Quad EL34 Mullard Xf4 labeled Philips, NOS specs, same production date v148/ 149/ 170/ 175

Beschrijving

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.

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 nicely matched. 

Valve 1 V148

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

120  mA     13,2 mA/V OK

NOS  NOS

Valve 2 V149

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

120  mA     13,4 mA/V OK

NOS  NOS

Valve 3 V170

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

117  mA     13,4 mA/V OK

NOS NOS

Valve 4 V175

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

116 mA     13,2 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