John Curl's Blowtorch preamplifier part II - Page 2936 - diyAudio
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Old 16th November 2012, 05:58 PM   #29351
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Hi John
Ok, you caught my ear here, Dick was an inspiration for me and I am an early TEF user. My friend and co-worker Doug Jones was the curator of the Heyser library when he taught at Columbia College and I was lucky to be able to poke through it and read some of his unpublished papers. I met him one time, Don and Carolyn Davis asked me if I wanted to walk with them (at an AES show) and that turned into a dinner with them and a number of others in audio including Dick. I said about three words all night and that only when Don threw me a slow pitch about the Servodrive subs.
While he is terribly under appreciated by the AES, for me he changed my life in sound or at least his TEF machine .

Anyway, if you can bare to go through it again, I promise I won’t hoot and holler.
Fwiw, I have seen (with an HP-3562) loudspeakers where the distortion was both reduced and increased (depending on the harmonic) due to vector addition with the drive amplifiers harmonics.
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Tom
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Old 16th November 2012, 06:02 PM   #29352
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Quote:
Originally Posted by john curl View Post
Yes, I am very open minded.
Again, with all my sympathy, you cannot decide of that, everybody think he is open minded.
Only others can judge of that.
'Open minded' does not mean, i believe, some try his best, but he is able to consider other's thoughts and try to understand how and why they can differ from his own ( or correlate ) and try to find some food in it.
Of course, this assumes a minimum of sympathy, consideration, respect and courtesy to others.
And, when some feel the need to demonstrate something, his words are like wind. Nobody cares about faiths of others.
Demonstration is the minimal exercise and let people decide by themselves, a minimal respect to their intelligence.
How can-we get some respect from others if we do not give any to others ?

May-i give an example ? Why the Bob Cordell's demonstration of the importance of amp's 'speed' in regard of TIM had so much influence in the audio world ?
Not because he discovered something revolutionary, many people were fighting to increase open loop bandwidth in servo systems since long years, it is just because he demonstrated its correlation with TIM in a very scientific, clear and modest approach with no ego.
And that will not give-him more credit for future assertions, since i'm sure he will not assert but, again, demonstrate.
Names are not references, only numbers and logic. And AES just a little private club.
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Last edited by Esperado; 16th November 2012 at 06:15 PM.
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Old 16th November 2012, 06:16 PM   #29353
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Esperado, I will not debate with you about 'open-mindedness'. For me, the definition of 'open-minded' is to NOT judge without real evidence, something that might be potentially controversial.
Are you sure about Bob Cordell's argument? Open loop bandwidth is an OTALA-CURL fantasy, not a Bob Cordell one. He just makes a fast amp, 200V/us as I recall. I know Bob better than you do, so to compare Bob to me is laughable, with the opinions that you have stated.
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Old 16th November 2012, 06:34 PM   #29354
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so to compare Bob to me is laughable
Yes, i think many will laugh, but not for the reason you think.
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Old 16th November 2012, 06:51 PM   #29355
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I've said this before on this thread more than once,
but feel compelled to say it one more time.
Except in special cases .............
DISTORTION DOES NOT MASK DISTORTION !
All this BS about 100 opamps in the studio or
the speakers are even worse is just that.
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Old 16th November 2012, 07:01 PM   #29356
qusp is offline qusp  Australia
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yeah I would have thought it would be a series thing too, obviously its not all correlated, but I would expect it to add
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Old 16th November 2012, 07:02 PM   #29357
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Quote:
Originally Posted by hitsware View Post
DISTORTION DOES NOT MASK DISTORTION !
All this BS about 100 opamps in the studio or
the speakers are even worse is just that.

How about un-masking. Still waiting, we haven't diverged into a sub-thread planning the great listening test in a while.
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Old 16th November 2012, 07:04 PM   #29358
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Quote:
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yeah I would have thought it would be a series thing too, obviously its not all correlated, but I would expect it to add
No, I think the idea is that a speaker with percents of 2nd's and 3rd's does not mask the op-amp in front of it with -100dB of each.

BTW - please John repeat Dick's comment in detail you have done nothing but allude to it as far back as I can recall.
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Last edited by scott wurcer; 16th November 2012 at 07:07 PM.
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Old 16th November 2012, 08:05 PM   #29359
PMA is offline PMA  Europe
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Quote:
Originally Posted by hitsware View Post
I've said this before on this thread more than once,
but feel compelled to say it one more time.
Except in special cases .............
DISTORTION DOES NOT MASK DISTORTION !
All this BS about 100 opamps in the studio or
the speakers are even worse is just that.
Well, I think speaker distortion masks any distortion of well designed amplifier. Anywhere, even for "high order" components. Recently I made a large set of FFT measurements at acoustical side, i.e. with microphone at listening place. Change of two amplifiers that measure different electrically, but below 0.01%, made absolutely no difference in FFT spectrum of harmonic distortion and ccif imd. To me, nonlinear distortion is not an answer of different sound of well designed amplifiers.
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Old 16th November 2012, 08:11 PM   #29360
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Default Take the entire record/reproduce system into account -

Quote:
Originally Posted by scott wurcer View Post
The total will always involve random vector addition and approach a root sum of squares not linear addition so to get from -100dB to -80dB you would need 100 components in series. No speaker even approaches these numbers anyway. We also know how to make amplifiers that are second and third harmonic dominated by a wide margin. I don't see THD factoring into the sound of anything unless it is the "sound".

BTW where in Vol. 4? I don't remember anything but anecdotal references.
Hmmm. seemed to have missed my point somewhere.... we want to have -100 in all the electronic amplifying/buffering stages (up to a hundred of them from recording source to speaker amp) just so it isnt audible and never will be.

I take the view of designing to the the worse case where they Do all add up. Never-the -less, in the here and now- with millions of existing record/reproduce systems and with millions of combinations of all possible -old and new - hardware, there is a substantial number that have audible levels of distortion. [Since we are mostly talking about electronic designs here.. I am leaving out speakers.] That's all.... dont read more into it than is here/there.

-RNM

Last edited by RNMarsh; 16th November 2012 at 08:36 PM.
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