Quad EL34 Mullard Xf4 labeled Philips NOS/NIB v174/188/189/190

Description

Here is a matched Quad of EL34 tubes made by Mullard in Blackburn, UK, Labeled Philips

Detailed description

The Mullard EL34 with single halo getter and stapled plate is a 70’s production. Often the later produced Mullard EL34 has a stronger emission than earlier series. This is also the case with this quad. All have very strong (much better than NOS) specs.

All three tubes have date code Xf4 B 0D3 and one Xf4 B 0E4 which puts their production date in April and May 1980.

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

These tubes deliver superior sonics. I refer to the many reviews on the web.The quad has NOS test values and good 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 very very well. 

Valve  V174

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

127  mA 13,6  mA/V OK

NOS NOS

Valve  V188

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

124  mA 13,8  mA/V OK

NOS NOS

Valve  V189

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

124  mA 13,9  mA/V OK

NOS NOS

Valve  V190

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

126  mA 13,9  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 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) = 265 Volts, Ug = -13,5 Volts and Uf = 6,3 V ± 3% (factory conditions). Please read our test page.

Summarized description