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Questions on KT150 vs KT120

I’ve been using kt120’s on a VAC, CJ and Audio Hungary for a long time but thought I would give the 150’s a shot on the Audio Hungary. I’m not really enjoying the 150’s like I had hoped. I’ve found they are very dependent on signal tubes, running old Mullard’s to tame it down still not as musical as 120’s, very hifi. Anyone found this to be the case for you. Is it true it needs over 300 hrs to settle down.

paulcreed
daytrader
195 posts
 

I preferred the upgrade to 150s over 88s that came standard with my Amps.  As I recall it was a short breakin period, maybe  a 100 hrs on my QS V4 monos to open up the high frequency that’s about it.  Signal tubes were whatever NOS RCA or Sylvania it came with. Not sure how the new stuff would sound?  So I purchased an extra set inputs when I got the amps many years ago, they do last almost forever unlike the new stuff. Thanks to Mike Sanders stock piling for his customers.

peter_s
1,440 posts
 

I have VAC Phi 200s… Which were designed around KT 88. Kevin from VAC tells me that I could run KT 150s on them, but he doesn’t prefer them. I have not tried yet. Are you running KT 150s on your VAC? Which VAC amplifier do you have?

decooney
2,565 posts
 

@paulcreed for whatever reason and comparing to my local audio shop friend’s same amps, driving back and forth several times to compare, I found his same amps with KT150s were notably smoother and more musical than mine brand new when I got them. With my brand new KT150s I noticed slight changes at 100-150hrs, and he kept telling me "nope" try again at 250-300hrs and see if they smooth out and sound better, and they did at 300hrs.  I’ve sinced boxed them up and went back to KT120s again, yet I do like both sets and the KT150s can sound good with the right front end tubes in the preamp and with the amps too. It can be a balancing act.  

FYI, what I did finally realize with others, some amplifiers are NOT actually designed to run KT150s properly, with insufficient plate voltage.  My amps are designed to run KT50s, KT120s, and I cannot run KT88s as the plate voltage is too high and will burn them up prematurely. 

 

Ask your amp mfg what the plate voltage is on the amps to see if they are actually optimized to run KT150s or not.  Many tend to ignore this because they will plug in and play, maybe not properly though, fwiw, worth asking your amp designers.  

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