Bob Cordell Interview: Error Correction - Page 395 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 3rd November 2011, 02:40 AM   #3941
PHEONIX is offline PHEONIX  Australia
diyAudio Member
 
Join Date: Jul 2004
Location: Australia
Default Schematic and models

Hello MagicBox

Here are the models and schematic of Bobs amp , 10 harmonics is the go.

Regards
Arthur
Attached Images
File Type: png Bobs amp.png (82.1 KB, 216 views)
Attached Files
File Type: txt Cordell Models_12_07_2010.txt (11.4 KB, 17 views)
  Reply With Quote
Old 3rd November 2011, 05:58 PM   #3942
diyAudio Member
 
Join Date: Sep 2011
Thanks,

I've just added the required models to the database. Now to do some schematic entry. I'll keep you posted.
__________________
Negative Feedback: The Need for Speed
  Reply With Quote
Old 3rd November 2011, 06:58 PM   #3943
diyAudio Member
 
Join Date: Sep 2011
No more edit button so I'll have to bump. Here are the magnitude results:
Code:
Fourier analysis for $out:
DC component: 3.89269e-005
  No. Harmonics: 10, THD: 0.00322448 %, Gridsize: 256, Interpolation Degree: 1
Harmonic Frequency    Magnitude    Phase        Norm. Mag    Norm. Phase 
-------- ---------    ---------    -----        ---------    ----------- 
 1       1000         19.968       -0.13168     1            0           
 2       2000         0.000402738  -69.532      2.01691e-005 -69.4       
 3       3000         0.000102638  -31.082      5.14011e-006 -30.95      
 4       4000         0.000175408  150.85       8.78446e-006 150.982     
 5       5000         3.0785e-005  -30.074      1.54171e-006 -29.942     
 6       6000         0.000209934  113.57       1.05135e-005 113.702     
 7       7000         0.000299694  44.1631      1.50087e-005 44.2948     
 8       8000         0.000184869  57.811       9.25824e-006 57.9427     
 9       9000         8.66966e-005 -0.68835     4.34177e-006 -0.55668    
 10      10000        0.000185828  -98.169      9.30629e-006 -98.037
You'll also find an image of the schematic in action I also found that this particular schematic behaves a bit erratically. When using the interactive simulation mode (picture 2) and letting it run, the THD would alternate between 0.002 and 0.003, predominantly being 0.003, regardless of timestep resolution.
Attached Images
File Type: png FFT1K.png (38.9 KB, 196 views)
File Type: png CordellTHD.png (39.5 KB, 175 views)
__________________
Negative Feedback: The Need for Speed

Last edited by MagicBox; 3rd November 2011 at 07:11 PM.
  Reply With Quote
Old 4th November 2011, 04:17 AM   #3944
PHEONIX is offline PHEONIX  Australia
diyAudio Member
 
Join Date: Jul 2004
Location: Australia
Hello MagicBox

looks like your results align with the other simulators namely MC9 , LTspice, Pspice and Simetrix. From this it is fair to say that using the same models and circuit all of the above simulators should give similar THD simulations there are no huge differences.

Arthur
  Reply With Quote
Old 4th November 2011, 06:40 AM   #3945
diyAudio Member
 
Join Date: Sep 2011
Yeah, I kept in line with 4ms - 8ms window, 4 periods. However, when I move around the window the THD varies, sometimes few more ppm, sometimes less. On average I'd say it's pretty close to the 0.0027 specified in the schematic. A shame the interactive meter doesn't show more digits, only 3 after the decimal point.
__________________
Negative Feedback: The Need for Speed
  Reply With Quote
Old 4th November 2011, 08:56 AM   #3946
diyAudio Member
 
Edmond Stuart's Avatar
 
Join Date: Nov 2003
Location: Amsterdam
Quote:
Originally Posted by MagicBox View Post
..................
On average I'd say it's pretty close to the 0.0027 specified in the schematic. A shame the interactive meter doesn't show more digits, only 3 after the decimal point.
Hi MagicBox,

Thanks for the sim. But what value we should add to the score list?
I'm reluctant to say 'between 0.002% - 0.003%' and prefer a more accurate figure, i.e. one more digit.
What about this (if you don't mind): repeat the sim with Vin=0.1V and R3=199k. Now you should get 0.026% (that's what MC says).
Divided by ten gives a reasonable estimate of the real value (from the original amp).
If no objections, we could add this value to the list (with the remark 'estimated').

Cheers,
E.
__________________
Een volk dat voor tirannen zwicht, zal meer dan lijf en
goed verliezen dan dooft het licht…(H.M. van Randwijk)
  Reply With Quote
Old 4th November 2011, 07:10 PM   #3947
Account disabled at member's request
 
Join Date: Oct 2008
Hi Edmond

YGM, a bit different matter, but related.

Cheers

Stein
  Reply With Quote
Old 4th November 2011, 07:31 PM   #3948
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by Edmond Stuart View Post
Hi MagicBox,

Thanks for the sim. But what value we should add to the score list?
I'm reluctant to say 'between 0.002% - 0.003%' and prefer a more accurate figure, i.e. one more digit.
What about this (if you don't mind): repeat the sim with Vin=0.1V and R3=199k. Now you should get 0.026% (that's what MC says).
Divided by ten gives a reasonable estimate of the real value (from the original amp).
If no objections, we could add this value to the list (with the remark 'estimated').

Cheers,
E.
No problem, tomorrow I can update the results with your suggestion. Irregardless going by rounding and the erratic behaviour I'm pretty positive that the average sits somewhere around .0027 given the fluctuations and timespans of the 2 readings.

20KHz THD btw was around 0.500% if I remember correctly
__________________
Negative Feedback: The Need for Speed

Last edited by MagicBox; 4th November 2011 at 07:43 PM.
  Reply With Quote
Old 5th November 2011, 07:37 PM   #3949
diyAudio Member
 
Join Date: Sep 2011
Okay, with a 10 times lower input magnitude and increased gain I get ~0.026,
__________________
Negative Feedback: The Need for Speed
  Reply With Quote
Old 6th November 2011, 01:16 AM   #3950
Account disabled at member's request
 
Join Date: Oct 2008
I think we can conclude that the different simulation platforms are giving the same results when we are using perfect models and optimistic models (Cordell models).
It would be interesting if the same guys could run the same simulation using the factory models that I used. (Bob amp models)
Arthur has done it and he did get exactly the same results that I got, so we are missing LTspice, Multisim and MC.

An even more interesting thing to look at would be if someone could build the mentioned circuit and measure it.

A quick note about models;
What is a better model? Is that a model that gives lower THD, or is it a model that is more realistic?
I have made plots of some of the Cordell models and compared them with factory models.

What do you think? (Hint: Jim Early)


BTW: I’m working on a new amp design, in my opinion it’s a lot more interesting to look at ways to lower distortion by designing new circuits instead of tweaking models.
This is what I’m getting when I'm using factory models. The phase margin is very good and there is no sign of oscillation. The circuit isn’t 100% optimised yet, so the final design will have lower distortion (in the simulator).

1K Full power:
Waveform Values
===============
F THD(HARM(V(LOAD))) IHD(HARM(V(LOAD)))
(Hz) (%) (%)
NA NA NA
1.000K 0.000 0.000
2.000K 4.516u 4.516u
3.000K 8.114u 6.742u
4.000K 8.120u 307.598n
5.000K 8.146u 642.329n
6.000K 8.146u 102.139n
7.000K 8.155u 375.882n
8.000K 8.155u 70.221n
9.000K 8.158u 206.201n
10.000K 8.158u 24.095n


20k Full power:
Waveform Values
===============
F THD(HARM(V(LOAD))) IHD(HARM(V(LOAD)))
(Hz) (%) (%)
NA NA NA
20.000K 0.000 0.000
40.000K 7.333u 7.333u
60.000K 25.364u 24.281u
80.000K 26.317u 7.018u
100.000K 26.416u 2.288u
120.000K 26.646u 3.493u
140.000K 28.717u 10.707u
160.000K 28.857u 2.835u
180.000K 29.942u 7.990u
200.000K 29.971u 1.306u
Attached Images
File Type: jpg Model-comparsion.jpg (96.7 KB, 111 views)
Attached Files
File Type: txt Bob amp models.txt (4.2 KB, 16 views)

Last edited by stinius; 6th November 2011 at 01:18 AM.
  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 12:56 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