Class S - 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 17th August 2011, 04:13 PM   #1
gareth is offline gareth  Wales
diyAudio Member
 
gareth's Avatar
 
Join Date: Jan 2008
Question Class S

Could anyone tell me if the Class S (Sandman) type amps are still in use today ? Are they any good ? And is it worth trying to make one ? If I understand correctly they work in a similar way to the Quad current-dumping technique.

I am looking to build my first dual-mono power amplifier. I have always liked the idea of the current dump and was intrigued by the Class S when I was younger. Truthfully I would like to go down the class A route but they are very inefficient, but good on a winters' evening ! I know that a well designed Class B sounds good, that's what I am using at the moment, but would like to know what the general opinion is out there. Am I going down the wrong path ?

Thanks

Gareth
  Reply With Quote
Old 17th August 2011, 04:46 PM   #2
diyAudio Member
 
Join Date: Apr 2011
Location: Pretoria
AFAIK the class S was only/mostly used in low powered amps.

Tandberg Audio made this little 15W (25W according to some sources) amp named "Troll" before they folded their tents. I believe it was class S. It is quite rare today.

Click the image to open in full size.

For building your first amp, it would be best to stick to class B. Less expensive to build and run.

Last edited by ingenieus; 17th August 2011 at 04:52 PM.
  Reply With Quote
Old 17th August 2011, 04:56 PM   #3
gareth is offline gareth  Wales
diyAudio Member
 
gareth's Avatar
 
Join Date: Jan 2008
Quote:
Originally Posted by ingenieus View Post
AFAIK the class S was only used in low powered amps. Tandberg Audio made a 15W (25W according to some sources) one before they folded their tents.

Click the image to open in full size.

For building your first amp, it would be best to stick to class B. Less expensive to build and run.
Are they that bad ? Didn't Technics have a bash, though not for long ? What about the current dumpers ? Any ideas ? Or stick with Class B ? I have read 'Th eHigh Power Audio Amplifier Construction book' by @forgotten the name' sorry, but he is an American I believe. He mentions all the different output transistor/mosfet configurations to be used and there were three to choose from I think. I fancied a common emitter, again if I remember correctly, and the cascode design because of it's high bandwidth, but after reading about all the pro's and con's he mentioned I was a bit confused as to where to go which is why I wanted to go down the class A route (still would actually) and possibly the current dump.

Yours
Slightly confused
  Reply With Quote
Old 17th August 2011, 06:17 PM   #4
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
I think you will find that "Class S" is a trade name for a design, much like
"Class DX", not a category recognized by IEEE.

  Reply With Quote
Old 19th August 2011, 01:15 PM   #5
gareth is offline gareth  Wales
diyAudio Member
 
gareth's Avatar
 
Join Date: Jan 2008
Quote:
Originally Posted by Nelson Pass View Post
I think you will find that "Class S" is a trade name for a design, much like
"Class DX", not a category recognized by IEEE.

Thanks Nelson, I thought wrong then. I thought it was actually a type like A, AB, B, D etc. In your opinion do you think I should go down this route ? Initially I wanted to build class A because of it's topology, transistors/MOSFET's being always on and thus no switching distortion as they are biased on and off. Then, having always liked the QUAD current dump I thought of trying one of those.
There is another reason I fancied a Class A and that is because I have no oscilloscope or acccess to one and I thought it may be easier to set up the Class A because of this. Am I thinking along the right road or should I think elsewhere. I would appreciate your honest answer here as you are the well respected Mr. Pass.
  Reply With Quote
Old 19th August 2011, 04:25 PM   #6
diyAudio Member
 
Join Date: Apr 2011
Location: Pretoria
Class S was was all about efficiency. It is quite similar to Class D. Some say it is exactly the same. Others call it soft switching as opposed to the hard switching of Class D.
  Reply With Quote
Old 19th August 2011, 05:14 PM   #7
Symon is offline Symon  United Kingdom
diyAudio Member
 
Join Date: Mar 2002
Location: Herts, UK
Sandman has published a number of designs, the one I believe is usually termed Class S is similar in topology to the QUAD Current Dumper. But operates on different principles.

Audio and Hi-Fi Handbook - Google Books
page 272

this link shows the basic layout, and it's not in any sense class D
  Reply With Quote
Old 19th August 2011, 08:03 PM   #8
jez is offline jez  United Kingdom
diyAudio Member
 
Join Date: Jan 2004
Location: n.e england
It's nothing like class d! Closest is the current dumping idea from quad.
Dr Sandman sued Technics over his design in the late 90's... Don't know if he won !?
__________________
Repairs and mods to Real Hi-Fi, guitar amps and P.A. in North East England. http://www.arklesselectronics.com
  Reply With Quote
Old 19th August 2011, 08:39 PM   #9
diyAudio Member
 
Join Date: Jul 2003
Location: Bath, UK
Exactly, Dr. Sandman's amp is elegant in a different way - it uses a passive bridge so that a (high power, relatively low-precision) Class B amp drives the majority of the load, and small, ClassA amp provides accuracy via a scaled, complementary output, and the two sum to high accuracy. Another way of looking at it (John Linsley Hood's view I think) is that effectively the big/dumb side drives the output so that the class A side 'see' a very high-impedance load well within its scope. It is not Quad-style 'current-dumping' but a related approach and also elegant.

I believe the principle got appropriated into Technics 'Class AA'
  Reply With Quote
Old 19th August 2011, 10:25 PM   #10
jez is offline jez  United Kingdom
diyAudio Member
 
Join Date: Jan 2004
Location: n.e england
Yep.
It basically uses the small accurate amp to make the larger one "see" a high impedance load (so slightly different from what you described) via the bridge network. If you use even a basic push pull emitter follower output stage with enough bias to get round the crossover region then if you are only driving say 1K rather than 8R the distortion is very low.
Yes it was the class "AA" Technics that ripped off his idea. I hope he won...
__________________
Repairs and mods to Real Hi-Fi, guitar amps and P.A. in North East England. http://www.arklesselectronics.com
  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
Class-AB meets Class-D: Yamaha's EEEngine Topology - where are this Diy Projects? tiefbassuebertr Solid State 29 14th April 2014 05:12 PM
Collection of Class B topologies <100mA Idle and Sound closest by Class A tiefbassuebertr Solid State 37 27th July 2012 09:04 AM
Can a Class AB PP amp be said to be operating in Class A at low signal levels? ray_moth Tubes / Valves 19 23rd January 2009 08:52 PM
How about a round-up of Class A kit power amps, or collectable vintage class A? Brisso57 Solid State 4 14th February 2007 11:30 AM


New To Site? Need Help?

All times are GMT. The time now is 03:59 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