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In Reply to: 12AT7 meltdown posted by Rivieraranch on March 16, 2007 at 17:59:41:
Rivieraranch,There are a quite a number of variants of the 12AT7: 12AT7WA, 12AT7WC, 6060, 6201, 6679, 7492, 7728, A2900, B152, B309, B739, CC81E, CK6201, CV4024, E2157, E81CC, ECC801, ECC801S, M8162, QA2406, QA2407, QS2406 and these all have different qualities and ratings, but as far as I know, the above are plug in and electrically about the same- no dangerous loads when in a 12AT7 socket. Several are proprietary to one or another maker. I think the 6060 was only made by Brimar, the A2900 was Bendix, the M8162 was only by Mullard, the 7728 was a CBS/Raytheon and so on. Several companies made ECC801S, with Telefunken the famous one, but there are also Siemens and I think Mullards
My favourites are the 6201s which is the military designation 12AT7 ruggedised and low noise, low microphonics, often a long life tube with gold pins. The 12AT7WA is a US designation that's very similar. The Philips made 6201 is a really good tube. Just today, after trying to buy them for four years, I received some 1963 Valvo 2- mica blue label, gold pin 6201s, not the amazing triple mica ones, but quite wonderful in themselves. The eordinary Valvo 6201 of the mid 60's to late 60's is just fine. I think the Philips 6201s were all made by Philips, Hamburg, though there may have been late orange globe labelled Amperex made by Mullard, Blackburn.
For a punchy, dynamic 12AT7, I like the triple mica Siemens E81CC- extended, detailed, and natural. These are especially wonderful in slightly dark vintage stuff like McIntosh.
If you're after a really lush, tube for your Jolida, look for Sylvania 12AT7WA triple mica, black plate, square getter tubes. These are almost shockingly deep, and perhaps very slightly dark, but make a really great sound with a wide, deep soundstage in the right gear. I bought 4 of these about three months ago at about $7 each. These are better in modern gear than vintage as in vintage they may be too dark.
Another surprisingly good 12AT7 is the older black plate RCA and even the ubiquitous GE triple mica 6201- there are millions of these made for computer use- are quite alright and very cheap.
If you like the rare and unnecessarily expensive, the Telefunken ECC801Sis very nice- the regualar Telefunken 12AT7 I find completely ordinary, and the Mullard M8162 is wonderful, but only the early ones. Later Mullard 12AT7s- the ones with all the KKQD & etc. labelling, to me are on the "avoid" list.
For overall balance in your Jolida, my suggestion would be Philips 6201- check German Ebay for early 60's Valvos. I bought some nice early 70's military labelled Valvo 6201s for about $20 each. You might try the admirable RCA 6201 and perhaps Raytheon triple mica 12AT7WA as well, as these are not overly expensive to have around for some comparison. If your taste runs to the punchy and authorative bass, the Siemens triple mica E81CC could be the one. I mention the triple mica as there were late E81CC that are 2 mica. These are labelled only "SIEMENS" in block letters while the triple mica has the intertwinned S&H logo over the "Siemens" These actually are just fine- better than the standard Telefunken ECC81 in my view,, but the triple mica one.
I've noticed that premium 12AT7s are getting quite expensive now- the Telefunken ECC801S is a $100 tube NOS and the 6201 offered now on US Ebay seem to be almost all the GE 6201- not bad at all, but not as interesting as several others. There are, however bargains, and I bought a couple of the later two mica Siemens E81CC for about $12 each and the RCA, Sylvania 12AT7WA, and older triple mica Raytheon seem to me to be real bargains.
Let us know what ends up working for you in your Jolida.
Cheers,Bambi B
Follow Ups:
'12AT7: 12AT7WA, 12AT7WC, 6060, 6201, 6679, 7492, 7728, A2900, B152, B309, B739, CC81E, CK6201, CV4024, E2157, E81CC, ECC801, ECC801S, M8162, QA2406, QA2407, QS2406'Hi ,
Out of the above E2157 (experimental) , QA2406/7 and QS2406 can be ignored ; you'll never see one ! I really don't know where you get the 'low microphonics / military' thing from . Ruggedised valves as used by the military were built specifically or selected upon test in the factory . Ruggedisation has completely different criteria to low microphony . Add 13D9 , E180CC and 5965 to the list , these are very similar to a 12AT7 and should work fine .cheers
Thanks for all the information and impressions about the different tubes. I have 6 pairs of CV4024 KQDD, etc., and this tube does not sound bad. Why to do say they should be avoided?I also have a pair of 1956 JAN Sylvania 12AT7 AF tubes with triple mica spacers, black plates and square getter. I have not used them in the Jolida 302B yet so I need to plug them in. I would like to find some more. Is that what you have? Maybe we can talk turkey.
I have a friend who is crazy about the 1980's JAN Phillips 12AT7WC's; feels it is a darker tube. When I compare it to the earlier tubes it comes up short; it has thin micas and does not look that rugged.
Riviearanch,As I consider my NOS tube collecting to be more or less "finished", I realise I've probably focussed disproportionately on the 12AT7- I have 80 NOS to fill 8 sockets, but it's a tube that has surprising sonic influence in the gear I have that use it.
With the Mullards, I should have been more specific, it's the mid-late 80's KQDD- the very last runs that I find to be unsatisfying- a little hard. They're not terrible by any measure, but my attitude is that they are often overpriced only because of the Mullard name and sellers try to confuse buyers by suggesting these are sonically the equal of the earlier ones. For the prices these command today- I've seen sellers try to get $30-40, one can find much, much better 12AT7s and that's why I recommend avoiding them. It's interesting to me that as time goes on, the line between the really seldom seen and great old production tubes and the late, far from spectacular is being blurred.
The 80's JAN Philips is again from the end of old production. My microphone preamp (6-12AX7, 2-12AT7) came with a pair of Philips ECG (blue green print) 12AT7s- these may be the identical construction to your friend's JANs and these tubes are probably the worst tubes I've ever heard- hard, tizzy, dark, and dry. It's odd these came up as only yesterday when repacking some tubes, I found these Philips and I really thought I'd tossed them in the bin five years ago!
The 1956 triple mica Sylvanias you mention are likely to be the exact ones I mean. These have the gold print. I have also some JHS labelled with a light green print. The first pair of these I bought were in 1958 Air Force boxes and this tube in the right place is just amazing. I would encourage you to try these in your Jolida before acquiring more. In the meantime, if you want to hear something of the range of the 12AT7, consider trying triple mica Siemens E81CC which will help reveal what the fast, punchy approach does in your amplifier. Then, for the middle ground, the early 60's Philips, Hamburg 6201 is a great all rounder- just fantastic sense of space, natural timbre, and detail.
I would enjoy hearing what your experiments tell you!
Cheers,
Bambi B
Trying 2 1970's IEC Mullard 12AX7's with the 1956 JAN Sylvania 12AT7's in the amp with NOS Svetlana EL34's turned out to be a very satisfying combination. With vocals there is no grain; a nice open presence. Now I will switch to CV4024's in the 12AT7 position.I bought my CV4024's very cheap so they are a good value.
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