Regulated or not regulated?

Hi,

After searching and looking at several threads about power amplifiers, I noticed you guys suggest not to use a regulated power supply when designing a power amplifier (Specially does which are made by ready chips). you told that a common power supply is more enough to be used!
Whats the reason?

Thanx

An amplifier rejects hum and noise on its power supply voltage so voltage regulation is not needed.

Is this true just for monolithic amplifier chips?

Now another question arises, If an OP-AMP or a CMOS/TTL chip is used in away with a Power amplifier (the power amplifier happens to be the last stage) then Does the designer need an regulated power supply for The OP-AMP or the logical chip, or the Power amplifier is enough to remove Distortions due to leakage of a perfect power supply?

An opamp and a power amp reject hum and noise from a power supply so they do not need a regulated supply.
Old TTL logic needs a regulated 5.0V supply.
CD4xxx ordinary Cmos works with a supply from 3.0V to 18V and also does not need a regulated supply.
Newer high speed Cmos (74HCxxx) works with a supply from 2.0V to 6.0V and also does not need a regulated supply.