John Curl's Blowtorch preamplifier part II - Page 2426 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th July 2012, 08:55 PM   #24251
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by simon7000 View Post
Yes it is calculable. This is for a linear continuous time system, not a sampled system. The question is at what level can this distortion be heard?
The use of imprecise language makes a technical discussion very difficult.
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  Reply With Quote
Old 6th July 2012, 09:12 PM   #24252
1audio is online now 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
With enough R's and C's and a delay line you might be able to accomplish that. Still no new harmonics without a non-linear component. Its just not happening.
__________________
Demian Martin
Product Design Services
  Reply With Quote
Old 6th July 2012, 09:20 PM   #24253
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by scott wurcer View Post
The use of imprecise language makes a technical discussion very difficult.
If you do a test on a "passive" (linear?) part, like a capacitor, and that test produces a second harmonic AND the listener description of the part is the same as hearing a tone or music with added second harmonic.... ??? call it what you want -- I call it distortion. The cause of it is dielectric absorption ..... lower the DA and the same test shows no or much reduced 2nd harmonic. And, again, listeners say it sounds better. What's the problem here?

The only other thing new is that the test did not use a symetrical waveform (sinewave) and was more like transient music signals.... which lead to greater peak levels of distortion (than sine wave analysis) which pointed clearly to DA. Which is what the test was designed to show better than sine wave testing.

As a side note: polar caps were used in ss amps at first and thier model does show a weak diode effect. Contacts and joints of dissimilar metals can also have weak diode effects. But now we design without bipolars and with servo's etc - direct couple. So this is mostly of historical significance.... through listening, insights, and new test methods has lead to better component understanding and better sounding equipment.

Last edited by RNMarsh; 6th July 2012 at 09:40 PM. Reason: extra details - Cap distortion due to DA - testing withOut sinewaves.
  Reply With Quote
Old 6th July 2012, 09:24 PM   #24254
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Real capacitor is non-linear.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 6th July 2012, 09:34 PM   #24255
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by RNMarsh View Post
The cause of it is dielectric absorption ..... lower the DA and the same test shows no or much reduced 2nd harmonic. And, again, listeners say it sounds better. What's the problem here?
The problem is DA is modeled with only a network of ideal R's and C's this can not produce second harmonic distortion. DA and voltage coefficent of capacitance are not the same thing and observing a corellation with one particular dielectric does not make it a general rule.

Dick no offence intended if you're used to a different definition of DA, fine, it's just a misunderstanding.

Demian - Non-minimum phase is impossible with only ideal R's and C's
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  Reply With Quote
Old 6th July 2012, 10:21 PM   #24256
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
That is an 'ignorant' comment about servos, Wavebourn. I will 'prove' it, when I get a chance.
  Reply With Quote
Old 6th July 2012, 10:21 PM   #24257
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by scott wurcer View Post
The problem is DA is modeled with only a network of ideal R's and C's this can not produce second harmonic distortion. DA and voltage coefficent of capacitance are not the same thing and observing a corellation with one particular dielectric does not make it a general rule.

Dick no offence intended if you're used to a different definition of DA, fine, it's just a misunderstanding.

Demian - Non-minimum phase is impossible with only ideal R's and C's
yes thats true. The model you have seen is a simplified model of dielectric behavior - obviously. And, S.W. is correct also, I am sure. And, there is an incomplete explaination of how the DA effect manifests itself audibly. The dielectrics have affects lumped in with DA such that the end result is the rank ordering by DA works for the listener/designer. And, there is some missing info which I have that are not in my notes from the DSP^x talk. The observed results as reported are still useful without getting further into it. Most people - certainly not the place in this blog - are not interested in the gory intellectual details. If you do the test and reread what I did you can figure it out. A more thorough examination could be of some use, i suppose, for completness and full discovery and disclosure..... dont know of any practicle advantage to doing so. Simplify - works for most people.

Does the Volt Coef rank order the same as DA? If so, then maybe THAT is the more correct property to be focused on for choosing caps in audio?


Voltage coeff is part of it, for sure. Especially with ceramics. But the non sinewave test shows higher levels of second for various films as well and listening tests show a direct correlation with DA. Its just more sensitive to this particular issue. What ever it is... if not DA. I would conceed that maybe we need a more complete model. But I am satisfied that the sonic benefits correlate with DA and am practicle about it. Unfinished business for someone else to explain.

Last edited by RNMarsh; 6th July 2012 at 10:47 PM. Reason: futher details
  Reply With Quote
Old 6th July 2012, 10:23 PM   #24258
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Thanks Richard, people think that the MODEL is exactly the REALITY. This is incorrect. The actual DA mechanism could easily produce non-linear distortion as well, even if the MODEL cannot.
  Reply With Quote
Old 6th July 2012, 10:32 PM   #24259
1audio is online now 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
Quote:
Originally Posted by scott wurcer View Post
Demian - Non-minimum phase is impossible with only ideal R's and C's
Maybe I have the definitions screwed up but I think this would be a non-minimum phase network of R's and C's. Please help me if I am misunderstanding something here.
Attached Images
File Type: jpg Phase shift network.JPG (60.0 KB, 147 views)
__________________
Demian Martin
Product Design Services
  Reply With Quote
Old 6th July 2012, 10:49 PM   #24260
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
It could be that volt coeff is the more accuarte indicator rather than DA. If volt coef follows the same ranking as DA then it is best to use that. -RNM
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 12:07 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2