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In Reply to: Ingnorance abounds and your propaganda is baseless. posted by Dan Banquer on March 12, 2007 at 04:38:08:
Your other bald faced lie is that tube amps only give low order distortion. It has been well documented that tube amps give significant and audible amounts of even order distortion, 4th, 6th, 8th etc, etc, order. This gives tubes that typical "muddy" sound, that most audio perverts like yourself, call "musical" It's not musical, it's audible distortion. The fact that illiterate pompous propagandists like your self claim otherwises has the rest of the world ignoring your lies.
d.b.
Follow Ups:
I have test measurements from an independent Dutch magazine that shows that the smaller brother of the amp I am using has at 1 watt only to 5th harmonic above the -125 db level. The 4th and 5th are at -95 db and -105 db the 3rd at -75 db and the 2nd harmonic at -50db.At 10 watts this amp has more harmonics above the -130db level.
2nd -40db
3rd -55db
4th -70db
5th -85db
6th -90db
7th -105db
8th -110db
9th -115db
10th -110db
11th -115db
12th -120dbAs you can see the results are not bad at all for any amp of its power rating and most SS amps have higher levels of higher order harmonics at this power (and more damning at lower powers where my amp gets more and more linear...crossover distortion...its a bitch). Also, above 4th harmonic the levels are still very low even at 10 watts (a lot for a typical SET and plenty for most music listening with reasonably sensitive speakers).
Again, bandwidth is 80khz (-3 db) and damping factor is about 5.5 (fine for all but crazy impedance curves). Distortion vs. frequency is nearly flat.
You are right about one thing, Push pull tube amps with negative feedback do indeed often more give higher order harmonics. They also often give predominantly odd order harmonics like most SS amps (due to even order cancellation from being push pull). Also, tube amps with poorly designed output transformers will have high distortion in the bass usually. This is not endemic to the design but indicative of a poor output transformer choice. Finally, a poor driver stage can generate a lot of distortion as well. It is true that a no feedback amp is more sensitive to these things but with careful design and execution the problem is largely solved not doctored with feedback that really doesn't solve the problem of inherent non-linearity.
Just like you would say that most SS amps are likely poorly designed, so too are many tube and hybrid amps. That doesn't mean the whole class of amp is damned it just takes talent to make it work correctly. IMO, the result sounds better because it makes less offensive distortions...and I think this is largely due to the relative absence of negative feedback.
"that most audio perverts like yourself, call "musical" "
I never call muddy sound musical, Dan. I call muddy sound muddy, and grainy sound grainy etc. In fact I believe there are two types of distortion, the kind you can hear and the kind you can't. If you can hear it then it degrades the sound...period. If you can't hear it then its like it isn't there at all. Doesn't matter if it is 0.00001% or 10%, if you hear it you hear it and if you don't then who cares if its there? If a tube amp sounds muddy then it is clearly making audible distortion. I don't abide by this because I know what real instruments should sound like, period. If an SS amp sounds sterile or grainy in the highs then I don't abide by it because that too is distortion. The question then is which type of distortion is less annoying. The amp I have now, at reasonable levels, has to my ears nothing in the way of distortion. It is one of the only ones i have heard this clean without being etched or sterile.
Actually the fact that such amps are on the rise should give you pause to wonder why people are preferring the sound. After all, according to your design philosophy, we have had perfect amps for at least 25 years. Some have thought about this and come up with better sounding designs. Fossils like you are not flexible enough to question your own philosophy so it is no wonder you rage against the wind, which has shifted direction away from your philosophy. There is a backlash for a reason and its not because we are all degenerates and you are somehow the perfect rational human. Rather it is probably the reverse.
The third, fourth and fifth and possibly sixth harmonics are readily audible. You haven't studied much of anything substantial on audibility and upper order hatrmonic distortion have you? Pretty fair amount of upper order distrtion in your example, makes any reasonably designed solid state look damn good.
Duh!
"Duh"No Duh there Dano. I have seen PLENTY of SS amps with high order harmonics much higher in level and also extending well beyond 20kz for a 1Khz signal (so even over 20th harmonic). In addition, they are mostly odd harmonics...the most offensive.
The third, 4th, and 5th are audible but at what levels? Do you know? 2nd is of course inaudible up to quite high levels but we are talking about -75 db, -95 db, and -100 db at 1 watt. Probably not so audible because masking can still occur for these harmonics (ie. the ear still makes distortion at these harmonics). The complete absence of anything 6th or higher (at least they are below -125 db, which is the measured noise floor above 1khz)is the really interesting story.
At 10 watts those were -55db, -70db and -85 db. HOwever, this will likely be less audible because it will be much louder (with a 95db speaker likely too loud) and your ears own distortion may still mask the distortion (see cheever).
The real problem, Dano, is the higher order harmonics present in a complementary, Class AB amp with high feedback at LOW power, where most listening is really done. Found a cure for that crossover distortion and high order harmonics? Didn't think so. Feedback doesn't fix it, Dano. Feedback MAKES high order distortion, while reducing low order distortion. Read Crowhurst or Boyk and Sussmann.
It is also clear from Boyk and Sussmann's triode tube model why my amp has some low level high order harmonics when the power increases. However; it is clear from their work also that for the same input level the tube produces far lower levels of higher order distortion, which is why at 1 watt they are well below the -125 db noise floor. I think we can both agree that below -125 db it is likely to be inaudible, no?
Crowhurst talks about signal correlated noise floor, something that is really only possible with negative feedback. As the so called "noise floor" is really made of multitudes of harmonic components it will increase and decrease and modulate with the input signal. This can't happen with a no feedback design. What about back EMF distortion from highly reactive speakers? He says that although the level is quite low the high order nature of the distortion could possibly be audible and could be why amps can sound so different from speaker to speaker. Care to comment on that or was Otala a quack too?
Cheever found a way to measure a Hafler DH500 without the feedback interferring and found the THD to be 24%!!! Of course with feedback this amp wipes the floor with yours in terms of THD. I doubt either of us would find it particularly good sounding.
If your distortion measurements are anything like your S/N measurements I'll take those with a few grains of salt too."Cheever found a way to measure a Hafler DH500 without the feedback interferring and found the THD to be 24%!!! Of course with feedback this amp wipes the floor with yours in terms of THD. I doubt either of us would find it particularly good sound."
I would not make that assumption if I were you; and you still don't understand the basics of negative feedback, you refuse to learn and you insist on misinforming others. I guess that makes you well qualified to write for a magazine that gives the CLC a design award.
Have nice day;
d.b.
Why don't you get off your lazy butt and read it for yourself? If you then think he did it wrong then explain why you think he was wrong. Otherwise, I will assume that his data is correct and you don't know what you are talking about.
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