Siemens E88CC silver shield
This pair of Siemens E88CC tube is from the later Siemens production as it got the silver shield between the plates.
The Siemens E88CC has the date code stamped on a metal plate inside the tube
At the bottom, there is a number between the gold plated pins.
Measurement is done at 2V peak to peak output to a 10k load, using my EM-U 1212m PCI sound card and RMAA 6.1:
THD measurement using the Siemens E88CC, THD = 0.026%
Siemens E88CC grey shield
Siemens & Halske E88CC Grey shield from 1960's - this is the older Siemens production.
The shield between the plates is grey color
There is a AΦ 1≠ 5F date code mark on the tube body
Another example of this date code mark - AΦ 1≠ 3C
THD measurement using the Siemens Grey shield E88CC, THD = 0.032%
The Telefunken E88CC tubes
Telefunken tube has the diamond mark at the bottom
THD measurement using the Telefunken E88CC, THD = 0.035%
The THD test results showed that the Siemens has lower distortion than the Telefunken, that may explains the sonic difference between the two tubes :
"Siemens E88CC - very open, airy, transparent, detailed, and articulate bass with very good triode section matching and low noise"
"Telefunken E88CC - reference quality 6922, open and clear with long-life, very musical 6922, very good resolution-detail, but has some warmth, accurate reproduction"
(Above comments quote from https://www.tubeworld.com/6922.htm)
After listened to these tubes, my conclusion is that if you want the ultimate resolution details, pick the newer silver shield Siemens. If you want good resolution with a bit warmth characteristics, Telefunken would be your choice. The grey shield old Siemens is a balance between the other two, it has excellent details and also sounds musical.
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