George, what is "low impedance" and what is "true reference point"? Sorry to be harsh, but these are quite empty terms to me.
George,
If we had perfect components and could design & build perfect layouts I might agree with you but we don't & we cant . . . so I don't agree.
Unfortunately, it is impossible to explain to the piece of wire (regardless thickness) that it should have 'low impedance'. The wire is unable to get rid of its inductance 😉
‘True’ goes to ‘common’ reference point.
For "low impedance” see below.
John will come back and write for the nth time that self inductance of a wire is miniscule compared to the inductance of the loop that is formed between this wire and the conductor that the return current decides to ride on it’s way back to the source.
My understanding is that a galvanic coupling to a common point can be made in a way far more predictable than the various ‘hidden’ capacitive and inductive couplings that a floating construction entails.
e.g. (to pick up the line of PMA), an SMPS with floating DC output.
Connect the – DC to the Input Ground connection of the SMPS with a wire passing internally underneath the switching semiconductors.
George
There's a very user-friendly slide presentation of these concepts by Joffe, "Current, if not Obstructed, will always Flow in the “Path of Least …". It seems to not be so easily available at the moment, unfortunately ...
Gotta love this Joffe bloke - another piece is "Can Just Anyone Understand Maxwell's Equations, or - Who's Afraid of Maxwell's Equations?" ... 😀
What is of interest here, is that there is another very famous and highly regarded designer . . . If you look inside his amps, there's hardly anything in there. A few JFETs, some output mosfets and a PSU.
Distortion on his designs is for the most part above 0.01%. His amps cost upwards of $10k each and he regularly gets rave reviews - including from Stereophile.
To SY's point, this really is a luxury, fashion business, not to be confused with engineering or good design - an altogether different field of endeavor.
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Bonsai are you saying the audio business is devoid of engineering and good design, thats really absurd ....
Bear's amp was I believe his implimentation of a Borbely power amp ( possibly the DC 102 or higher output derivation).
Bear contributed the mechanical packaging, oversized power supply, and large heatsinks to allow a fairly high bias current
Bear contributed the mechanical packaging, oversized power supply, and large heatsinks to allow a fairly high bias current
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Audio Critic is not the only magazine that measures load stability. Audio does that at least since 30 years. There is more to it. Quantifying sound ? If we could do that big progress could be made. How can you measure QUALITY though ?
http://www.audio.de/ratgeber/3/5/0/7/2/0/Die_AUDIO-Kennzahl.pdf
http://www.audio.de/ratgeber/3/5/0/7/2/0/Die_AUDIO-Kennzahl.pdf
Bonsai, it is not important to get below 0.01%, as it is inaudible. The designer probably knows what he is doing. Avoiding unnecessary circuit complexity, danger of invisible local oscillations, EMI susceptibility. Fight for ppm's is useless. It counts only on paper or in simulation competition.
Measuring quality.
You define or describe qualities or attributes and then test to see if they have subjective import.
See Olive, Toole, Griesinger, Usher, Geddes.
As an example, a quality that, as far as I know, has not been subjectively tested (formally) might be an amplifier's recovery time from clipping.
[Edit] Physical quality testing is an ordinary engineering procedure.
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Revel speakers past the Toole test just fine. Are they the best speakers in the world ?
For example, having a L/R4 crossover they distort step response gross.
For example, having a L/R4 crossover they distort step response gross.
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