[R-390] Resistors

[Flowertime01 at wmconnect.com]

Bernie,

Just like the name says. However it is said with a lot less cheek than when 
talking about some low noise oxygen free audio stuff.

Guys WHAT is a LOW NOISE RESISTOR?

If you are draging .000001 micro amps across 2 ohms a low noise resistor is 
not going to have a lot of value.

If you are draging .1 amps across 1K ohm dropping a 100 volts and spilling 10 
watts of heat into the air, then a low noise resistor may be in order.

Two extreme examples. Good low noise resistors have uses. Just because you 
can do it should you do it? 

All resistors no not have the same noise. Noise is how much variation you get 
in current across a resistor when a constant voltage is applied.

We like to think all resistors are rock solid constant state devices that 
never vary one atom in conduction. Problem is this just is not how it works in 
the real world.

Over ten minutes you get a fair average. Over a second you get a fair 
average. At any instance you can get a good variation that amounts to noise.

So better resistors than the old carbon resistors have been developed and put 
into production.

If you put one into a circuit some where will it make a difference you can 
hear? 
YMMV. depends on where you are putting it. 

>From the extreme examples, it looks like high current circuits would benefit 
most from a low noise resistor.

RF front ends, Oscillator and mixer circuits being the noise determine 
circuits in a receiver would be candidates for low noise resistors.

Some new caps are also lower in noise than some older model caps. The new 
smaller size and lower leakage get more selling points than cap noise. Leakage in 
a cap is not constant. The variation is not large. but variation in leakage 
amounts to change in the circuit. This change is defined as noise. So many caps 
get changed not because they do not hold a charge and perform the filter 
function we expect from them. They get changed because they leak at a not constant 
and varying rate which can be measured as varying noise at the receivers 
output.

Roger AI4NI