PP Amplifier output impedance matching

[Terry]

Your dad was a good teacher.

Much of the stuff we discuss here was made in the days when 20% tolerance resistors were the norm and all meters were analogue. Parts of the resistance scales of these meters could be very cramped, thus limiting the accuracy with which they could be read.

Fast forward to the 21st Century and someone pops up here or one of the other vintage forums. They are armed with a nice accurate DVM and post something like: "I changed R27 because it had increased in value from 220k to 238k ..."

Of course, it made no difference because it could have been anywhere from 176k and 264k and still have been within tolerance! It probably hasn't changed in value from the day it was manufactured.

I created a chart to illustrate the ranges covered by the various popular tolerances which you might find of interest. I'm sure I've posted it here before but can't find it, so here it is again:



You probably already know this already but the E6, E12 & E24 ranges denote the number of values in each decade.