vintageHIWATTconvention.com

This is a bit technical, but it shows how much difference there is between 12AX7s made by different manufacturers, and also the variation between different samples of the same tube made by the same manufacturer. Tube manufacturing involves a lot of "hand work" and tubes are not a product of machine precision.

http://www.knzaudio.com/tubeampsecrets/tubetest/

--mark

Sheesh. Talk about trying to hit a moving target !

On the other hand, the data appears to back up the concept that our ears hear different things from different tubes.

Dave