Class B w/o crossover distortion (1975) - Page 9 - 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 7th February 2010, 10:49 PM   #81
forr is offline forr  France
diyAudio Member
 
forr's Avatar
 
Join Date: Dec 2004
Location: Next door
There is a quite great difference between Hans Hartsuiker's and Peter Blomley's circuits : the common base transistors are driven on their emitter by a low impedance (ouput of the 5534 + 10 Ohm) in the first circuit and by a high impedance (about 20 kOhm) in the second circuit, which then works more like a current source. To me, this last one seems the good way to implement the idea.
  Reply With Quote
Old 9th February 2010, 10:06 AM   #82
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Quote:
Originally Posted by AKSA View Post
Hahfran,



I'd be interested in your attempt.... this has defied some of the best brains on the planet for fifty years.... you may be moving towards error correction feedforward, of course.

However, how about we strike a compromise? A conventional, voltage driven output stage, BUT, with no switching off at the output devices at any time? Would this suffice? It's been done, of course, a gasoline engine doing diesel tricks, and this could avoid a large Class A clunker with its grossly inefficient quiescent current.


Hugh
Zero bias diodes based on zero point energy don't have a pn junction these are not Schottky diodes in fact, theoretically, they should conduct at bias levels in the range of nanoVolts.
However the idea with CMOS audio switch controlled by zero cross detector
to split the signal in the frontend or input doesn't work that will produce more
crossover distortion than a class B....
So what about the compromise ? I think however after reading a translated excerpt of Baxandall's comment on the output triple cascade the idea of current driving has merits over voltage drive since there are now power transistors with a large signal current amplification versus frequency that suffice the requirements. These did not exist in 1969.
  Reply With Quote
Old 9th February 2010, 01:28 PM   #83
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Coming back to the original Visch circuit, it does suffer from pretty nasty dynamic artefacts:

The sim shows what happens when a significant level of signal (15V peak ie. 25% of nominal power) is applied after an idling period: the .ic statement defines the voltage across the hold capacitor, 1.69V when idle.

During the first few cycles, the initial Iq of ~50mA is insufficient, and results in clipping of the negative part of the waveform.
After some tens of ms, the Iq rises to 650mA, and the clipping disappears.
Attached Images
File Type: gif VischP.GIF (35.1 KB, 547 views)
  Reply With Quote
Old 9th February 2010, 02:47 PM   #84
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Certainly this is however a general disadvantage of bootstrap caps. I consider the Bloomley topology -although it is quite far from a typical diy - as superior in this respect. Further the triple cascade features excellent thermal iq stability.
  Reply With Quote
Old 9th February 2010, 03:30 PM   #85
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
This is not a bootstrap: boostrapped amplifier have no problems with sudden transients, quite the contrary. They are unable to pass DC, but the capacitor can be made as large as practical to increase the LF response.
Here, if the capacitor is made larger, it will only increase the response time. And if it's too small, the amplifier will distort. There is no acceptable trade off.
  Reply With Quote
Old 9th February 2010, 03:32 PM   #86
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by AKSA post #80 View Post
Tief, To answer these excellent questions you must build the circuit, subject it to measurement and listening tests over a large sample. And once you have the answers, you may be reluctant to share your findings publicly! These questions precipitate forum wars, with everyone having an opinion, but no one willing to build the prototype.....
Have a great week, Hugh
................ but no one willing to build the prototype. I hope, some guy's will do this in the next time

Last edited by tiefbassuebertr; 9th February 2010 at 03:34 PM.
  Reply With Quote
Old 9th February 2010, 03:54 PM   #87
diyAudio Member
 
Join Date: Jun 2004
Location: the Netherlands
Dear,

Is Arcam not doing the same trick here with their P1 amplifier?

C116/C133 and C117/C134 should prevent early turn off.

With kind regards,
Bas
Attached Images
File Type: png Screen shot 2010-02-09 at 4.52.05 PM.png (98.3 KB, 523 views)
  Reply With Quote
Old 9th February 2010, 03:56 PM   #88
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Quote:
Originally Posted by Elvee View Post
This is not a bootstrap: boostrapped amplifier have no problems with sudden transients, quite the contrary. They are unable to pass DC, but the capacitor can be made as large as practical to increase the LF response.
Here, if the capacitor is made larger, it will only increase the response time. And if it's too small, the amplifier will distort. There is no acceptable trade off.
A bootstrap is always a compromise of two contradicting requirements.
The cap has initially a charge according to C*V. If the transient is negative the cap must be charged and the time constant is proportional to C. Thus the contradicting requirements are according to the polarity of the transient signal relative to idling. Exactly a bootstrap functions perfectly if the amp always idles.
  Reply With Quote
Old 9th February 2010, 06:03 PM   #89
hahfran is offline hahfran  Germany
diyAudio Member
 
Join Date: Dec 2007
Here is another non switching circuit
Attached Images
File Type: jpg nonswitching4.jpg (77.7 KB, 534 views)
  Reply With Quote
Old 9th February 2010, 06:43 PM   #90
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by hahfran View Post
A bootstrap is always a compromise of two contradicting requirements.
It isn't:
In the (crude) example BS1, the amplifier is operated at its maximal power, with a bootstrap capacitor of normal size: the voltage across the cap is centered about 5.4V.
BS1idle shows the no-signal condition: C2 now has a stable 5.4V voltage.
There is no difference, because the circuit is linear: the average potential on <**> and the average potential on out> remain identical, independent of the signal level.
Quote:
The cap has initially a charge according to C*V.
This means that the CV product remains constant, provided the capacitor is large enough.
Quote:
Thus the contradicting requirements are according to the polarity of the transient signal relative to idling. Exactly a bootstrap functions perfectly if the amp always idles.
The only contradicting requirements are that of size vs. performance:
Hicap shows an extreme, with 100 farad capacitance, and locap shows the other extreme, no cap at all.
Ideally, C2 should be replaced by a battery, there would be no LF response issue.
Attached Images
File Type: jpg BS1.jpg (151.9 KB, 483 views)
File Type: jpg BS1idle.jpg (161.0 KB, 404 views)
File Type: jpg BS1HiCap.jpg (164.9 KB, 127 views)
File Type: jpg BS1NoCap.jpg (169.1 KB, 137 views)
  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
low crossover-distortion class AB output stage topologies capslock Solid State 72 10th May 2013 08:48 PM
Exactly titles of old transistor data books from NEC, SONY and Fujitsu (1975 - 1985) tiefbassuebertr Solid State 5 12th December 2011 06:31 PM
Crossover distortion - be gone! Circlotron Solid State 4 24th August 2009 01:09 PM
Crossover distortion lumanauw Solid State 100 14th January 2005 01:58 AM
Crossover Distortion? Killjoy99 Multi-Way 8 30th March 2004 06:10 AM


New To Site? Need Help?

All times are GMT. The time now is 05:30 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