how much class A power can be expected with a Pair of 2sc5200 1943 pair at +/-52V - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 20th December 2012, 02:09 PM   #11
diyAudio Member
Join Date: Apr 2010
Location: Coffs Harbour
I think the OP was looking to compare the classes for his own interest. Without going to high power, Douglas Self's Trimodal amplifier offers A, B, and AB classes at the flick of a switch. A full schematic article and description is carried in his "Audio Power Amplifier Construction Handbook" and "Self on Audio" books, for anyone interested.

This is a worthwhile, finessed project delivering 20-25W/8R in all modes and is more like the full deal for the OP.

Last edited by Ian Finch; 20th December 2012 at 02:18 PM. Reason: add link
  Reply With Quote
Old 20th December 2012, 02:18 PM   #12
jcx is online now jcx  United States
diyAudio Member
Join Date: Feb 2003
Location: ..
for more fun you need the calcs for realistic loads

loudspeakers aren't pure resistors, even "polite" multiway often have |Zmin|< Rnominal/2

then you can adjust power dissipation for phase angle

add reserve for "pumping" resonace, sudenly reversing phase - the current peak can be >5x the Rnominal calc
  Reply With Quote
Old 20th December 2012, 03:32 PM   #13
diyAudio Member
jan.didden's Avatar
Join Date: May 2002
Location: The great city of Turnhout, BE
Blog Entries: 8
Rule of thumb is that the quiescent dissipation for class A is about 4 times the max output power (assuming the power supply voltage is dimensioned for that but not higher).
So that's 400W for 100W class A in 8 ohms.
If you want to keep the temp rise down to say 25 degrees C, which means a heatsink temp of 47 degrees at room temp of 22 C, you need a sink with no more than 25/400 = 0.0625 deg/W.
That will need a lot of (forced) air cooling.

Music is dither to the brain; lets me think below the usual chaos - me
Linear Audio Vol 13 is out! Check out my Autoranger and SilentSwitcher
  Reply With Quote
Old 20th December 2012, 06:07 PM   #14
diyAudio Member
bobodioulasso's Avatar
Join Date: May 2008
ClassA at high power is a terrible waste.
  Reply With Quote
Old 20th December 2012, 07:24 PM   #15
diyAudio Member
Join Date: Dec 2007
If I was to design a 100W into 8ohm class A, I would consider to make it a balanced design. This reduces the rail voltage to half, but off cause doubles the peak current needed. (Amplifiers see 4ohm in BTL)

Rail voltage on output stage can be reduced to a bit above +/- 20volt.
The bias current needed in each Pushpull stage would be 2.5A (20V into 4 ohm=5A or 40V into 8ohm=5A). Power dissipation in each BJT device will be 2.5Ax20V =50W and a total of 200W for the four transistors. (One balanced channel)

I like that both rails of power supply is equally loaded with a balanced BTL output stage.
No nasty rectified signal currents flow in the PSU. This would also be almost hum free, even in a non negative global feedback amplifier. Also the high bias current gives a lower output impedance, compared to a Class AB. But in BTL mode the output imp. is twice compare to one stage.

  Reply With Quote
Old 20th December 2012, 07:53 PM   #16
diyAudio Member
Join Date: Aug 2012
yeah i thought it for a pair of output devices..

LME49811 is said to be built especially for class A amplification more for class A designs..
even if im able to get 30W in 8 ohms is still more than required for my application...

I was going through the site

Gain-X2 - LME49811 15-150Watt Gainclone amplifier

what should be the VA ratings of the transformer to get the 20W of class A power?
  Reply With Quote
Old 20th December 2012, 08:51 PM   #17
diyAudio Member
bobodioulasso's Avatar
Join Date: May 2008
The PSU schematic is silly.
Big resistors into the rails!!!
100mH 6A coils!!!

Edit: This project is a joke.

Last edited by bobodioulasso; 20th December 2012 at 09:02 PM.
  Reply With Quote
Old 21st December 2012, 06:20 AM   #18
diyAudio Member
Join Date: Aug 2012
i know psu is crap but the amplification stage is common. I have a question that can LME49811 can be biased in 2Amps?
  Reply With Quote
Old 21st December 2012, 06:30 AM   #19
diyAudio Member
bobodioulasso's Avatar
Join Date: May 2008
The biasing is all about the output stage.LME itself runs little current.
  Reply With Quote
Old 21st December 2012, 08:54 AM   #20
diyAudio Member
Join Date: Aug 2012
yeah the chip delivers very little current but with one 2sc1517 transistor it gives enough current but the collector current at max is 2A but how to get more current?
  Reply With Quote


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
diyAB "Honey Badger" Class AB Power Amp-Pair Helpdesk The diyAudio Store 4 24th November 2016 12:11 PM
FS: New boxed pair of B&C ME10 Horns, $15 for the pair! matevana Swap Meet 0 17th July 2012 05:02 PM
F/S 1 x pair 3.3uf VCAP OIMP and 1 x pair Mundorf silver/oil 0.68uf qusp Swap Meet 4 31st October 2011 03:18 PM
Driver transistors for 2SC5200&1943 ttan98 Solid State 43 11th May 2008 01:52 AM
2sa1302/2sc5200 Power Expected? zox2003 Solid State 38 27th March 2005 08:57 AM

New To Site? Need Help?

All times are GMT. The time now is 07:38 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2