Interestingly, I have a few old volumes of the Mullard Technical Handbook (essentially a designers' guide to using valves). Volume 1 covers the normal run of the mill line of valves, and the data sheet for the EL84 does has 'characteristics' that differ from the PL84 and the UL84 (most likely because they are quoted at different anode voltages. Text: Mullard Mullard Mullard Mullard Mullard OC44M OC45 OC45M OC57 OC58 Mullard Mullard Mullard , ud io output HF power OC26 OC28 OC30 OC35 OC44 OC71 OC72 OC73 OC74 OC75 Signal , A D 140 A D 1 49 AD161 A D 1 62 â ASY55, GET874, NKT612, NKT125, OC44 , 2G344, 2GT102 , ASY54, GET874, NKT612, NKT125, OC44 , 2G344, XA112 NKT612, NKT674, 2GT117 ... I have been researching treble boosters and I have come across a couple of sites that claim the Mullard OC71 transister offers a smoother less brassy sound than the OC44. Does anyone here have any experience with the two transisters? What do t6he minds here think of these two transisters? Both are NOS.

Of particular note is the Mullard "Lockfit" range. The BC147, 148 and 149 can be replaced with BC107, 108 and 109 respectively - even the lead configuration is the same. While germanium transistors have become mainly obsolete, a small range is still being manufactured.