in fact, an amp designed by anyone to have the distortion structure that Ralph says can sound blah, OK, good, very good or great depending on the implementation of a million different factors. Ralph thinks its mainly one factor.....to each his own.
Its clear that you either didn’t read my post or didn’t understand what is says. As a result, the first statement is false. The second is too- because there is way more than one factor at play!
In order to get consisent distortion with less than 1 degree of phase shift at all frequencies in the audio passband there are basically two means to do it- either have wide enough bandwidth with no feedback or to have enough gain bandwidth product that it can support the feedback, especially at 10KHz and above.
That’s way more than just ’mainly one factor’: Its more than just two...
Look at the two distortion charts two posts above. You can clearly see a difference- the Purifi module has the gain bandwidth product to support the 70dB of feedback that module employs. There’s a lot going on there- Bruno has patents regarding the process. Its not ’mainly one factor’- there is a host of factors- poor choice of words on your part??
Since most polystyrene comes from Germany from the same plant.....there was practically nothing different in each custom cap.
The Germans got out of the polystyrene film business about 10-12 years ago. Its now made in China, but the Chinese film is thicker (this according to the prior owner of REL, now retired), resulting in lower performance. Termination of the foil used in the cap makes a difference- this is well documented. There probably were differences in the caps- if they were made with German film or not for starters. I’m sure if you did some measurements a correlation to their sound quality could be found. Usually you don’t have to look very hard to find it.
Many people think that because we make an all-triode class A fully differential zero feedback OTL with only a single stage of gain that the amp is really tweaky. IME they are surprised to discover that real math went into it and measurements confirm the math, and as a result the amps are really consistent and stable. I’ve been challenged by SET fans that it can’t sound right because it cancels even ordered harmonics; but since it has a cubic nonlinearity the higher orders fall off at a higher rate as the order of the harmonic is increased, allowing the 3rd (which is treated by the ear nearly the same as the 2nd harmonic, meaning its innocuous as long as its at a reasonable level) to mask the higher orders.
They are smoother and more detailed than any SET made.
As you can see, there’s a lot more to it than just ’the right distortion signature’; to get that a lot of stuff is going on.
The same is true of any amplifier. If you get the right distortion signature the kind of amp it is becomes irrelevent. There’s nothing special about any of the technologies- DHTs, pentodes, Static Induction Transistors (VFETs), GaNFETs and the like. The trick it that distortion signature. You can arrive there by tweaking, but if you are only using your ears you’re really taking a shot in the dark.
The chief engineer at HH Scott once said "If it measure good and sounds bad, it is bad. If it sounds good and measures bad, you’ve measured the wrong thing."
That statement is very much in play in class D.
