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DVDdoug

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I'm pretty sure McIntosh tube amps don't have audible distortion (unless overdriven) and has no sound of it's own just like any good amplifier.

with greater actual detail rather than brightness masquerading as detail.


But tubes have measurably greater distortion- so how is this possible?
I always assume "detail" means boosted highs. But Dan Clark (headphone manufacturer) has mentioned that headphones with more distortion are often described has having more detail.

The famous-old Aphex Aural Exciter adds high frequency harmonics (harmonic distortion) but it's a production tool, not a reproduction tool.

I like try avoid terminology like "detail" or "musical" or even "warm" (which has more than one meaning) or any of that "audiophile" terminology. I try to stick to real characteristics... noise, distortion, and frequency response.

With modern solid state electronics, distortion is pretty-much a solved problem. Flat frequency response is easy too. Usually if there are any audible issues/defects (with electronics) it's noise.
 

dfuller

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It also has to do with how the ear perceives distortion, and in this case I'm talking about distortion where the amplifier is not being overloaded. The ear interprets the 2nd and 3rd harmonics as 'body', 'warmth', 'fullness' and the like, all terms to describe their presence. If these harmonics are present in sufficient quantity, they will mask the presence of the higher orders. Since tube amps generally have more of the lower orders (2nd, 3rd and 4th) than solid state amps, the result is that the higher orders are masked and so tubes sound smoother even though they have greater higher ordered harmonic content than solid state.
This part has a grain of truth to it because of the way masking works.

Our brains interpret sound in critical bands, and lower order harmonics are generally close enough to the fundamental to be largely inaudible except in grossly huge levels.
This is why speakers can have 3% distortion at times and still generally sound pretty clean - 3% HD with it almost entirely consisting of H2 is pretty much not audible as distortion.

Higher orders, not so much. They are audible much quicker because they're far less likely to be in the same critical band.

The lower orders, if in sufficient quantity, also contribute to soundstage width and depth, as well as lower level detail!
Now this, this is bullshit.
 

Rednaxela

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Any input regarding the statement from Ralph and Nelson Pass Designs?
It reads like the usual subjectivist audio hogwash.

In general I’d be careful with anything that leads to feelings like these:
I think perhaps there’s more to sound than many people realize.

What’s so hard about going for the cleanest amp that meets your needs? This is a rhetorical question. No answer required. :)
 

levimax

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Does the feedback increase the ABSOLUTE level of higher order harmonic distortion, or the RELATIVE level of higher order harmonic distortion .... meaning "relative to the lower orders"?

Jim
From Bruno Putzey's Article, moderate amounts of feedback do create higher levels of higher order harmonics.

Negative feedback in audio amplifiers: Why there is no such thing as too much (Part 2)​


Storyline 2: Re-entrant distortion
I said earlier that the error is signal dependent. In 1978, Baxandall noted that negative feedback around simple nonlinearities creates distortion components that weren't there before (Figure 14).



media-1196235-negative-feedback-2-fig14.jpg


Figure 14: Spectral decomposition of the output of Figure 15 as a function of A (dB).
Top to bottom: fundamental, 2nd harmonic, 3rd harmonic, etc.
 

kongwee

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Does the feedback increase the ABSOLUTE level of higher order harmonic distortion, or the RELATIVE level of higher order harmonic distortion .... meaning "relative to the lower orders"?

Jim
 

amirm

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I have tested and listened to many tube amps. If they soften the sound, it is because they have high impedance and interact with frequency response of the speaker to get there. And not because of any distortion profile. Speaking of distortion, I readily hear it at almost any level. It starts to first muddle the sound with instruments no longer being separated and then severe distortion sets in. If you are not sensitive to it, you may not hear it or bothered by it. But again, it is not revealing anything. People look at the warm glow of the tubes and imagine all kinds of positive effects. For me, it is always a relief to go back to a powerful solid state amplifier.

I should say that I imagine you can design a much cleaner tube amp than much of what gets released in audiophile market.
 

levimax

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I see.
It appears, then, that the solution is to increase negative feedback, not reduce it. Similar to cleaning windows with ammonia; a moderate amount cleans the dirt but introduces streaks that weren't there before. Keep wiping the window - more vigorously - and the streaks disappear, leaving a window that is clean and streak-free.

Jim

Jim
This article was an eye opener for me when I read it some years ago and it put me on a path to learn more about the science of audio rather than the mythology. Interesting that the most common amp designs with "moderate" feedback of 20 to 25 dB are actually the worst at producing higher order harmonics that didn't previously exists, audibility is of course another question. The problem is adding high amounts of negative feedback requires very high open loop gain and is fraught with stability issues. @tomchr from Nuerochrome has managed to get it to work and the performance of his amps speak for themselves.
 

wwenze

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Or we can have a solid-state amp that is like a tube amp :p


Add some salt and output impedance to taste
 

antcollinet

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That article is self-serving garbage with no third-party documentation or list of controls. In particyular, I'd like to know the details that led to this statement: " ... Anecdotally, it appears that preferences break out roughly into a third of customers liking 2nd harmonic types, a third liking 3rd harmonic, and the remainder liking neither or both. Customers have also been known to change their mind over a period of time. ..."

Jim
They clearly state the details : "Anecdotally"

In other words they sit around telling each other stories. Perhaps over a beer. It has as much in common with documented reality, as Harry Potter and the Philosophers Stone.
 

FeelinNoPain

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I see they don’t make a preamplifier. Any suggestions? I like the idea of sticking with one company for both.
I’ve got the “Benchmark trio”: DAC3B, LA4, and the AHB2 amp. Love ‘em. Very transparent. They’ll definitely reveal a crappy recording, but will also reveal a good recording just beautifully.
 

Mr. Widget

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People look at the warm glow of the tubes and imagine all kinds of positive effects. For me, it is always a relief to go back to a powerful solid state amplifier.
Agreed on the potential sighted bias big time with the glowing tubes. The only tube gear that I have kept is a Marantz 7 that very carefully hides its tubes in RF shielding. For a 1959 design it is pretty stellar... by today's standards we can do better. I keep mine for nostalgia not for its audiophile magic.

Beyond sighted bias and fooling oneself, I think there is a fundamental question. Do we want laboratory accuracy or a pleasant sound? I think we can have both, but am not sure everyone would agree.
 

SSS

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I should point something out here. The big difference between tubes and transistors is that tubes tend to sound smoother, with greater actual detail rather than brightness masquerading as detail.


But tubes have measurably greater distortion- so how is this possible?

The answer has something to do with the ear's masking principle; that is where a louder sound can mask the presence of a quieter sound.

It also has to do with how the ear perceives distortion, and in this case I'm talking about distortion where the amplifier is not being overloaded. The ear interprets the 2nd and 3rd harmonics as 'body', 'warmth', 'fullness' and the like, all terms to describe their presence. If these harmonics are present in sufficient quantity, they will mask the presence of the higher orders. Since tube amps generally have more of the lower orders (2nd, 3rd and 4th) than solid state amps, the result is that the higher orders are masked and so tubes sound smoother even though they have greater higher ordered harmonic content than solid state.


So solid state tends to sound brighter and harsher (harder) than tubes because the ear interprets the higher orders in this manner, simply on account of the fact that the higher ordered harmonics (to which the ear is keenly sensitive as it uses them to gauge sound pressure) are exposed.


But there is more, and this bit is really fascinating. The lower orders, if in sufficient quantity, also contribute to soundstage width and depth, as well as lower level detail! This is why tube amps tend to have a wider and deeper soundstage than solid state. Oddly, this is not an exaggeration, but in order to understand that this is so it is helpful to have master tapes or files and also to have been present at the recording to know how it is supposed to sound.

The bottom line is this: unless the amplifier has **no** distortion and by that I really mean no distortion at all and not just vanishingly low, the inclusion of a bit of 2nd and 3rd in sufficient quantity can actually result in the amplifier sounding more 'neutral' to the human ear. Again, this is a topic that deserves more research, but this phenomena has been known for quite some time.


So its going a bit out on a limb to use the word 'accuracy' as in the comment below.


Put another way, if the amplifier designer is aware of how the human hearing perceptual rules work, and is pragmatic about the simple fact that building an amplifier that truly has no distortion is impossible, then the next best thing to do is to include some of the lower harmonics for the perceived benefit they bring, even though it might look bad on the spec sheet. In this way its easy to show that the spec sheets are a good example of the Emperor's New Clothes, as for the most part they ignore human hearing perceptual rules as they have been ascertained in the last 40 years.


Nelson Pass seems to have sorted this out. He is one of the few solid state designers to have done so, and no surprise, his amps sound more 'natural', 'neutral' and musical (IMO) than his competition with lower distortion as a result.

shannere

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04-01-2020
Did find this today. What a hell of stereotype opinion put as fact. Warmer - harsher (what does it mean) are attributes and can be right for tube amps as well for transistor amps. It is a question of electronic design what sound (if any difference) comes out at the end. Early tube amps sounded not good when driven hard and it may be true also for todays gear. One difference between transistor and tube type amps is that tubes have the lowest distortion at lowest volume where transistor amps have relatively high distortion at very low volume due to design of the circuit. Thanks that the ear/brain system is forgiving much because many natural non-music sound has harmonics and disharmonics as also some musical instruments.
 
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