Hi Mike
All the images I have seen of the internals of the 909 miss out on having heatsinking compound. If you want a second opinion, maybe
ask Rob Flain at Quad, but it is common sense IMO and advised here: http://sound.whsites.net/heatsinks.htm#s9 to aid the transfer of heat
to the external heatsink in every circumstance. If we observe the Quad 405 heatsink bracket it always used heatsink compound. Barry i am sure will
have an opinion on this too.