For several years the original Svetlana 12AX7 tube from St. Petersburg (Winged “C”/SED) tried to develop a good 12AX7 and mostly failed. The current production Svetlana 12AX7 is a New Sensor product and is a member of 12AX7-EH and Tung-Sol 12AX7 family. All three of these tubes is virtually identical. The biggest difference seems to be in plate coating, gain and sound quality.
I find the tube to sound a bit smoother than the EH and it has less gain than the Tung Sol. If you are not inspired by the Electro Harmonix and also find the Tungsol too grainy then this is the tube you want to give a chance. It has everything you want in a good pre-amp. Low noise, no Microphonics issues and very clear and open without being too bright. The construction is on par with the more expensive Tungsol. The price point on this 12AX7 tube is great because it will hold its own with more expensive options. Samples seem very reliable. If you like the JJ ECC83S but want something with a litter more glimmer this is where you should put your money.