ears. What I did not mention in that post is that if you can apply enough feedback to a solid state amp it will sound very natural and the typical brightness and harshness on top will be gone. But that is a tricky thing to do because of something called ’phase margin’ in audio circuits. Essentially there are frequency poles which cause phase shift. At some high frequency, these poles cause enough phase shift that feedback becomes positive rather than negative and the amp will oscillate. This is why for many decades amps have not had enough feedback; with insufficient feedback the circuit will be brighter and harsher than real life. Hence the ’solid state’ sound of the last 50 years.
By the way the human hearing faculties are way less more deceptive that "skeptic sunday scientist" says they are... Reason is simple, evolution.... recognizing timbre voice speech and the source of sounds is vital tool for survival.... The first sense to be born is hearing, the baby listen his mother voice, and in coma and death you can speak with people, it is the last sense organ to go....
If you want to talk about evolution, the ear is the most sensitive at birdsong frequencies as the birds are the first warning that a predator is in the area. This is the Fletcher-Munson curve.
The sound was pleasant but not $100k worth to me. Euphonic as all hell. Detail I know is there was gone, replaced with a warm blanket of sound. So is the loss of detail and an abundance of warmth a result of frequency response or an excess of 2nd harmonic distortion?
This sure sounds to me like an amplifier with too little feedback. Distortion of all types will reduce detail. You know you are making progress when you experience smoothness and more detail at the same time. The smoothness is a lack of higher ordered harmonic distortion and IMD; the detail comes from that lack of distortion.
Amps that exhibit a 2nd order as their primary distortion component have what is mathematically a ’quadratic non-linearity’. A good example of this is an SET where the 2nd harmonic dominates. But the higher orders do not fall off all that quickly; it is only the 2nd (and the 3rd which appears at a lower level) that mask the presence of these higher orders. Because the distortion is so profound, quite simply there is detail lost while sounding otherwise quite smooth.
For instance, I love the Conrad Johnson Premiere 12. They are the ne plus ultra of amplifiers in my mind. Neutral? Hardly! But I can’t really explain why. Those are just very colorful seductive amps.
I was wondering about distortion specifically.
When you combine single-ended and push-pull you have two non-linearities- quadratic and cubic. The Cubic expresses the 3rd as its dominant harmonic component. Due to algebraic summing, this type of circuit typically also exhibits a bit more prominent 5th harmonic. But it will have a lot of the 2nd as well. Distortion does not fall off all that quickly as the order of the harmonic is increased. This is the traditional ’tube sound’ coming out of the golden age of hifi with such amps as the Citation 2 or Dynaco ST-70. Feedback is used to control distortion and to a limited extent reduce the output impedance, but 12-15dB is typical as much more than that risks oscillation. So you get a rich sound (not as rich as SETs) and that 5th sort of acts like a touch of detail.
IMO/IME if you want to use a tube amplifier, getting away from that 2nd harmonic will really allow the amp to be far more neutral and transparent. The only way to do this I know of is to run the amp fully differential from input to output, so that it mostly expresses a 3rd harmonic as the dominant. **This is a good practice for solid state too** and for exactly the same reason! The 3rd is treated the same by the ear as the 2nd but in such circuits often occurs about 1/10th the amplitude as the 2nd is in SETs (this is assuming open loop- no feedback). The tricky bit is that even orders are cancelled not just in the output section but in each stage so distortion isn’t compounded from stage to stage through the amp. For this reason amps with a cubic non-linearity have the succeeding harmonic orders falling off at a faster rate (hence ’cubic’). The reduced higher orders allows the circuit to be smoother and with more detail!
I have one special tube amp and class Ds, can’t seem to decide between them.
Class D amps are a special case of solid state. They can be run with zero feedback (the big trick with zero feedback examples is that RFI and EMI emissions are hard to control), a little or really quite a lot. The high feedback amps have feedback so high that they actually are designed to exceed their own phase margins and go into oscillation! This type of class D amp is known as ’self oscillating’; the oscillation is used as the switching frequency. They have the advantage of being able to use prodigious amounts of feedback in excess of 35dB because they are already oscillating. This allows them to clean up the distortion caused by the feedback itself (which tends to be higher ordered harmonics and is why amps with insufficient feedback have a brightness to them that isn’t natural). So such amps can sound very smooth, much like a really good tube amp.
