John Curl's Blowtorch preamplifier

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#8,201
rdf asked

Does 'spread harmonically' mean physically stagger the spacing between decoupling caps along the electrical length of traces to avoid standing waves on the power supply buss?
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Yes. The resonances occur between the PWR and GND planes. It usually doesn't take too much effort to push the resonant frequencies high enough to be of little concern. Certainly not difficult when you know what you are aiming to do.

And Jan Didden has kindly just posted the articles on his website that I referred to earlier and was looking for . I have the originals but couldn't remember where I got them from - probably a tech-on-line feature.

Please read these - they are very informative.
 
#8,205
john curl said:
VivaVee, your link provided the question that I have at this time. E.G. is the .1uF default bypass cap obsolete? I certainly would wish it to be true. It would depend on the real contribution that the bypass does and at what frequency. I hope that Scott Wurcer will give us more complete input on this. I know that he has greater understanding than most, because he helped me 24 years ago with a bypassing problem with an RF amp. He has done significant research on the subject.
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Actually I scavanged one of the best bypass caps I ever used off of 1970's Honneywell HSTTL boards. They were 2.2uF ceramic and could stop just about anything without something smaller in parallel. One of the issues in caps these days is what is the largest value in the smallest SMT footprint.

At RF caps figure a lot into minimizing distortion were you don't have PSRR to help. There are four expensive and large film caps in every ADSL modem since -60dBc was the best they could do without them.

At audio I remain skeptical that the <-120 dB stuff left has any bearing on the perceived sound. From what I read a lot of folks like Dr. Geddes' work so why not repeat his computer generated distortion tests keeping the max THD's below -120dB? I admit to only having skimmed his results but I thought the perception threshholds were quite large.
 
#8,206
mrjam said:
Tino,
thanks for having posted the link to my research!

I hope it could be useful for someone on this amazing thread.
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You have an enormous about of work in that report. I'm always in awe of anyone with the patience to go that far fully documented. I usually get distrated soon after I start. However I couldn't find any details on the test conditions or instruments. I would appreciate those details. Any pictures of the setup would also help.
 
#8,208
scott wurcer said:
At audio I remain skeptical that the <-120 dB stuff left has any bearing on the perceived sound.
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now, some believe in extra terristerial = ET (from outer space)
others do not - more down to earth = grounded in facts


where would we put this poor john curl? .. on a scale
one ET believer or more down to earth and the muddy soil we all dwell in

😕 john curl is a mystery to me 😕
he takes care of any microscopic detail of technical construction
yet, he believes he can listen and decide his designs details from there


Lineup - really do not get this man called john curl
but still he wouln't want to miss john curl opinions on audio
Regards to all music lovers 😎 named john or anything else more fancy
 
#8,212
PMA said:
Regarding -120dB, I am pretty sure we shall have to revise our standards soon. IMHO, according to my experience, -120dB (or -115, -125, who knows exactly) of high order harmonics like 7th, 9th, 11th .... contributes to subjectively worse "sound", compared to gear with "unmeasurable" high order harmonics.
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The question is
are we actually hearing the distortion, or is the THD merely an indicator of something else which we do not measure for yet
 
#8,213
Thank you for making a clear claim. I would like to be one of those proverbial "everyone in the room" that agrees that this is so. If skeptics are excluded from the tests then they lose validity. ABX is not necessary, but taking things into your own private listening room and "living with them" is hard to monitor.

The claims have been made here OTOH that the difference was so immediately obvious that listening to the other choice was not even necessary, in a case where certainly the differences were at the ppm level if even that.
 
#8,215
myhrrhleine said:


The question is
are we actually hearing the distortion, or is the THD merely an indicator of something else which we do not measure for yet
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The degrees of freedom for two time varying voltages are limited, so again we are faced with opening the door for some unknown physics that somehow applies to audio but has been somehow missed by other fields. Again show me some high resolution instrumentation in another industry enhanced by "brilliant pebbles" or Shatki stones or whatever.
 
#8,220
PMA said:
The "known physics" is the problem, as it was many times in history. Many discoveries were declared as "impossible" according to current standards. Closed mind does not allow any new observation, in case it violates contemporary knowledge.
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Pavel,

Many discveries were made by meticulous observation, testing and validation, disclosure of full test setups, and by giving others the opportunity to repeat them and come to the same conclusion (good!) or not be able to reproduce the phenomenon.

What you and others here give are armchair anecdotes followed by the exclamation: 'prove that it cannot be the case'!
If it wasn't so sad, to hear this from someone who purports to be a logical man of technology, it would be hilarious.

Jan Didden
 
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