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The 12AU7: A veritable cornucopian panolpy of plethoras

jnr,

The 12AU7 has quite a range of sounds possible. I have lots of tube gear- 13 pieces, but use only 6- 12AU7 in four pieces: 1,2,1,2 - and this all vintage: McIntosh MX110, MC240, MR67 and a Scott 330D tuner.

Siemens 5814A: The 12AU7s in metal cans must be the military issue of the very desirable Siemens triple mica 5814A- I've never heard of another tube in the can- but nonetheless, the triple mica Siemens 5814A is still my favourite 12AU7 version. I find these extremely dynamic- very fast, punchy, and detailed, which is why I like them in vintage gear- wakes them up a bit. Perhaps in modern gear they might be a bit aggressive,... Be aware that in my experience, the Siemens 5814A requires perhaps 40+ hours burn-in to be fully developed.

Amperex ECC82: The best all-round 12AU7 which is not impossibly expensive is, for me, the ordinary Philips ECC82 of the early 60's. This may be Amperex, Philips, or Valvo labelled and then there's the Amperex Bugle Boy, for which large sums are exchanged, but I've never been able to tell the Bugle Boy from the others. The early long (17mm) plate ,D-getter versions must be just fantastic and if your monoblock are "very nice and expensive" you might consider going for these early ones. There is also the 7316, the premium Amperex 12AU7, and I have only one of these, and it's quite amazing. These are very hard to find and expensive- mine was $40 two years ago and the most expensive single tube I've bought. Our friend tvr2500 knows the 7613 well and will perhaps comment.

CBS 5814A: One 12AU7 that really amazes me is the mid-50's CBS 5814A, black plate, stirrup getter. This is a smooth, articulate, and refined tube with plenty of punch and excellent bass- a "deep" tube with authority. Perhaps few people seek them out specifically so they're sometimes quite a bargain. It was a fluke, but I recently bought 4 of these testing NOS as part of a lot for $1 each. I was prepared to pay up to $20 each! I'm using this one in the 1958 Scott tuner- amazing.

RCA 5814A and "Cleartop": The RCA "Command" 5814A is a bit of a sleeper in my view- very dynamic and smoothly balanced. These are also often reasonably priced, I recently bought NOS in the box for around $6 each. The "cleartop" sidegetter RCA is another nice one- but for me it must be in the right spot- namely vintage. It's speculation on my part, but these may seem too bright in modern gear and I'd look into comments from those using the cleartop in modern stuff.

I'm surprised a bit at your description of the JAN Philips as being more open and dynamic than the Siemens- I would have predicted the opposite, but it's true that newer gear is often refined around the sound of more commonly available tubes- it has to sound good -and allow consistency.

I don't know your components and taste really, so my overall recommendation would be to find a set of good, tested early long plate Amperex or at least good early 60's Amperex ECC82. Also, if you haven't, you might be able to save a lot of effort and costs and first try the Siemens until they're fully developed sonically- I think these are a great one given the chance.

Cheers,

Bambi B


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