KT120 back to 6550


Seen a ton of threads praising the KT120 over the 6550 or KT88. I get the new tube's durability and design but given that your amp was originally designed around one of the older tubes has anybody gone back.

I recently purchased and ARC Ref 110 that came with a set of KT120s. The output tubes test and match well so they don't seem to be at the end of their life (same for the signal tubes). 

This was a change from a VT100 equipped with 6550s. The VT100 had good midrange but seemed a little lean otherwise. Percussion was fantastic and voices just right. Just deep bass a little thin. The REF 110 definitely fills in the deep bass but seem a little congested in the midrange. Both top and bottom are an improvement.

Both these amps were sandwiched between an LS25Mk1 and a pair of JBL 4430s. Could be a synergy thing, these speakers work very well with high power solid state (Adcom GFA 5802). I've been trying to work up a good tube amp for these but so far I'm not feeling the love.

So the question is could it just be this system would work better with 6550s instead of KT120s?

Thanks
monoogan

@daveyf  Your observation makes sense.

Regarding:  Was your amp originally designed ( circuit wise) to run 6550's?

I would expect so as the original M120 monoblocks were based on 6550/EL34/KT88 tubes. 

@daveyf  you are talking one point of the whole story.

Which is the design of  amplifier for specific tube.

The other point we need know is about the feature of individual tube.

6550 is better for vocal for sure than kt150.

Kt150 might be good at both end but not middle.

Kt120 is in-between kt88 and kt150.

@runwell  "6550 is better for vocal for sure than KT150"--where do you get that from?? "KT150 might be good at both end but not middle"---Huh???

 

 

 

@daveyf  from my listening and from others experience.

Don't you tell me your idea is from the magazine.

@runwell   No, my idea is from actual listening experience with my own amps and in my system, or with friends amps who are using KT120’s. What amps are you referring to?