Double triode 6N1P-EV (6H1П-EB) is a version of 6N1P tube with improved reliability and long service life (more than 5000 hours). It is direct replacement for chinese 6N1 and also offers a better performance. It may be also used as a replacement for ECC88/6DJ8/6922 tubes. But you have to be careful, because there are some important differences. The 6N1P-EB's are drawing considerably more heater current: about 600 mA, comparing to the ECC88/6922/6DJ8 tubes, where it is about 365 mA. In some cases, direct replacement without any discussion with the manufacturer, may end up with damaging of your equipment. Please discuss this with the manufacturer of the equipment. Tubes were produced in the mid 70's. New old stock tubes.