This new production 12AX7 / ECC83 tube is New Sensor's reissue of the famous Mullard 12AX7.
Microphonics is not an issue despite the larger that average plate structure. The transconductance on my sample was the same as two NOS samples I measured. Not really high gain at all, but a real good noise floor and a nice smooth tone that doesn’t encourage ear fatigue the way some preamps can be.
The Mullard name and trademark have been acquired by the New Sensor Corporation. This new production Mullard 12AX7 tube is manufactured at their Xpo-Pul factory (also known as Reflektor) in Saratov, Russia. New Sensor is an American corporation and since taking ownership of this factory has been steadily improving the quality of current production tubes.
One other note about the construction of these tubes is they have filaments that are almost completely encased in the plate structure. They often don't "light up" when working properly. This is not a problem, it's normal for the reissue Mullard 12AX7 / ECC83.