Another way of making the output section with class A predriver - 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 August 2004, 05:44 PM   #1
diyAudio Member
 
JensRasmussen's Avatar
 
Join Date: Jul 2002
Location: Denmark - Jutland
Send a message via ICQ to JensRasmussen Send a message via MSN to JensRasmussen
Default Another way of making the output section with class A predriver

Hello all,

I stumbled across this schematic while looking though some old service manuals. It is the output section of a 150W power amplifier.

Click the image to open in full size.
I like the way itís put together and thought I would share it for interested to use as inspiration for a new design.

\Jens
  Reply With Quote
Old 4th August 2004, 12:33 PM   #2
diyAudio Member
 
destroyer X's Avatar
 
Join Date: Feb 2004
Location: Recife - Brasil Northeast
Default If leach amplifier (pretty yours) already fell down in you foot finger, you can face

The pain of a heavy class A to.... Join us Jens!, you have a lot to help!... came to us.... class A crazy guys.

No matter your intention, this gift is for me.... everyone that open their mouth to talk about class A, i feel as talking directly to me...and i became happy.

Thank you, my wish, thousand guys came here... full of ideas... with courage to expose them.... will be the best thread from long time.

Carlos
__________________
Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
  Reply With Quote
Old 4th August 2004, 01:13 PM   #3
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
I don't see anything special within this topology (apart from looking "very Philips").

Regards

Charles
  Reply With Quote
Old 4th August 2004, 04:09 PM   #4
diyAudio Member
 
JensRasmussen's Avatar
 
Join Date: Jul 2002
Location: Denmark - Jutland
Send a message via ICQ to JensRasmussen Send a message via MSN to JensRasmussen
Charles,

No Philips in here

What else do you see?

\Jens
  Reply With Quote
Old 4th August 2004, 04:39 PM   #5
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
What is device named as IC 1 ?
  Reply With Quote
Old 4th August 2004, 04:45 PM   #6
diyAudio Member
 
JensRasmussen's Avatar
 
Join Date: Jul 2002
Location: Denmark - Jutland
Send a message via ICQ to JensRasmussen Send a message via MSN to JensRasmussen
IC1=MPSA13

Datasheet here

\Jens
  Reply With Quote
Old 4th August 2004, 07:02 PM   #7
Steven is offline Steven  Netherlands
diyAudio Member
 
Steven's Avatar
 
Join Date: Oct 2003
Location: The Netherlands
Indeed, a bit unconventional. Output stage is normal darlington, but bias setting is via resistors R94+95. Temperature compensation via IC1 and TR28, making a temperature dependent current sink. IC1 senses the current through R91. This results in a temperature dependent bias voltage across R94+95.
I don't see the benefit of this compared to a fixed current sink and Vbe multiplier as bias voltage source, though.
Another unusual thing is the driver, TR23, which is an emitter follower instead of the more common common-emitter stage (VAS). This might result in a-symmitrical driving of the output stage. The emitter follower can supply more current (positive edge) than the current sink can sink (negative edge).

Steven
__________________
The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973
  Reply With Quote
Old 4th August 2004, 07:09 PM   #8
jam is offline jam  United States
diyAudio Member
 
jam's Avatar
 
Join Date: May 2001
Location: Auburn, CA, USA
The schematic is probably from a B&O amplifier................my guess is probably the Penta powered loudspeaker.
  Reply With Quote
Old 4th August 2004, 07:21 PM   #9
diyAudio Member
 
JensRasmussen's Avatar
 
Join Date: Jul 2002
Location: Denmark - Jutland
Send a message via ICQ to JensRasmussen Send a message via MSN to JensRasmussen
Hey Jam, you know your vintage stuff

\Jens
  Reply With Quote
Old 4th August 2004, 08:26 PM   #10
sajti is offline sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
Originally posted by Steven
Indeed, a bit unconventional. Output stage is normal darlington, but bias setting is via resistors R94+95. Temperature compensation via IC1 and TR28, making a temperature dependent current sink. IC1 senses the current through R91. This results in a temperature dependent bias voltage across R94+95.
I don't see the benefit of this compared to a fixed current sink and Vbe multiplier as bias voltage source, though.
Another unusual thing is the driver, TR23, which is an emitter follower instead of the more common common-emitter stage (VAS). This might result in a-symmitrical driving of the output stage. The emitter follower can supply more current (positive edge) than the current sink can sink (negative edge).

Steven

Mr. Hood used this type of thermal compensation in some desings. Not so common, but logical...
TR23 is separate the output stage from the VAS. Someone believes, that is reduce the distortion in the output stage, due the low impedance driving.

sajti
  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
making 25w constant class A amp space2000 Solid State 25 1st September 2008 05:07 AM
Output section on preamp questions/breakdown. kegger Tubes / Valves 6 6th December 2006 12:54 AM
Making of Lightforce 1 Class D Powerbriefcase Lars Clausen Class D 66 30th October 2006 11:46 PM
Output section impedance change query KBK Tubes / Valves 7 5th August 2006 01:47 AM
marantz da-12 and cd 7 output section please? lt cdr data Digital Source 1 20th May 2005 11:03 PM


New To Site? Need Help?

All times are GMT. The time now is 09:02 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