Quad EL34 Mullard Xf2, Tungsram label, NOS/NIB V21 22 354 355

Description

Here is a matched Quad NIB Xf2 EL34 tubes made by Mullard in Blackburn, UK. Labeled Tungsram

The tubes pairwise have the same production periods!

Detailed description

These Mullard Xf2 EL34 tubes with single halo-getter and welded plate are from the Blackburn production site.The EL34 is a transmitting beam tetrode. The old Mullard production from the past century is known as the ‘crème de la crème’ of the EL34. These tubes deliver superior sonics compared to the Chinese and Russian new production EL34. Sonically some prefer the old welded plate types above the later stapled plate versions. I refer to the many reviews on the web.

The tubes are pairwise from the same periods and have production dates September/ October 1968 & September/ October 1969. All four tubes are from a former stock of the Dutch post (PTT).

The Mullard EL34 Xf2 series is considered by many as an outstanding sounding EL34 tube; a lot better than todays production!

The quad has NOS test values and looks. 

Note: my tubes are often not the cheapest. But is very hard to find better tubes !

Test results

The measurement data below show that the tubes are matched. 

Valve  V21

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

105  mA 12,2  mA/V OK

>  NOS > NOS

Valve  V22

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

111  mA 12,8  mA/V OK

> NOS > NOS

Valve  V354

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

104  mA 12,5  mA/V OK

> NOS > NOS

Valve  V355

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

108  mA 12,3  mA/V OK

> NOS > NOS

Telefunken measuring 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