Thank you RW for such a comprehensive and easy to read reply. I hope your typing fingers are in 'recovery'
What had prompted me to post was that I've just finished a repair on the original Creek CAS4040. This one was the very first one before the o/p stage was redesigned. This amp was the subject of a long thread on here and David had posted about some compromises in amps design. In particular stability problems with exotic speaker cable. In this case all that was wrong was the volume control and not the output stage thank goodness!!
Thanks also kevinaston1 see post#2 the article is well worth the time taken for a proper read.
Take care out there everyone. Regards, SJM.