Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Bob Cordell Interview: Error Correction
Bob Cordell Interview: Error Correction
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 8th December 2006, 09:57 PM   #1421
ingrast is offline ingrast  Uruguay
diyAudio Member
 
Join Date: Sep 2004
Location: Montevideo
Quote:
Originally posted by gootee


.... I'm sorry to have brought it up without first doing some research.

.....

- Tom Gootee

Nobody can possibly be aware about everything that is going on, this is a splendid clearinhouse in this respect.

Rodolfo
  Reply With Quote
Old 8th December 2006, 10:30 PM   #1422
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Quote:
Originally posted by mikeks
Reducing K4 from 50 to unity (with the same misalignment of 10% in the gain of summer S1) causes THD to increase by a significant amount, to 0.17%.

Thus, although the magnitude of K4 has no effect at balance, when such an imbalance exists, then it desirable that K4 be made as large as possible to desensitize the loop to the error.

Indeed, increasing the gain of K4 to 1K reduced THD (with a misalignment of 10% in the gain of summer S1) to just 0.00035%.

These results seem to confirm Hawksford's findings, and, on this basis, the circuit modification above is recommended.

Nevertheless, whether these results are replicated in practice remains to be seen.

Discuss.


Mikeks,

I appreciate all of the work that you've done, on this. I have been trying to follow this part of the discussion, even though my knowledge of control theory and mathematics is a bit rusty. But, mainly, I have found it to be difficult to re-navigate the thread, well-enough, due to the number of messages involved, and also all of the links to previous posts, intervening and conflicting posts, corrections, repetitions, et al.

I don't like to be a bother. But, do you already have, or can you provide, a summary, or a single document, or, maybe easiest, a properly-sequenced list of links, that includes all of the really-relevant stuff, so far, "all in one place"? That would also make it much more accessible for everyone who tunes-in later.

If that's not practical or desirable, from your point of view, please feel free to just forget that I asked.

Thanks.

- Tom Gootee
  Reply With Quote
Old 8th December 2006, 10:42 PM   #1423
mikeks is offline mikeks  United Kingdom
Account Disabled
 
Join Date: Jun 2004
Location: Animal farm
Quote:
Originally posted by Bob Cordell



Actually Tom, I've already built a test instrument similar to what you describe. It is called the Distortion Magnifier. I first used it to test my MOSFET power amplifier over 20 years ago. I described the technique briefly in my MOSFET amplifier AES paper.

A more up to date and detailed description of the Distortion Magnifier is provided on my website at www.cordellaudio.com. Just look under "Distortion & Distortion Measurement", then click on "Sensitive Distortion Measurement". I soon hope to have an even more detailed description of the DM on my site.

Cheers,
Bob
Howdy Bob,

Thanks for those pictures of the RMAF. I look foward to attending next year.

Do you have or intend to have any audio products for sale on-line?

Cheers.

Mike.
  Reply With Quote
Old 8th December 2006, 10:47 PM   #1424
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Quote:
Originally posted by ingrast



Nobody can possibly be aware about everything that is going on, this is a splendid clearinhouse in this respect.

Rodolfo

Rodolfo,

You are right! But I also appreciate your kindness for having mentioned it.

- Tom Gootee
  Reply With Quote
Old 8th December 2006, 11:00 PM   #1425
mikeks is offline mikeks  United Kingdom
Account Disabled
 
Join Date: Jun 2004
Location: Animal farm
Quote:
Originally posted by gootee
.......can you provide, a summary, or a single document....
- Tom Gootee
I'll probably get around to doing this, though not immediately.

I've gone to great lengths to link each post to a preceding one in the interest of continuity; navigating your way through these links can't be that difficult, surely.
  Reply With Quote
Old 8th December 2006, 11:21 PM   #1426
powerbecker is offline powerbecker  Germany
diyAudio Member
 
Join Date: Dec 2004
Location: Berlin
Quote:
Originally posted by gootee



Heinz,

Thanks!

I could not resist trying to make it better:

To get a fast step response with no overshoot or ripple, and the same with 1 uF in parallel with the 8 Ohm load, I had to "cheat" and add a NFB loop (AC-coupled!).

Now, there is NO overshoot or ripple in the step response into 8 Ohms. And it's still _almost_ as good with 1 uF added (w/ESR .02). [Steps: 20v p-p output, from 1v p-p pulse input with 2.5 us edge times.]

It can be made more stable with >= 2 uF by increasing C22 to 560 pF or more, at the expense of a slight degradation of the step response when 1 uF or 1 pF is paralleled with the load. The THD-20 can be made lower, also, but probably only at the expense of the quality of the step responses, AFAIK (as far as I know).

THD is .000230%, for about 20v p-p into 8 Ohms (.000229% w/1uF). (Output amplitude was adjusted by changing input amplitude, to match the output amplitude of your ec_amp-hb2.asc circuit, for comparison.)

The EC-Amp-tg3.asc LT-Spice circuit is attached. Remove the ".txt" from the filename.

The circuit is a little troublesome, sometimes, for me, with LT-Spice, especially when using the pulse input. I would like to try, for example, lowering the resistances near the end of the ec loop (R26, R19, R20), or raise R30 to increase the ec loop's gain, but always get a "timestep too small" message from LT-Spice. Similarly, I cannot even lower the pulse input's amplitude without getting an "iteration limit reached" message, which I also get when trying to run an AC Analysis.

- Tom Gootee
Tom,

now I cannot improve it!
Thank you for your excellent work!

Regards
Heinz!
  Reply With Quote
Old 9th December 2006, 12:03 AM   #1427
powerbecker is offline powerbecker  Germany
diyAudio Member
 
Join Date: Dec 2004
Location: Berlin
Quote:
Originally posted by janneman



Well, in electronics like in real life, brute force often has the edge . But playing with ec is quite interesting. Notwithstanding the discussions here that it is equivalent to nfb, the character, if I can call it that, of an ec amp is definitely different from a nfb amp.

You really have to think differently, there is no longer the overriding concern to get very high gain. What strikes me is the almost complete adsense of oscillatory tendencies, ec circuits (at least in my experience) tend to be very docile.

If you are looking to something different from the tired old ways, ec amps are worth a try!

Jan Didden
Jan, there are many ways to Rome....I look always for the shortest (corresponding to my knowledge)
Till today I have never seen EC design which beats NFB.
The proof of the pudding can be, to improve a classD stage with itīs "nice" filter at the end. Here end the way for NFB....
I dontīt try it till now and Iīm not all too optimistic.
For the same purpose I did some simulations with feedforward EC.
This works quite good but it ends always with a far to big correction amp... at that time I also missed a good idea!

Regards
Heinz!
  Reply With Quote
Old 9th December 2006, 07:13 AM   #1428
jan.didden is offline jan.didden  Europe
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: The great city of Turnhout, BE
Quote:
Originally posted by mikeks
Thanks for those pictures of the RMAF. I look foward to attending next year.Mike.

Me 2!

Jan Didden
__________________
Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.
  Reply With Quote
Old 9th December 2006, 07:16 AM   #1429
jan.didden is offline jan.didden  Europe
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: The great city of Turnhout, BE
Quote:
Originally posted by mikeks


I'll probably get around to doing this, though not immediately.

I've gone to great lengths to link each post to a preceding one in the interest of continuity; navigating your way through these links can't be that difficult, surely.

Mike, indeed, your efforts to keep your posts consistent and the story continuous are great. Still a single document would be even greater - whenever you get the time!

Jan
__________________
Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.
  Reply With Quote
Old 9th December 2006, 09:23 AM   #1430
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Quote:
Originally posted by powerbecker


Tom,

now I cannot improve it!
Thank you for your excellent work!

Regards
Heinz!
Heinz!,

Thanks so much for the encouraging words!

You are probably being way too kind. And I probably just got lucky, accidentally. But still, it's always great to hear some praise, especially since I have only been dabbling in electronic design for the last several years, and only seriously for the last two years, after doing no EE work at all for about 15 years, and knowing mostly only control theory and not too much about actual circuits, before that.

Thanks again! Back to the circuits...!

- Tom Gootee
  Reply With Quote

Reply


Bob Cordell Interview: Error CorrectionHide 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

Forum Jump


New To Site? Need Help?

All times are GMT. The time now is 11:43 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki