ARC Ref 6 tube replacement

I replaced in my REF 3 the small tubes by 6H30P-DR super tubes and the one in the powersupply by a NOS Tungsol 6550 blackplate , the are no better replace tubes imho . 

hello tatooedtrackman , I got the suggestion from the tubedepot some time ago for replacement of the blacklabel , they suggest  the SED 6550 black sable . My tube replacement for the REF 3 by the blackplate tungsol gave me the following impression : bass tighter , more refined and more resolution .