Was looking through the manual for the Quad valve pre (QC24 ?) and there was a bit about matching with a power amp with high-ish input impedance - 40kohms from memory. The impedance of the Quad 909 is 20 kohms yet I gather there are people using the two together quite happily. Having just acquired a 909 and looking at the possibility of finding a valve pre to use with it could someone enlighten me as to what I should be mindful of in this respect? Thanks