Tubes - How close to be a 'matched' pair?


I'm considering buying some NOS 12AX7s or 12AU7s. How close do the mA ratings have to be to be considered matched? I've seen some 12AX7s with overlapping ranges and the lower limit being within .08 mA of each other. For example: Tube1 .18-.28 mA and Tube2 .26-.34 mA. Does this qualify as a matched pair?
bigamp

Showing 1 response by mechans

A third on the "it won't make an audible difference."
Tube matching is critical with auto bias circuitry on the output tubes.If it really isn't a true automatic biasing circuit but rather a one bias fits all. I avoid manual or fixed bias because thats the kind the end user changes Go Figure