KT150 Tube Matching

Most Audio Research amps and I am sure others, run the tubes in pairs. There is one driver tube for each pair. While you can check the bias of each tube, you bias the pair with one pot. So you want closely matched pairs of tubes. You don't want to have one tube bias reading really low while the other is high.

 You need to check the bias often when you replace power tubes. The bias will drift as they burn in. You don't want a tube running really hot for a long time. They will settle down as they burn in. This is a lot less of an issue if you get power tubes that were burned in a bit before matching. They won't drift nearly as much.

 I don't know about paying extra for platinum matching and such. I just email Jim McShane. Tell him I need two quads of the power tube I want. I also tell him what amp they are for. His tubes are fairly priced and I have never been disappointed Yet. I have been buying tubes from him for nearly 20 years now.




 

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?

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.