The first shipment of ELROG tubes arrived today.
The tubes are nicely packaged as matched pairs. A measurement certificate signed by Dr. Schaffernicht comes with each pair:
Each tube has it's individual serial number, stamped on a metal plate inside the glass:
Craftsmanship is exceptional. The plates always have the same alignment with regard to the pins, which is not always the case with NOS tubes.
A NOS GE211 / VT4C in comparison to a ER211:
They are about the same height. The ELROGs have a slightly larger diameter. Earlier ELROGs had a smaller diameter glass. This was changed for the final series production to give better heat dissipation. The most apparent difference is the location of the electrode system. While the system is mounted in the upper half of the tube in the GE. ELROG mounts the system close to the base, which gives much shorter wire lengths between bins and electrodes.
I ran some measurements on a curve tracer. Comparing a NOS GE211 with ELROG. Unfortunately my tracer only allows plate voltages up to 400V.
Here is the set of plate curves of the GE:
On the X axis the scale is 50V per division. On the Y axis we have 2.5mA per division. The grid steps is 5V, starting with 0V with the left most grid line.
The ER211 in comparison:
Remember this is only up to 400V and 20mA. These curves show why these DHTs are so great. They are exceptionally linear. The ELROG is remarkably close to the GE the grid lines are a little bit steeper with the ER211 indicating slightly better transconductance.
The tubes will be tried in various amplifiers and I will provide feedback on the sound. Stay tuned!
Send an email to thomas -at- vinylsavor -dot- de for inquiries about these tubes.