In my first article, I introduced four pairs of ECC82 from Mullard, Telefunken and RFT in my collection. Now, let us move onto the 12AU7 and 5693 of the same family as ECC82.    

12AU7

Classic American RCA, GE and Sylvania were once the major 12AU7 manufacturers in the world. Nowadays, the major 12AU7 manufacturers are the Sovtek of Russia and Shuguang of China.

In my collection, I have only one pair of RCA grey plate 12AU7, which is said to be the 1970s version. They are second-hand tubes without original box, which I bought in Hong Kong five years ago. This 12AU7 tube delivers warm but also slow and muddy sound. They didn’t impress me at all. This may be the reason why many used RCA 12AU7 tubes are still available in the market at low price.

RCA has also one grey plate 12AU7 of 1960s version, which has a unique clear top (no silver coating) as landmark. This 1960’s version is said to be of the best sound among other RCA versions of 12AU7.

5963

Europa 80 -  5693

I accidentally came across this tube in one electronics shop some years ago. The tube was etched with word “EUROPA 80 VALVE 5693” in white colour and came with original box.  For fun, I bought two pieces home. 

As I have never heard of such tube manufacturer name in Germany, EUROPA was probably a wholesale distributor in Germany that re-branded the tubes from manufacturers, using their own name. Please feel free to correct me if my assumption above was wrong.

5963 is a premium industrial type, which is nearly identical to the standard 12AU7. The 5963’s max. plate voltage is 300, that is slightly lower than 12AU7’s 330. As far as I know, RCA did produce 5963 tubes with ribbed plates in ’50. It seem possible that these EUROPA 5963 were manufactured by RCA. 

Do they sound good? These EUROPA 5963 are not yet up to range for challenging my favourite Mullard CV4003 series. 

5814

Siemens 5814A

This is a military spec tube. The two I have in my collection were etched with word “Siemens 5814A N75” in white colour. This Siemens 5814A delivers well-balanced sound stage with clear treble and solid mid range.

When compared with Mullard CV4003 series, its mid range is not as detailed as the Mullard, but crisper than the U.S. tubes. In my opinion, the Siemens 5814A is worth trying and for collection.

In next articles, I shall continue with my collection of Mullard CV4003, 6189 and M8136.