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Old 1st February 2009, 02:48 AM   #13681
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Quote:
Originally posted by JPV



Sorry edit error.



Does it make sense to use capacitance multipliers to power the front end and Vas of a power amplifier.

Is it realistic to investigate the replacement by a capacitance multiplier of the large and expensive electrolytics of the output stage in a class AB amplifier.
What about the large pulses of current?
Will it sound better?

JPV
Hi JPV,

Yes, it does indeed make sense to use capacitance multipliers in the supply rails to the input stage and VAS of a solid state amplifier, as long as the resulting voltage drop can be afforded. When one uses boosted rails for the VAS and input stage, such a slight additional voltage drop is definitely affordable. If we are talking about very high quality amplifiers, no one should be complaining about the slight extra cost of boosted rails. Note that a capacitance multiplier allows really good filtering of the input and VAS rails without dumping rail noise current into a potentially sensitive ground through brute-force capacitance.

With regard to output stages, I have often thought that a MOSFET capacitance multiplier ("soft rail regulation") between the raw rectified rail and the supply for the output stage would make sense. This capacitance multiplier would still feed into a fairly large capacitance local to the output transistors themselves (perhaps 10-20,000 uF). This keeps raw ripple and RFI away from the output stage. The price paid here is some power supply rail voltage loss ( a precious commodity) and some power dissipation in the capacitance multiplier. The key advantage of this as compared with a fully regulated supply to the output stage is that the voltage provided by the capacitance multiplier tracks the available raw rail voltage, keeping regulator dissipation down and retaining the advantage of dynamic headroom.

In any approach like this, one must always consider whether the output stage would have been just better off with the greater headroom afforded by the same raw supply with the conventional approach.

Cheers,
Bob
 
Old 1st February 2009, 05:16 AM   #13682
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All Parasound power amps in my design range have cap multipliers in the driver stages.
 
Old 1st February 2009, 06:47 AM   #13683
PMA is offline PMA  Europe
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Quote:
Originally posted by john curl
PMA, I also think that Scott's cap' improver' is also important, BUT I don't like that particular topology, especially with discrete, as we have a choice about topology, when we build it ourselves. This is not about distortion or feedback, per se.
I agree, and my experience is quite similar. Maybe I would say "This is not about distortion only "
I mean that distortion should be under certain level, should have certain harmonic spectrum, with only low order components. If this is fullfilled, then it is of minor importance. I still cannot admit distortion produced by vast majority of SE triode amps, not only from technical point of view, but their sound does not satisfy me.
 
Old 1st February 2009, 08:20 AM   #13684
JPV is offline JPV  Belgium
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Quote:
Originally posted by scott wurcer


There is no perfect sound. There are people here who love planar electrostatics and those that love ultra efficient horns, what could be more different?
On this topic, I would strongly recommend the reading of Toole's book. It shows the real complexity of this quest. He puts together a good compilation of a rather scattered topic.
Difficult after that to trust yours ears as main test tool.

JPV
 
Old 1st February 2009, 08:55 AM   #13685
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Quote:
Originally posted by JPV


On this topic, I would strongly recommend the reading of Toole's book. It shows the real complexity of this quest. He puts together a good compilation of a rather scattered topic.
Difficult after that to trust yours ears as main test tool.

JPV

Floyd Toole's book should be mandatory reading here

It's funny how things you 'always knew to be true' can suddenly take on a different perspective.

Jan Didden
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Old 1st February 2009, 03:18 PM   #13686
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Quote:
Originally posted by JPV
Difficult after that to trust yours ears as main test tool.
If you can't trust your ears, then you don't have much reason to be
measuring audio, either.

 
Old 1st February 2009, 05:58 PM   #13687
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Quote:
Originally posted by Nelson Pass
If you can't trust your ears, then you don't have much reason to be
measuring audio, either.
This is not strictly a "yes/no" proposition, despite extreme views on either side. In my view, those who never trust their ears are probably deaf, and those who unconditionally trust their ears are probably delusional. In the real world in the middle, it's a matter of degree. If we are trying to detect some change, then the extent to which we can trust our ears depends heavily on the magnitude of that change.
 
Old 1st February 2009, 06:35 PM   #13688
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I don't necessarily trust my own ears. I trust other peoples ears. Independent, but enlightened opinion, by serious music listeners, is my true feedback, beyond theory and measurement.
I, in turn, can review other designs, from serious (and maybe not so serious) audio designers.
For example, when I heard the LAMM exhibit at CES this year, I KNEW it was a winner and it was only driving a direct radiator speaker system.
The year before at CES it was a similar single ended tube amp driving a horn loaded system.
The year or so before that, we shared a listening room with my electronics driving big electrostatic speakers, that did very well.
I find it just about impossible to qualify any speaker type, or amp type, and state that it is impossible to get wonderful sound quality.
What seems to make the difference, is the care and effort in the design itself, more that the design approach.
For example, the next biggest surprise at CES was a class D amplifier exhibit based on TI modules, but sponsored by IR. It sounded pretty darn good, although I would have to have more time with it to know if something would be distractingly annoying after long term listening. Only time will tell with that one.
 
Old 1st February 2009, 06:53 PM   #13689
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I ask this question about Floyd Toole and his book.
First, I have met and discussed audio with Dr. Toole. I have also attended several of his lectures.
However, what audio components has Dr. Toole found that audiophiles here, have tried and swear by? Any breakthroughs from HK or its possessions?
Let's find what Dr. Toole has found, in REAL PRODUCT, and discuss its qualities and perhaps its limitations.
Then, maybe, we might find the limits of DB testing, in that discussion.
 
Old 1st February 2009, 08:52 PM   #13690
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Anybody own new JBL loudspeakers? Seems to be a favorite of Dr. Toole.
Axiom? Infinity (new)?
 

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