[Amps] Price per Watt Conversation

[Catherine James]

Thanks, Jim.  I am learning something new here every day.

I've been clear for some time on the fundamental conflict between good linearity (indirectly creating good IMD) and efficiency. With the last couple of days of discussion added, I now see that there's also a fundamental challenge in getting good efficiency and good thermal handling, and that the negative feedback solution isn't necessarily practical for some designs.

The ideal amp would be highly efficient for lower power draw and minimal need for heat-sinking, have excellent linearity and IMD, use cheap devices, and support ALC, voice compression, and 100% duty cycle modes.  Looks like a square circle. :-)

73,
Cathy
N5WVR

Jim Thomson <jim.thom at telus.net> wrote:
 
 ###  NFB =  Negative feedback.  3 db of NFB means you also reduce the gain 
 of the amp by 3 db.  On paper, to achieve say a 10 db improvement in IMD,  you require 11 db of NFB.
 
 ##  6 db of NFB on a SB-220  means you now require quadruple the drive 
 power.   NFB will work on a SS amp, since the gain is sky high  to begin with.