Portrait of a tube
EL34S SHUGUANG

Author Jac van de Walle

I received this pair of tubes from my friend Hans Jörgen Dorn, who told me they were defective, and perhaps I would like to see what kind of tubes these are. He bought them many years ago.

First thing I noticed, the Shuguang logo is looking totally different from the chinese factory logo, and it is now with dragons. This logo I never saw before. Then the tube is called EL34S. Now, in tube world, any "S" version stands for Special, which means one of the parameters, like maximum dissipation, or plate voltage exceeds the standard limits for this tube type (One example is 2A3-S from Emission Labs, which can replace a standard 2A3. but can also be used at higher power)

Indeed with EL34 there was the Philips version that could be used up to higher voltage of 750 Volts. With great modesty, Philips did not call this an S-Version, just normal EL34, but in the datasheets you would see noticeable higher maximum values. In a way, this is also wrong, since designers would use the Philips datasheets and tubes, and everything looks fine at first. Then, many year later, someone replaces the tubes, and he takes for instance lower cost JJ tubes. Of course these will blow up since they fail at the higher limits.

However, with this Shuguang EL34S there is no reference as to what "S" with this tube is supposed to stand for. I looked inside, but I could find nothing inside to explain the "S"

Before you look at the pictures, read the following: There are pentodes, and beam tetrodes, and these work not the same way. EL34 is pentode, and 6L6 is a beam tetrode. Beam tetrodes have not such nice curves as pentodes, and are lower cost to produce. I had this broken pair of Shuguang "Big bottle" EL34S, that broke down in an EL34 amplifier after short time. I tested the filament current before breaking the glass, the tubes had correct 1.5 Amps for EL34. So they're not 6L6 in another jacket. They have real EL34 filament current. Still, for me EL34 has to be pentode, and what came out was..a beam tetrode.

On the box it says: "Shuguang Golden Dragon power tubes are the result of a collaboration of British Audiophiles, engineers, and the Shuguang tube factory" Well, it seems the Chinese were in great need for assistance ;)