Review : Mullard ECC82=12AU7=CV491 ,long plate,D getter,1950s.(50年代製,長屏,方環)
The best Mullard 12AU7 is the 1950's 17mm plate square getter version. It can be designated 12AU7, ECC82 or CV491 depending on the customer order. This tube was made up until 1958 and can be identified by the top line of the date code being k61, the 1 meaning Mullard's first version. It is also possible to find this tube branded Amperex Bugle Boy Made in Holland. In 1958 the getter shape was changed to a large O-getter, but this is still the same tube.The k62 versions are still excellent, but not as good. The Telefunken ECC802S is a very linear, uncolored tube with slight euphony to the mids, whereas the Mullard is fat, very colored, warm, and has great clarity with warmth on top. The Amperex 7316 early version, with a D-getter, is not as fat, lying sonically between the Mullard and Telefunken, it is extremely sweet with a euphonic rounded midrange and good bass. Later Amperex 7316's, particularly orange globe branded ones, are notably inferior.
I have found that the old logo ECC82 is consistantly better than the newer logo ECC82 and the CV4003 or M8136. BTW I have tubes that have both CV4003 and M8316 printed on the envelopes, however there is a long plate version (ECC82) thats does sound better again although the cost may not justify the expenditure.
The Mullard M8136 is a box plate, just the military numbering also can be found marked with a CV designation or ECC82. Personally, although this is a good and easy to get tube (they are all late Mullard stock with tons around), I feel the Mullard reputation rests on the earlier tubes - the long plate D-getter CV491 is spectacular, incredibly lush and warm, blows all over the Amperex 7316 (which is in itself a great tube). It's funny how sought out the later tubes are, when the early stuff is really the legendary tube. Just my opinion, of course.