[sdiy] Tube Saturation/Distortion, Basics?

[Michael Zacherl]

Hi List,

anyone there who can point me to a ressource 
(preferable in the Web) which explains what 
happens to a signal when put through an tube 
amplifier circuit which is saturated?

Currently I'm exploring my H&K Crunch Master and 
became quite unhappy with it meanwhile - I was 
expecting at least some sort of compression of the 
input signal before getting "squeezed" and mildly 
clipped, rather than hearing sawtooth like 
overtone behaviour (the scope proofs my ears right).

Actually that what I am seeing makes me think that 
  this is on purpose since AFAIK a signal 
distorted by a saturated tube looks rather 
different then this here: 
http://arsprototo.at/sdiy/cx-3/CrunchingKorgCX-3.html#hk_shape

Thanks, Michael.