John Curl's Blowtorch preamplifier part II - Page 1809 - 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 19th November 2011, 06:54 AM   #18081
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally Posted by john curl View Post
Don't worry PMA,
I don't. I assume that many are happy with 64kbit/s mp3 and would find it indistinguishable from master tape or 192kHz/24bit in a well controlled, scientific A-B-X test
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 19th November 2011, 07:14 AM   #18082
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
If you would want Bob Pease's article you should Google: 'The best of Bob Pease'. It should be there. I find the article useful.
  Reply With Quote
Old 19th November 2011, 07:23 AM   #18083
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Thanks, I have had the article for several years. Very good, lot of real experience.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 19th November 2011, 07:36 AM   #18084
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
The problem we had with the polyester cap was similar (shape) to the attached simulation, but settling time was longer, in us. The 'overcompensation' or 'undercompensation" was not the case, it was impossible to tune it by R,C values (R//C-R//C) divider. It was fixed with polypropylene caps.
Attached Images
File Type: png capacitor long tail settling.PNG (32.4 KB, 162 views)
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 19th November 2011, 07:55 AM   #18085
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by PMA View Post
The problem we had with the polyester cap was similar (shape) to the attached simulation, but settling time was longer, in us. The 'overcompensation' or 'undercompensation" was not the case, it was impossible to tune it by R,C values (R//C-R//C) divider. It was fixed with polypropylene caps.
That would show up nicely on our bridge null test. An historical point, a professor from SUNY sent a very nasty letter to Ed Dell and in essence he denied the existance of any effect rather that deal with the issue. I think a lot of folks get to this point. I was in the middle, there is an effect and I don't see anything going on that is audible except in the grossest context. The talk of "memory" and "echo" was unfortunate and inaccurate, and I did not want to support it.

The same issue arrises with cap distortion. Folks measure distortion with considerable AC on the cap and extrapolate that to performance where there is no AC on the cap (coupling well past 3dB, bypass).
__________________
Silence is so accurate.
  Reply With Quote
Old 19th November 2011, 08:55 AM   #18086
Bonsai is online now Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
Good points about the AC voltage across the cap Scott. You do need to keep it very low to avoid the distortion.
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/
  Reply With Quote
Old 19th November 2011, 09:03 AM   #18087
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally Posted by scott wurcer View Post
That would show up nicely on our bridge null test.
Probably yes, as the issue we had was more related to frequency dependence of capacitance of the polyester capacitor. For the R//C-R//C voltage divider the DA is not that much an issue (parallel resistor). But is a GREAT issue in the (R-C)-(R-C) divider (series damped capacitive divider). I was building these dividers for HV impulse voltage measurement, and I have been aware of the DA problem since the beginning of the 80-ties.

Regards,
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 19th November 2011, 09:48 AM   #18088
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Variation of capacitance with frequency for several cap types. MKN is polyethylene, and this makes biggest troubles regarding step response. It is impossible to make proper step response compensation with this cap, as the response is both over and under compensated.
Attached Images
File Type: png cap_vs_freq.PNG (41.4 KB, 154 views)
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 19th November 2011, 10:21 AM   #18089
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by PMA View Post
I don't. I assume that many are happy with 64kbit/s mp3 and would find it indistinguishable from master tape or 192kHz/24bit in a well controlled, scientific A-B-X test
Nonsense. Or sloganeering, your choice.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 19th November 2011, 10:40 AM   #18090
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by PMA View Post
MKN is polyethylene
No, it's not. MKN is generally PEN, a type of polyester. Polyethylene is rarely used as a dielectric (despite superb dielectric properties) because of its low melting point.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  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 04:39 PM.


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