John Curl's Blowtorch preamplifier part II

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IMO, in the phrase: “a common polluted point of reference for all the circuits in the chain”, the emphasis should be placed at the ‘common’ rather than at the ‘polluted’.

If all the connections to this common point were of very low impedance (thus this point was a true reference common point), pollution there would have no operational consequence.

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.
 
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George, what is "low impedance" and what is "true reference point"? Sorry to be harsh, but these are quite empty terms to me.

‘True’ goes to ‘common’ reference point.
For "low impedance” see below.

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 ;)

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.


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.

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
 
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SY, you know nothing about the audio business. I deeply resent your input on what you are not qualified to have such strong opinions on.

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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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.

Trolling, heh?
 
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.

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.
 
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

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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