John Curl's Blowtorch preamplifier part II - Page 1091 - 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 9th March 2011, 09:01 PM   #10901
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally Posted by hitsware View Post
Negating 'idealness' for a moment,
isn't it a fact that the mutual ' inductance '
of the coils of a transformer is the basis
of its operation ?
Yes. The key word being "mutual."

When the coupling is perfect, there is no inductance. Only the reflected impedance of the load.

se
__________________
The Audio Guild
  Reply With Quote
Old 9th March 2011, 09:03 PM   #10902
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally Posted by jneutron View Post
sheesh...I wish my inductance was primary..the 5 gauss line is over 20 feet away.
You'd be well advised to keep your inductance in your pants and well away from any gauss lines.

se
__________________
The Audio Guild
  Reply With Quote
Old 9th March 2011, 09:12 PM   #10903
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
Quote:
Originally Posted by jneutron View Post
When I test coils around high permeability laminated cores, my HP 4284A calls eddy current losses "resistance" I use the Ls-Rs model.

So if those losses are resistive by nature, then the noise generated by the resistive losses of eddies would be a modulated noise. No signal, no noise..

Cheers, John
I don't think so

in the linear model the electrical resistive paths in the core material are always coupled by the mutual inductances - the model is continuous/distributed so a lumped circuit equivalent approximation requires many branches in a "ladder"/mesh? of partial mutual inductances and resistances

the resistances are "real" and have thermal noise which should show up as frequency dependent noise all of the time

the nonlinear core loss mechanisms may quickly dominate as signal level goes up though

Last edited by jcx; 9th March 2011 at 09:19 PM.
  Reply With Quote
Old 9th March 2011, 11:39 PM   #10904
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by jneutron View Post
You really should have asked about the Ls-Rs model, and how an HP 4284A classes eddy losses as a series resistance within the wire, in addition to the reduction of inductance caused by the eddies..

This implies that any current within the wire not only generates noise within the wire, but the slew rate of the current will cause the eddy currents to generate noise as well. A first derivative based amplitude modulation of a noise source..

I wonder how that would show up on a spectrum analyzer..

Cheers, John
As I mentioned earlier I was disagreeing with the use of the word "excess" noise because it is confusing. Active mixers for instance have modulated noise due to the fact that the operating currents in the Gilbert cell are shuffling back and forth. This signal dependent noise has been studied since at least 1962. The 1/f behavior only will show up (simulation with R, L, C) in a distributed model for the system. This is different of course from when one puts a carbon comp resistor as one leg of a bridge. There you extract the excess resistor noise from the excitation by subtraction. Walt Jung and I built a "perfect" pink noise generator based on this and now I can't find a resistor horrible enough to repeat the experiment.

Sounds like time for an experiment with an ultra-pure sine wave and a transformer. BTW I found some good papers from SLAC on magnetic shielding falling apart at nano-Tesla levels, I would love to see some science applied to this issue it is obviously not nonexistant.

EDIT - I might also disagree a little on this, yes eddy currents are a loss but it is not a given that they generate excess noise (coupled back into the system) especially in a fairly pure conductor.
Attached Images
File Type: jpg noii.JPG (34.0 KB, 159 views)
__________________
Silence is so accurate.

Last edited by scott wurcer; 9th March 2011 at 11:49 PM.
  Reply With Quote
Old 9th March 2011, 11:59 PM   #10905
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
I have to agree with jcx in this case "no signal no noise" does not really apply the noise in the system is a signal. At thermal equilibrium the eddy current losses will be accounted for, i.e. if I take a transformer and resitively terminate it at both ends the losses will show up in the resulting input/output terminal measurements.

Which is another way of saying I have not observed a transformer losing the ability to pass a low level signal even to the point of the thermal noise of its terminations.

This also brings back fond memories of the guy down under that wound 300,000 turns of wire on a bundle of rebar and measured the Schumann resonance (pico-Teslas)
__________________
Silence is so accurate.

Last edited by scott wurcer; 10th March 2011 at 12:06 AM.
  Reply With Quote
Old 10th March 2011, 01:52 AM   #10906
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
I know at least one person that has compared several Lundahl MC transformers to the Jensen. On the last High End Audio show in Utrecht Jaap of Hanze Hifi presented 6 different phonostages with different MC transformers. I will call him today and see what he has to say.
  Reply With Quote
Old 10th March 2011, 02:05 AM   #10907
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 99
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by scott wurcer View Post
I might also disagree a little on this, yes eddy currents are a loss but it is not a given that they generate excess noise (coupled back into the system) especially in a fairly pure conductor.
What then of proximity effect? In practice its just like skin effect but in a multiple layer winding such as found in transformers its a significant loss mechanism. Doesn't it contribute noise at higher frequencies by virtue of increasing the resistive losses in the wires? And if it does then its a signal dependent loss.
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  Reply With Quote
Old 10th March 2011, 02:37 AM   #10908
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by abraxalito View Post
What then of proximity effect? In practice its just like skin effect but in a multiple layer winding such as found in transformers its a significant loss mechanism. Doesn't it contribute noise at higher frequencies by virtue of increasing the resistive losses in the wires? And if it does then its a signal dependent loss.
Not the same thing this is all covered by a multi-physics model at equilibrium. The skin effect can produce fractional f effects. They are still continuous with level, the skin effect does not "stop" below a certain level.

If I put say 100nV (or whatever) on a transformer some of the results presented say mu collapses and I get nothing out. Please present evidence of this.
__________________
Silence is so accurate.
  Reply With Quote
Old 10th March 2011, 02:43 AM   #10909
diyAudio Member
 
Join Date: Mar 2002
with an ideal transformer
there is no voltage accross
the secondary without a load ?
  Reply With Quote
Old 10th March 2011, 02:50 AM   #10910
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 99
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by scott wurcer View Post
Not the same thing this is all covered by a multi-physics model at equilibrium. The skin effect can produce fractional f effects. They are still continuous with level, the skin effect does not "stop" below a certain level.
I think here we're arguing at crossed purposes. I'm not of the view there's anything discontinuous going on. Just offering support for Mr. Neutron's thesis which you seemed to be disagreeing with.

Quote:
If I put say 100nV (or whatever) on a transformer some of the results presented say mu collapses and I get nothing out. Please present evidence of this.
I'd be as skeptical as you of such 'results'
__________________
It doesn't have to take the form of a conspiracy, rather a consensus... James H Kunstler
  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 04:52 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