Hot Quad 306

Hi,

I've recently moved to a Quad 306 amp (after IIs and 303s) and was
surprised how warm/hot it gets but before I panicked I read the manual
where it warns that it does get quite warm.

Is this true for all Quad current-dumping amps, and if so, why do they
get so hot? The 303 driving a similar setup and at a similar volume
barely gets warm.

Regards,

John.