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 hotsauce

No, to me thats not matched, but it shouldn't make a difference. But if you realy do need matched tubes they should be tested at the same operating point as in your amp, and with the same load impedance.

Even if you had tubes that matched perfectly, the in phase and out phase of the phase inverter won't perfectly match.

John C.