Mixed feedback - diyAudio
Go Back   Home > Forums > Loudspeakers > Planars & Exotics

Planars & Exotics ESL's, planars, and alternative technologies

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 May 2006, 10:52 PM   #1
Bazukaz is offline Bazukaz  Lithuania
diyAudio Member
 
Bazukaz's Avatar
 
Join Date: Nov 2005
Location: Vilnius
Send a message via Skype™ to Bazukaz
Default Mixed feedback

Hi,
Recently i found the following article for improving output tranformer's performance.Maybe it would be useful for ESLs , especially lower quality trannies ?

http://www.lundahl.se/pdfs/papers/feedbck.pdf

Regards,
Lukas.
  Reply With Quote
Old 9th May 2006, 11:58 AM   #2
diyAudio Member
 
Join Date: Dec 2003
Location: Tulips, windmills and wooden shoes.
Looks like a negative resistance to me.

It might not be suitable for driving capacitive loads like esl's.
  Reply With Quote
Old 13th May 2006, 06:20 AM   #3
orjan is offline orjan  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Stockholm
The negativ fedback is only set to be enough to nearly cancel the serial resistans in the primary.
  Reply With Quote
Old 13th May 2006, 08:28 AM   #4
maudio is offline maudio  Netherlands
diyAudio Member
 
Join Date: Apr 2006
Location: Netherlands
Yes, and the winding resistance of the primaire is the least of your worries when designing an ESL-transformer

What makes a good esl transformer so difficult to design is the combination of required output voltage (together with the v/turn ratio determining # of sec turns) and the large frequency range: the low frequency limit requires a large # of prim turns but the high limit requires low internal capacitances and low leak, what in turn requires as little turns as possible. In other words, the problems are at the secundairy side.

I am currently trying to design an amplifier/transformer combination that includes the transformer in the feedback loop. But it proves very difficult to obtain enough bandwidth
  Reply With Quote
Old 13th May 2006, 11:55 PM   #5
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
the point is that you're missing is that cancelling the pri resistive current causes a very large reduction in low frequency distortion

http://www.analog.com/library/analog..._handbook.html

chapter 6 ~ 6.70+

the question is could you usefully rely on this to extend esl transformer usable bandwidth lower limit
  Reply With Quote
Old 14th May 2006, 08:19 AM   #6
maudio is offline maudio  Netherlands
diyAudio Member
 
Join Date: Apr 2006
Location: Netherlands
Quote:
Originally posted by jcx
the question is could you usefully rely on this to extend esl transformer usable bandwidth lower limit
Interesting paper, thanks for the link!

I believe this method could to some extend be useful to lower low frequency distortion by the transfo, if it could be made to work properly in capacitive loads. But than again, I don't believe low frequency distortion is something to worry about. Transformer distortion will be overshadowed by other esl-related problems anyway (resonance, non-uniform membrame motion etc) in the low freq range.

But to answer your question, it will not extend the low frequency limit. The lower bandwidth limit of a practical ESL transformer is not set by distortion problems but by core saturation limits that impose a hard limit on the voltage the transfo can handle at a certain frequency, derating linear with frequency. In addition primairy inductance sets another limit (Zprim must not drop below what the amp can drive @ 20 hz). Whatever comes first sets the limit.
  Reply With Quote
Old 16th May 2006, 06:34 PM   #7
orjan is offline orjan  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Stockholm
Well, the primary inductance is only a small signal aproximation. At large signals, close to core saturation, the value decreases.

And, yes, it works. I used it with line level transformers. It extends the usfull, as in some set distorsion value , low frequncy limit.

With transformers you could do as in quad 63s, use 2 for each esl. Then you can have half the voltage ratio.
  Reply With Quote
Old 16th May 2006, 08:37 PM   #8
maudio is offline maudio  Netherlands
diyAudio Member
 
Join Date: Apr 2006
Location: Netherlands
Quote:
Originally posted by orjan

With transformers you could do as in quad 63s, use 2 for each esl. Then you can have half the voltage ratio.
That's a good way of doing things but the price you pay is lower primaire inductance as both primaire coils are in parallel and they don't share the same magnetic circuit.

Even better solution is therefore to place the two coil-former from those two tranformers on one core, which can be done by using two coil-formers on a double C-core. To my knowledge this is the best way to make an ESL-transformer.
At least I hope so, I am trying it right now
  Reply With Quote
Old 17th May 2006, 07:39 AM   #9
diyAudio Member
 
Join Date: Jan 2005
Location: Berlin
Yes, yes, yes -
and we are all waiting for you, to have grate success -
and tell us all about...
Regards,
Frank
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Mixed signals??? genmin Car Audio 4 12th February 2009 06:58 PM
mixed bias TUBESMAN Tubes / Valves 2 15th January 2009 01:19 AM
Puzzle of 6 mixed up Aleph 2 pyro2006 Pass Labs 8 29th March 2007 09:06 PM


New To Site? Need Help?

All times are GMT. The time now is 06:01 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