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KT150 Tube Matching

Ok. Educate me. I don't know enough to even be dangerous. What are the critical factors used when matching a set of KT150 tubes, say, to go in an Audio Research amp? Transconductance? Bias current draw? A combination of the two? Is there any spec. or threshold on the variations? Does Audio Research do anything special to match their replacement tube sets? 
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Showing 2 responses by knghifi

knghifi
1,668 posts
 
When shopping for power tubes (NOT NOS), I look for dealers with higher quality and larger supply of tubes for a better match. Upscale states they pay extra for tubes with higher micromhos.  ARC is 2x price of Upscale ... don't think you can go wrong with either. 
knghifi
1,668 posts
 
I recently purchased a "matched" quad of KT150 tubes from a well known, seemingly well respected tube vendor. My goal is not to bash him, but to educate myself. One of the "matched" tubes has a transconductance 20% under the average of the other three tubes. When I called to ask about that, I was told transconductance is not a critical factor when matching these tubes for an AR amp. That bias current is the critical factor for tube matching in this particular situation. True? False?
Your question is precisely the reason I always buy power tubes from ARC for maximum performance, reliability and durability.   Call or send an email to ARC.
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