What is the signal to noise ratio on an amp and is a high ratio better?

Question

if one amp had a snr of 70 and another one had 90 which would b better.. and why

Answer 1

The signal to noise ratio is a measure of how "clean" the sound is, how "pure".  A higher ratio is definitely better, but there has to be a breaking point, where the cost increase is not justified by the increased ratio.  The best way to tell is to go to an audio dealer with a listening booth, and try the different amps for yourself.  Also, in general, a higher wattage amp is better than a lower wattage one, not because you need that extra power, but because you can use more power before you get into the distorted area of the amp's output, the loud end.