Douglas: thanks for your respones. You are right as I used an incorrect term which is used in connection to amplifiers. I think that the agreed upon minimum that can be expected with respect to interwinding capacitance in a choke of this size (10 H) is about 30pf. I believe that capacitive filtering and snubbers should deal with all the concerns of this high voltage supply. That said the choke may well be doing something and it needs to be investigated. I have a set of 7 H chokes and assorted other parts and plan to compare and listen to the results. Will post what I find. Best regards Moray James.