hello bifwynne , no I did not ask ARC , I followed the advice of a university graduated engineer who is doing business in the Netherlands
with his own brand of CD players , amplifiers and other highend products . The 6550 NOS tungsol was installed in 2009 , and is still working . BTW I installed this tube also in my REF 3 SE , I made my REF 3 a home SE version by the capacitor upgrade . All upgrades and mods in my PH 5 ,
REF 3 and CD 7 have made a big improvement , so I did not have to buy new units . I like ARC very much but in my opinion and the Dutch designer the units could be much better by some improvements.