AD1/350 was the Telefunken designation for their higher quality version of AD1, capable to replace any AD1, at classic 250V working point, but also it may be operated up to 350V, in order to bring the tube in a range with better efficiency and additional output power resulting from it, yet without increasing dissipation. This higher working point, with historic versions, it will initially work, but the tubes may develop grid current unexpectedly.
EML AD1/350 however is fully free of grid current at any operation point, also at high use hours as well.
Though it is electrically not identical, any existing 2A3 circuit diagram can be used, provided there is the 4 Volt heater voltage available.
We have a version with the vintage 8pin Side socket, and with the 4Pin UX4 base.