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Old 18th August 2008, 08:28 AM   #8201
VivaVee is offline VivaVee  New Zealand
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rdf asked

Quote:
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?
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.
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Old 18th August 2008, 11:02 AM   #8202
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Default Bypassing

This guy did an awesome work and measured over 200 bypass cap (and chokes etc.) combinations.
Incredible source!

http://www.diyhifi.org/forums/viewto...p=25044#p25044

or direct link to file:
http://www.audiofaidate.it/forum/upl...caps_tests.zip

Ciao
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Old 18th August 2008, 12:09 PM   #8203
mrjam is offline mrjam  Italy
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Tino,
thanks for having posted the link to my research!

I hope it could be useful for someone on this amazing thread.
 
Old 18th August 2008, 01:49 PM   #8204
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Default Bypass

Quote:
Originally posted by mrjam
Tino,
thanks for having posted the link to my research!

I hope it could be useful for someone on this amazing thread.
Hey, just tell me what cap type (ceramic, polyprop, PSS, Teflon or anything) and what value I must use on the opamp supply pins. I am NOT gonna read all that articles again! And maybe also on discrete opamp??
 
Old 18th August 2008, 01:54 PM   #8205
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Quote:
Originally posted by john curl
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.
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.
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Old 18th August 2008, 02:12 PM   #8206
1audio is online now 1audio  United States
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Quote:
Originally posted by mrjam
Tino,
thanks for having posted the link to my research!

I hope it could be useful for someone on this amazing thread.
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.
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Old 18th August 2008, 02:25 PM   #8207
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Quote:
thanks for having posted the link to my research!
Roberto, please post the zip also here! Not everybody is registered at italian forums

Thank you very much! Have fun, Hannes
 
Old 18th August 2008, 03:13 PM   #8208
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Quote:
Originally posted by scott wurcer
At audio I remain skeptical that the <-120 dB stuff left has any bearing on the perceived sound.
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
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Old 18th August 2008, 05:10 PM   #8209
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Quote:
Originally posted by VivaVee
...located adjacent to the supply pin and routed to the ground plane on your multilayer (4 layers if you are cheap, 6 layers acceptable at a pinch) PCB.
You can hear a difference between 4 and 6 layer PCBs?
interesting!
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Old 18th August 2008, 05:20 PM   #8210
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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.
 
Old 18th August 2008, 05:39 PM   #8211
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Quote:
Originally posted by PMA
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.
Edit: :bs:
 
Old 18th August 2008, 06:33 PM   #8212
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Quote:
Originally posted by PMA
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.
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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Old 18th August 2008, 06:34 PM   #8213
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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.
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Old 18th August 2008, 06:40 PM   #8214
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Quote:
Originally posted by myhrrhleine


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

 
Old 18th August 2008, 06:44 PM   #8215
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Quote:
Originally posted by myhrrhleine


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
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.
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Old 18th August 2008, 06:49 PM   #8216
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Background (noise?) modulation?
 
Old 18th August 2008, 06:56 PM   #8217
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Quote:
Originally posted by scott wurcer

we are faced with opening the door for some unknown physics that somehow applies to audio but has been somehow missed by other fields.
Wrong. In fact, by accepting this, we are faced with closing the door for some known physics.
 
Old 18th August 2008, 07:03 PM   #8218
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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.
 
Old 18th August 2008, 07:09 PM   #8219
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Quote:
Originally posted by PMA
Background (noise?) modulation?
All contained in the voltage vs time description of our signals. If something manifests as -130dB IMD but is modulating the noise floor at -80dB (just to make up a case) then we are not doing a good job with our instruments since this is already easily measurable.
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Old 18th August 2008, 07:31 PM   #8220
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Quote:
Originally posted by PMA
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.

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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Old 18th August 2008, 07:35 PM   #8221
FrankWW is offline FrankWW  Canada
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Hit and run posting:

Not unknown physics but perhaps not enough readily known pyschoacoustics?

Hearing isn't linear either with respect to intensity or frequency.

It probably isn't "linear" with respect to discrimination between noise and musical information. Or noise which tracks musical information.

Question: how far down in the noise floor do you have to bury musical signal before it's not noticeable in some fashion, and at what listening levels?
 
Old 18th August 2008, 08:21 PM   #8222
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myhrrhleine wrote/asked
Quote:
You can hear a difference between 4 and 6 layer PCBs? interesting!
For the record. No. And I did not make that claim.

There is however a real and repeatable difference shown by physical measurement. That difference is shown in RF immunity testing (to EN 61000-6-2:2001 and more specifically , to EN 61000-4-3:2002) and PWR-to-GND plane impedance measurements.
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Old 18th August 2008, 08:38 PM   #8223
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QSerraTico_Tico wrote
Quote:
Hey, just tell me what cap type (ceramic, polyprop, PSS, Teflon or anything) and what value I must use on the opamp supply pins. I am NOT gonna read all that articles again! And maybe also on discrete opamp??
If you do not want to do the homework, then use the default 100nF ceramic (preferably in an SMT package and NPO/COG dielectric). One on each supply pin and as close to each supply pin as possible.

Is this the best? Will it even work? You won't know unless you simulate/measure/listen (pick your religion) the particular instantiation in front of you.

If simulating; you will need to prepare good second order models. And unless you have a good 3-field solver for the pcb structure then this is still only an approximation

If measuring; then find a network analyser, RF signal generator and wideband scope (1GHz minimum bandwidth on all counts) and do some serious work in a shielded environment.

For both of these you will need to do your homework to get results that are meaningful and then some more homework to interpret the results and actually improve yr circuit performance

If listening, ...
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Old 18th August 2008, 08:40 PM   #8224
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Whoops, missed my concluding bit..

It depends on what point you give up and say "this is good enough for me".

But this is the Blowtorch thread and we are supposed to be shooting for Mars (humanity has already got to the moon...)
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Old 18th August 2008, 08:53 PM   #8225
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Scott, do you know what a Shakti Stone or a 'Brilliant Pebble' device actually is? Have you even tried to find out?
These devices DO something. It can be shown that they do, by lab measurement or listening. Why do you 'condemn without examination' devices that you have little or no knowledge of?
What happens is that we push the 'inventors' of the devices away from the engineers, and they just carry on their own, selling 'results' rather than good explanations.
I have conversed with both inventors of these devices, and have been sent samples of their products. I also have tried to understand the nature of these devices and what they tend to do. Both are high frequency energy absorbers. Is this useless in audio? I think not.
It would be like I built and sold a glue-on heat sink for your IC's, and found it to improve sound quality, then to be condemned for selling VooDoo. Have you tried heat sinking your IC's lately? How about increasing the output quiescent current in your AD797? This is what separates the subtle from the ordinary.
 

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