
Home  Forums  Rules  Articles  diyAudio Store  Gallery  Wiki  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 
29th December 2012, 09:20 AM  #11  
diyAudio Member
Join Date: Feb 2009

Quote:
accordind to your calculation. the First watt F5 will give 6.7W class A at 8ohm.(1.3A bias) acctualy it gives 27W Last edited by AudioSan; 29th December 2012 at 09:26 AM. 

29th December 2012, 09:31 AM  #12 
diyAudio Member

3.6 amps is the bias and is the same thing as the peak current (in class A) and the rms current is 1.414 times lower. Do we talk about the same thing here?
__________________
/PerAnders (my first name) or PA as my friends call me PA03 LM4780 amplifier group buy, SIGN UP HERE for the group buy 69 boards on the list. 37 paid. 
29th December 2012, 09:35 AM  #13 
diyAudio Member
Join Date: Feb 2009

peak current is TWICE the bias

29th December 2012, 09:40 AM  #14 
diyAudio Member
Join Date: Feb 2009

from F5 manual:
For this sort of circuit, a 1.3 amp bias means that the amplifier will operate Class A to 2.6 amps of output current. To understand this, imagine a condition where Q3 and Q4 are idling at 1.3 amps, so that all the current is going from the V+ voltage rail to the V voltage rail, and none is going through the loudspeaker. The power of 2.6 amps into 8 ohms is I^2 * R, or 2.6 * 2.6 * 8 = 54 watts. This is the peak value, and the nature of an undistorted sine wave is that the peak wattage is twice the average, so this circuit would operate 27 watts average Class A into 8 ohms. At currents above 2.6 amps one of the transistors will shut off, leaving the other to continue to increase beyond the 2.6 amps in what is known as Class AB. 
29th December 2012, 09:46 AM  #15 
diyAudio Member
Join Date: Nov 2011
Location: UK

So 1.3A is giving you 27W Class A from the F4.
With the Aleph 4, 2.5A bias gives you a true 100W RMS Class A. Last edited by KatieandDad; 29th December 2012 at 10:00 AM. 
29th December 2012, 09:57 AM  #16 
diyAudio Member
Join Date: Feb 2009

katie. class A power have nothing to do with your rail voltage.
it is, (2.5*2)*(2.5*2)*8/2=100W class A power at 8ohm. 
29th December 2012, 02:22 PM  #17 
diyAudio Member
Join Date: Aug 2012

check this thread how nelson calculates the class A power..
Leaving Class A? Martin Colloms vs Nelson Pass 
29th December 2012, 02:35 PM  #18 
diyAudio Member
Join Date: Feb 2001
Location: USA

I would build it with a tiered power supply.
With a ±20V supply for the low rail the idle would only be 144W, that could be done with only two or three pair of IRFP240/9240.
__________________
Candidates for the Darwin Award should not read this author. 
29th December 2012, 03:11 PM  #19  
diyAudio Member
Join Date: May 2008

Quote:
414w peak is 207w average. 60V is about right for 200W/8ohms. Air forced cooling Mandatory. Last edited by bobodioulasso; 29th December 2012 at 03:20 PM. 

29th December 2012, 07:03 PM  #20 
diyAudio Member
Join Date: Aug 2012

I would be using the IGBT heatsink and each heatsink will have 4 Hexfets dimensions
heatsink width 5 inch length 6 inch depth is also 6 inches... wouldnt that be sufficient? how do I calculate how much each hexfet is dessipating the heat? 
Thread Tools  Search this Thread 


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
200W Class A Power Amp  wengtech  Elektor  7  17th May 2013 07:06 AM 
L20 200w class b amp  ljm_ljm  Solid State  5  3rd October 2011 03:04 PM 
200w class d  WTOAK33  Class D  6  19th July 2011 03:52 AM 
200W in 8 Ohms Class D amp wanted  Session  Class D  5  8th October 2009 07:08 PM 
SE Class A 200W PURE Heat  lineup  Solid State  28  25th November 2008 07:08 PM 
New To Site?  Need Help? 