EL34 Mullard Xf2 branded Pope NOS/NIB same month/year V243 244

Description

Here is a pair NOS Mullard Blackburn Xf2 EL34 valves branded Adzam.

Description

The Mullard Blackburn Xf2 dark brown base EL34 valve is introduced as a successor of the famous Blackburn Xf1 EL34 in the sixties, this was the second EL34 version made by Mullard Blackburn. The Xf2 type EL34 was the first version with single halo ring, after this type came the Xf3 and Xf4 which ended production in Blackburn in the late 1970s. The tubes are new in box and have NOS test values. Both tubes are produced in the same month: July 1967.

Sonics

The sonics of the Xf2 EL34 is typical for the Mullard Blackburn sound character and is among the worlds most musical EL34 tube known for its pronounced liquid midrange.  I refer to the many reviews on the web. And they seem to last forever.

Test results*

Valve 1 V341	Ia (plate current): Transconductance (Gm): Gas test, Shorts test:	108 mA       12,0  mA/V OK	=  NOS = NOS
Valve 2 V341	Ia (plate current): Transconductance (Gm): Gas test, Shorts test:	117 mA 12,8  mA/V OK	= NOS = NOS

Telefunken tube values for new unused tubes:

• The rated emission value for a new EL34 is:  100 mA. 
• The rated transconductance value for a new EL34 is:  11 mA/V . 

For Telefunken specs info see last picture 

Test condition & 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) = 265 Volts, Ug = -13,5 Volts and Uf = 6,3 V ± 3% (factory conditions). Please read our test page.

Summarized description