audio Research REF 110 and KT 120 tubes

I just put 2 matched pairs in my VS55 and biased them to 65 and they sound great much better bass. Over all seemed to impart a greater sense of power. I had been using NOS tungsol 6550 and my first impressions are that the KT 120's sound as good in the highs and midrange and much better bass with my dynaudio excite 16 speakers only about 10 hours so far I would think that they need bait more time to break in

Just adding this list to help out anyone who may stumble upon this thread.

Credit for this goes to A'gon member Hifigeek1. He posted this on another thread.

04-19-12: Hifigeek1

The following is a list of ARC amps that are authorized to use the KT-120:

VS55, VSi55, VS60, VSi60, VS110, VS115, REF110, VM220. I hope people find this useful as there seems to be a lot of confusion about it.

@Jedinite24 thank you for the kind words. I neglected to add: REF210 requires field or factory mod. REF610 requires factory mod. May the force be with you!

Can someone help me with my Reference 210 .I understand that it can use KT 120 tubes but no one can tell me what mods I have to do .Asked Audio Research ,they can’t tell me anything but that they don’t have the parts anymore which sounds like a typical Audio Research cop out .I have owned Audio Research products since the1980’s and love them but hate the runaround sometimes from them .Had a service tech there tell me no parts for an Audio Research D-400 and they told the owner there were parts .So they would not sell me the amp and they have listed it for 13 weeks on various platforms and told me it could be fixed .So I don’t know who to trust anymore .First post by the way .Thanks if it’s just a resistor why won’t ARC tell me ?