Beschrijving
Rare Quad Telefunken EL34 tubes produced by Mullard in Blackburn, Uk.
Detailed description
These Telefunken EL34 with single halo getter and welded plate are a 1961 production of Mullard Blackburn. All four tubes have NOS specs. One pair of tubes has date code Xf2 B 1A1 (1961 first week of januari) the other pair is produced in the same year in februari (date code Xf2 B 1B2). The quad has NOS test values and excellent looks.
Note: my tubes are often not the cheapest. But it is very hard to find better tubes !
Sonics
The Mullard Xf2 EL34 is considered by many as an outstanding sounding EL34 tube; a lot better than todays production! I refer to the many reviews on internet.
Test results
The measurement data below show that the tubes are platinum matched.
| Valve
V334 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
95 mA
11,8 mA/V OK |
> NOS
> NOS
|
| Valve
V335 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
95 mA
11,9 mA/V OK |
> NOS
> NOS
|
| Valve
V336 |
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
93 mA
11,6 mA/V OK |
> NOS
> NOS
|
| Valve
V337
|
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
86 mA
11,0 mA/V OK |
> NOS
> NOS
|
Factory Specification for new unused tubes (Telefunken/Philips/etc.)
- The rated emission value for a new EL34 is: 75 mA.
- The rated transconductance value for a new EL34 is: 11 mA/V.
As specified in AVO Valve Data Manual 23rd edition 1981.
Test conditions & equipment:
Mutual transconductance, plate current, gas and shorts test equipment: AVO Mk IV (Dutch army tester) , AVO Valve Data Manual 23rd edition 1981, RFT stabilised mains, Utracer3+, Philips PE 4832, 2x Korad KA3005P programmable power supply, 2x Keithley 2700 and 2x Fluke 145. Test conditions: Ua (plate voltage) = 250 Volts, Us (screen voltage) = 250 Volts, Ug = -13,5 Volts and Uf = 6,3 V ± 3% (Mullard conditions). Please read our test page.
Note: Look for a detailed description of testing methods on the site: tubes4hifiaudio.ctpu.nl/tube-testing-quality-control/
Summarized description
| Tube type | EL34 |
| Quantity of Tubes | One quad |
| Brand | Telefunken |
| Manufactured by | Mullard Blackburn, UK |
| Date code | 1961 code: Xf2 B 1A1 & Xf2 B 1B2 |
| Plate Construction | Welded grey plate |
| Getter Construction | Halo getter |
| Print Condition | Excellent; see pictures |
| Box included | Generic white box |
| Equivalent tubes: | 6CA7 |
| General test results | NOS |
Please read our test and shipping policy before buying !
