
Home  Forums  Rules  Articles  The diyAudio Store  Gallery  Blogs  Register  Donations  FAQ  Calendar  Search  Today's Posts  Mark Forums Read  Search 
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 
20th December 2012, 03:24 AM  #1 
diyAudio Member
Join Date: Aug 2012

how much class A power can be expected with a Pair of 2sc5200 1943 pair at +/52V
I would like to bias LM4702 into class A with Bias current of 500mA or may be 1A but will have very large heatsinks measuring 300mm x 200mm and fins will be about 50mm length.
I would like to know that the supply voltage be if its driven in class A. the idea is to put a switch where we can switch the amp in Class A and Class AB but the question is when the amp is delivering about 100W in 8 ohm with 2sc5200 1943 pair then how much it can deliver in class A 20W? 
20th December 2012, 07:58 AM  #2 
diyAudio Moderator R.I.P.
Join Date: Nov 2005

why drive this amp in classA ?
do you think this amp will sound better with higher bias ? (bias adjusting a classAB amp is not like 'the more the merrier') 
20th December 2012, 08:08 AM  #3  
diyAudio Member
Join Date: Mar 2006
Location: Oslo

Quote:


20th December 2012, 08:44 AM  #4 
diyAudio Member

Absolutely right Knuth!
The definition of class A is that the output devices are not turning off during the signal cycle. With 500mA bias, max output peak current in class A is 1A, which is 0.7A RMS (1A * sqrt of 2). Power in 8 ohms is then 0.7^2 * 8 = 4W. The supply voltage is irrelevant as long as it is high enough for the required class A output level. 1A peak in 8 ohms is 8V, so this 4W class A can be delivered with a supply voltage just above +/8V... jan
__________________
An engineer designing a feedback amp is a mixed emotions creature  Hendrik Bode Check out Linear Audio! 
20th December 2012, 10:12 AM  #5 
diyAudio Member
Join Date: May 2008

Without forgetting that disipation is proportional to V supply.

20th December 2012, 11:34 AM  #6 
diyAudio Member
Join Date: Dec 2007

100W in 8 ohm requires a bit more than +/ 40V rails.
If your heatsinks are big enough, then a rough guess is that it should be possible to have a bias current between 1  2 amp. 2 amps of bias current with no input signal, gives a power dissipation of 80 watt in the NPN and 80 watt i the PNP transistor with +/ 40V rails. There might be some problems with derating at high Tcase temps: http://www.st.com/internet/com/TECHN...CD00249630.pdf I assume that you only use one 2SC5200 and one 2SA1943 in your pushpull output stage correct ? Last edited by BachAudioDK; 20th December 2012 at 11:39 AM. 
20th December 2012, 12:14 PM  #7 
diyAudio Member

2A bias gives 4A peak in class A which is 2.8A RMS which is 2.8^2 * 8 = 62W in 8 ohms in class A....
jan
__________________
An engineer designing a feedback amp is a mixed emotions creature  Hendrik Bode Check out Linear Audio! 
20th December 2012, 12:15 PM  #8 
diyAudio Member

Indeed.
__________________
An engineer designing a feedback amp is a mixed emotions creature  Hendrik Bode Check out Linear Audio! 
20th December 2012, 01:56 PM  #9 
diyAudio Member
Join Date: Mar 2006
Location: Oslo

So even if you are using large heatsinks (0.3 K/W), the heatsink temperature would become nearly 80 degrees for a mono 100 W Class A amplifier...

20th December 2012, 02:23 PM  #10 
diyAudio Member
Join Date: May 2008

Anyway, Lme chip doesn't need to run class A for nice sounding .
It will bring nothing but heat. Last edited by bobodioulasso; 20th December 2012 at 02:33 PM. 
Thread Tools  Search this Thread 


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
diyAB "Honey Badger" Class AB Power AmpPair  Helpdesk  The diyAudio Store  2  7th January 2015 05:28 AM 
FS: New boxed pair of B&C ME10 Horns, $15 for the pair!  matevana  Swap Meet  0  17th July 2012 06:02 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 04:18 PM 
Driver transistors for 2SC5200&1943  ttan98  Solid State  43  11th May 2008 02:52 AM 
2sa1302/2sc5200 Power Expected?  zox2003  Solid State  38  27th March 2005 09:57 AM 
New To Site?  Need Help? 