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Old 29th September 2005, 03:48 PM   #41
lumanauw is offline lumanauw  Indonesia
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Hi, Mauro,

Long time no see

Yes, I notice that the more you put poles everywhere in the cct, the sound will become "dead". Maybe it is super stable, but not nice to listen to.

I think I recall that someone here is experimenting a design that has pole,zero,pole,zero in the whole loop. I don't remember who it is, but with this experience, maybe that kind of approach can be good sounding. Sure it is difficult to intentionally put zero anywhere, but wanting the whole amp to be stable. It's kind of standing on the edge of a cliff. You can see the whole beautiful scenary, but if you are not carefull, you will fall down.
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Old 29th September 2005, 04:21 PM   #42
mauropenasa is offline mauropenasa  Italy
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Hi, Lumanauw

Yes, more time...

The main point is doesn't concentrate only on the stability.
If you are aware that serve avoid the standard compensations, the way finds.
A lot of planners have developed a linear compensation techniques. Enough chooses that more applicable to the circuit.
For example, Graham has used techniques distinct from my, on his amp, but the instrumental result (DF linearity) can be similar...


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Old 29th September 2005, 07:27 PM   #43
Miles Prower is offline Miles Prower  United States
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This assertion ("sounds better"... so repetitivly seen) is typical of what I call an inobjective comment.

Yes, it is "unobjective", but that alone does not make the matter unimportant in and of itself. In many cases, "unobjective" simply means that we don't yet have complete information concerning the phenomonon in question.

This is my biggest disagreement with Mr. Self: his attitude that if you can't measure it, then it's not important. He's making the same mistake as the "subjectivists", but from the opposite direction. Audio design (all electronic design in fact) is science + art. You need both or you will never get anywhere. You can measure DC bias levels, o'scope the output while running all sorts of waveforms through it, analyse distortion till the cows come home. In the final analysis, you have to connect the speeks and listen to the durn thing to see if all that scientific analysis has led you to what you were trying to accomplish in the first place. That, by definition, is subjective.

It is absolutely false that it sounds better, it is absolutely true you prefer the sound of Ollsen's amplifer (a huge lot of difference !)

A difference without a distinction. When I started the project, I certainly wasn't intending to use a quasi-complementary final. That whole topology just looks ugly right on the schematic. I decided to go with it for the main reason that one of the design objectives was that one could get everything needed to construct the circuit from the neighbourhood "Rat Shack". (And at the time, I had never heard of either Self or Ollsen.) They've been giving the do-it-yourselfer the shaft for years now, and they just don't have a decent selection of matched pairs of complementary power BJTs. So I tried doing it both ways to see if the quasi-comp would give acceptable results. Turned out that it worked better despite the nominally higher THD. There's probably an explanation for that out there waiting to be discovered.

I am not aware of IC's désigned for good sound and not having very good specs and a lot of feedback. And there usually are some IC's at the recording stage. Do they make so much harm to the perceived sound ?

And in the vast majority of cases those ICs are working into consistant, well characterized, loads. Powering up speakers is a whole 'nother story.
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Old 20th January 2013, 07:39 PM   #44
kad is offline kad  Canada
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Arrow Biasing and Hysteresis

This interesting thread makes me think of bias and hysteresis concepts?

It is not an attempt to delve into to the subjective “ultimate” term as experienced by various individuals.

In the end, all that matters to individual audiophiles are not a wide variety of individual personal preferences; but what one considers “oh wow!” If one tremendously enjoys the proceeds of what they have accomplished, then they have succeeded in achieving their “ultimate” performance quality. Anything less would be uncivilized?

My perspective is that through science and technology, one can attempt to seek better understanding of the underlying fundamental concepts influencing the quest towards this “ultimate” performance.

This begs the question: Why? For me that objective is simple: Just for fun and satisfaction.

Now onto the brainstorming session.

First, I think there is nothing right or wrong with distortion. Elsewhere someone related to the term ‘deviation’ over the colloquial term ‘distortion’. A concept I find intriguing and perplexing.

Metaphorically, just like ‘variety is the spice of life’; spice is a form of deviation from the ‘pure’ ingredient, meant to enhancing its flavour and harmony. Some like spice, others don’t. That doesn’t make either right or wrong. In its barest essence, all great chefs cook up great tasting dishes, by adding in their own passions, visions and experiences.

Since I believe one of the audiophile quests is to mainly experience pleasurable sensations generally recreated through reproduction of musical performances, in the comfort of your own home, at the convenient moment one desires so. This requires recording the performance (something done by the artists playing music). Then one must be able to recreate exactly what was recorded at a different time into their own environments.

Hence science and technology have provided us various methods by which a musical performance is ‘transduced’ from one form to another. Basically a sound is mere atmospheric pressure changes, captured by a microphone, which then is transformed into an electrical signal, which is then massaged into a suitable archiving method (digital bit-stream, or analog grooves onto an LP).

One of our main focuses as audiophiles is to ‘transduce’ this recording back to mere sound. In order to take minute levels of recorded information then massage it back into an appropriate form for further reproduction, we require amplification of these low-amplitude signals and ultimately drive our speakers (transducers) which might be regarded as the opposite of microphones. But both of which are using the exact same universal physical scientific principles in a reciprocal manner.

Since both microphones and loudspeakers are generally based on transducing sound to electricity and vice versa, they both share in common the use of magnetism and electricity as a transconducting function.

While attempting to deconstruct the fundamental forces at play down to the lowest-common-denominator (LCD), it appears to me distortion is merely a ‘spice’ that either enhances for some, or detracts for others; the ultimate experience of enjoying their musical experiences.

From a technical standpoint, it is interesting to investigate the limits of magnetism, since it is such an integral part of the LCD. This in turn leads further deeper examination of similar forces at play in the electrical as well as physical domains.

Unfortunately, I cannot propose a solution (yet), merely only raise some of the questions which might help us truly understand then focus onto the fundamental principles involved how to achieve each individual’s perception of “ultimate”.

Basically I am sharing the belief that there is nothing wrong either with spices or distortion. But we might also focus onto these two fundamental principles to help advance sound reproduction as it relates to electrical amplification and magnetic transducers:
  1. Biasing
  2. Hysteresis
Interesting references:In conclusion, my philosophy focuses on Mark Levinson’s metaphor: “A straight wire with gain”. I personally believe that faithfully reproducing the original source with the minimum possible amount of deviation, is the goal here. At least for me.

Work is the meat of life, pleasure the dessert.
~ B.C. Forbes, 1880-1954, Scottish-born Financial Journalist and Author

There is nothing new under the sun, but there are lots of old things we don't know.
~ Ambrose Bierce

The outcome of any serious research can only be to make two questions grow where only one grew before.
~ Thorstein Veblen

A successful life is one that is lived through understanding and pursuing one's own path, not chasing after the dreams of others.
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