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time for another 12au7 type thread..!

Posted by dls123 (D) on April 15, 2007 at 08:26:02

Hi Folks,
Recently I made a few minor changes to my system including:
1. using an 866 mercury vapor rectifier in the preamp
2. switching from Shuguang KT88SC to the new Gold Lion reissue KT88 in the power amp.
3. switching the 4 year old 6H30 output tube in the cd player to a new 6H30DR.
4. Upgrading the cable from the cd player to the preamp.

After all this settled in it sounded very good indeed. The rectifier change made the most difference - astounding change from a 274B type. The preamp designer created a special socket adapter and circuitry change to allow the 866 to be used. The Gold Lions have been discussed here recently. A great tube and a not too subtle improvement. The other changes were more subtle, but improvements.

Anyway, I decided to pull out my stash of 12au7 types and see if my conclusions were still the same with the system changes. The 12au7 is used in the first stage of my 3 stage PP power amp and has a huge effect on the sonic signature of the system. I had settled on a pair of 1951 Raytheon 5814's as my tube of choice several years ago. In the last week I rolled these with early 50's CBS 5814, Amperex 7316, Siemens chrome plates, Mullard short plate 12au7's, Tungsol black glass 12au7's, RFT's, and a few others. The long and short of it is that those Raytheons still are the best - just a bit better than the CBS. Every other tube pales in comparison. Funny this tube business, so system dependent. I know there are many who love the Siemens and the Amperex and no doubt for good reason, but for me the early 1950's Raytheon 5814 is still king with a nod to the early - mid 1950's CBS 5814. The Amperex is nice, but much less bottom end in my system, the Siemens is detailed, but "clinical". RFT's aren't bad, but not great. Mullards are warm and rich, but not as detailed as the Raytheon or CBS..... Some early 1950's French tubes are mediocre in my system. Tungsol black glass sound like all other Tungsols tubes to me...very nicely balanced, but just a little lacking in "soul". Sort of like they were designed by guys with slide rules in their pockets to be very flat in frequency response (go ahead - jump on me!). So guess I'll stick with what I have! Given that my amp runs the 12au7 very conservatively and I have several pairs of the Raytheon and CBS I should be good for maybe 10 - 20 years after I'm dead....Guess if the amp lasts then my kids can have good tubes! Happy spring to all...

cheers,
don

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