John Curl's Blowtorch preamplifier part II - Page 3295 - 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 January 2013, 07:12 AM   #32941
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by john curl View Post
SACD's or better, for me. '-)
Jan, just got Vol. 3, thanks.
Good! I am all for 'education permanente' as the French say

jan
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!
  Reply With Quote
Old 19th January 2013, 07:17 AM   #32942
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by stinius View Post
Gentlemen please remember that the measurements shown by JC are made ​​by Samuel Groner / Weiss.
For those interested that haven't seen the measurements, go to Samuel's homepage and download the (op_amp distortion.pdf), (too large to attach)

IMHO Samuel is trying as much as possible to kill all IC OpAmps, why?

Remember that he is working for WEISS and that they have a their own solution. Their own discrete OpAmp.

Think about it.

Stein
Stein, funny you say this. If you are so concerned about conflict of interest, you should start to delete ALL posts in this forum by people who are in the industry. Sorry JC, sorry Scott, Richard, bear - you all have double agenda's can't have that, all your posts pooof...

jan
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!
  Reply With Quote
Old 19th January 2013, 09:22 AM   #32943
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by RNMarsh View Post
Give up guys.... you've tried for months and years to get JC to compare distortion numbers and means and methods... he isnt going to do it. IMO comparing thd and noise and bandwidth becomes a numbers game for marketing. JC has said he belivevs there is more to better audio performance than only those numbers.
The problem is that John explicitly said that competitive preamps using IC opamps were "mid-fi" because of higher 7th and 9th harmonic levels compared to the equipment that his "team" designs. That is an objective, numbers-based claim.

Maybe it's just me and my silly stiff-necked sense of honesty, but if I claimed a performance shortfall for products which competed with mine, I'd have data to back it up or be willing to retract my claim. The fashion audio world is apparently different...
__________________
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 January 2013, 09:44 AM   #32944
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by john curl View Post
For everyone to more completely understand:
Analog magnetic tape IDEALLY doubles in distortion for every 3dB rise in level. Of course, it decreases in the same amount for every 3dB fall in level.
This follows the mathematical law of generating 3'rd harmonic distortion.
So: 6dB rise gives 4 times more, 10dB rise gives 10 times more.
With high speed tape, it is VERY consistent with this prediction.
That's fine, but what evidence do you have that this is applicable to preamps?

If arguendo we use your calculational method to look at a 797 in the distortion magnification mode used by SG (which is unreasonable), for the same signal levels you asserted for the BT (which I agree are reasonable and are 20dB below SG's level), and a 600R load (which is unreasonable), the 7th harmonic would be at (-113dB - 6{20dB}) = -233dB. I think even Ed would strain at that one.

Your assertion continues to ring false.
__________________
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 January 2013, 09:50 AM   #32945
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Quote:
Originally Posted by SY View Post
T

If arguendo we use your calculational method to look at a 797 in the distortion magnification mode used by SG (which is unreasonable), for the same signal levels you asserted for the BT (which I agree are reasonable and are 20dB below SG's level), and a 600R load (which is unreasonable), the 7th harmonic would be at (-113dB - 6{20dB}) = -233dB. I think even Ed would strain at that one.
Even if it was only -500dB, the 7th is an Evil!!
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 19th January 2013, 11:54 AM   #32946
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by john curl
First of all: ANY open loop system that is also Class A has a predictable distortion curve, ONCE you get an accurate set of measurements at some typical level. You can go both up or down in level and PREDICT the distortion with a great degree of accuracy.
Come on everybody, look it up in a textbook on non-linear circuit analysis.
Let me give an example of how I would (and do) estimate distortion in an open loop, Class A system:
First, I get a set of exact measurements of each harmonic at some part of the operating level within the design parameters of the design, i.e. NO pre-clipping levels, as this will throw off the estimate.
Then: For 2'nd harmonic, estimate that its value drops directly with voltage level.
For 3'rd harmonic, estimate that its value drops directly with the SQUARE of the voltage level.
For 4'th harmonic, estimate that it drops to the CUBE of the voltage level.
Etc, etc.
Now what about 7th harmonic? It should drop as the 6th power, which implies that if you drop the voltage level in 1/2, then the 7th harmonic should drop by a factor of 64.
Almost true, John. However, it is not enough to be below clipping - you also need to be below the level where, say, 7th order nonlinearity contributes significantly to 3rd order distortion. Therefore you need a set of measurements at different signal levels which demonstrate that this is true. Provided your set of measurements roughly follow the power law you describe, then you can fairly reliably extrapolate downwards.

There also has to be an assumption that there are no low-level effects in contacts etc. No point in having Class A devices with Class B wiring! Except under fault conditions I doubt that such things are a problem, but some people worry about them.
  Reply With Quote
Old 19th January 2013, 11:58 AM   #32947
diyAudio Member
 
Join Date: Jan 2007
Quote:
Originally Posted by PMA View Post
Even if it was only -500dB, the 7th is an Evil!!
For some its the 7th, for others its Class D amps. Everyone has his phobias I guess.

...usually defined as a persistent fear of an object or situation in which the sufferer commits to great lengths in avoiding, typically disproportional to the actual danger posed, often being recognized as irrational.
Phobia - Wikipedia, the free encyclopedia
__________________
"You have a hierarchy: a mathematician, a physicist (which is a failed mathematician), and an engineer (which is a failed physicist)." - Andrew Jones

Last edited by TheShaman; 19th January 2013 at 12:04 PM.
  Reply With Quote
Old 19th January 2013, 12:45 PM   #32948
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by john curl View Post
I was exposed to it for many years with analog tape recording, in which the 3'rd harmonic (totally dominant because of the tape itself) could be reliably predicted, over and over, with different recording levels, once a single distortion with level was measured.
I am VERY surprised to read that under your pen John. When we arrive near the saturation of the tape, the response curve begin to change. ~0dB is the max level you can achieve at 10hHz and 15 Ips, right ? While you have more than 10dB more available under. So the harmonic distortion is not linear at all, and the higher harmonics decrease, there, where the level increase.
It explain the "hot" sound with tape on hight transients.
I used sometimes, to clip the kick drum, and record-it that way on tape at VERY high level: Tape's saturation removed all the high harmonics, and gave a very natural 'kick' attack, even when the original sound was dull and just resonant with not enough transient. You were not able to hear distortion, just what you believe is the hit of the beater on the skin, while the sound from the desk was awfully saturated.
Quote:
Originally Posted by a.wayne View Post
Very little between 15 and 30 ips ....
Reason why 15 Ips was chosen as the standart professional speed for tape recording.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein

Last edited by Esperado; 19th January 2013 at 12:52 PM.
  Reply With Quote
Old 19th January 2013, 12:55 PM   #32949
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
First, let's address 7th harmonic. Here is a small article on the subject. I didn't invent the problem, just noted it. It took me less than 5 minutes to find it with 'Google'.
Attached Images
File Type: jpg 7th-1.jpg (520.1 KB, 132 views)
File Type: jpg 7th-2.jpg (328.6 KB, 129 views)
  Reply With Quote
Old 19th January 2013, 01:03 PM   #32950
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by PMA View Post
Even if it was only -500dB, the 7th is an Evil!!
Because dominant 7th chord was named "diabolus in musica" ?
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  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 05:33 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