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KT150s in Audio Research Reference 75 (non SE)

Hey all.  Need some advice. 
I've just dropped in KT150s into my Ref 75 (non SE). 

I purchased "perfect pairs" from TheTubeStore.  

I cannot bias them.  They are all too hot.  There are a couple (of the 4) that if I turn the bias pot all they way down will get very close to the bias range (per the needles).  There are another two that even with the pot turned all the way down are reading past the bias range and the needles are about 7mm beyond the bias range. 

Two questions:
1) Am I doing something wrong?
2) Will it hurt anything to run this a little over the ideal bias range, or just shorten the tube life?  Will it impact sound? 

I thought KT150s were drop in for KT120s.  Am I wrong? 

Thanks!

jo1mtb

Showing 1 response by david12

david12
1,454 posts
 

 I find your problem perplexing. A great many people, including me, ran the 150's in the Ref 75 for some time, with no problems. I certainly had no difficulty biasing at all, strange. The only problem was not being able to put the lid back on.

 Having said that, I went on to have the full SE mod, with still more improvement to the sound. I am sure ARC is right, in the long run, you need to have the full SE mod, to avoid problems with the amp.

 Very difficult to be precise, because of the lag time in getting the mod done, but I thought the 150 tubes and the SE mod, provided about 50% each, to the big overall improvement in changing from 75 to 75SE

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