so here is a way to see the problems when you use a constant current source as a supply for an amp output stage.the schematic shows an amp output stage with 30V rails. Q1 and Q4 are the output transistors. Q2, Q3 are the current sources set for 500mA. the input waveform is a 35.35Vrms sine wave (50Vpeak). as can be seen in the second picture, the output is a distorted waveform with 4V peaks (blue=input, green=output). the third picture shows what's going on at the output stage collectors. green is the output waveform, blue is the collector current, which gets limited to 500mA, and the red waveform is the output transistor Vcc, which dips down when the current limiting is active. this circuit would work great if the desired result were soft clipping of the type made by a tube amp. but for a solid state amp for listening to music, the performance of this output stage is horrible.