9.7.06
Easytune,
I've tried a lot of 12AT7s:
Siemens E81CC- 3 mica- NOS
Siemens ECC81- NOS
Valvo 6201- GP- Hamburg- NOS
Mullard M8162 NOS
Sylvania GB 6201-steel pin NOS
Sylvania GB 6201- gold pins- NOS
Amperex Bugle Boy-France- NOS
GE 6201 5 star- 3-mica NOS
RCA -HP- NOS
RCA 6201 2-mica black plate- NOS
Sylvania JAN 12AT7WA 3-mica 1958 -NOS
Sylvania 12AT7WA-Gold Print- 3 mica -USED
GE -NOS
Westinghouse- black plate-NOS
Telefunken ECC81- USED
Philips JAN- NEW
ARC -USED
GE 6201- 3 mica, sq gtr- NOS
Telefunken ECC81- NOS
Telefunken ECC801S- NOS
The 12AT7 makes a surprising contribution to the sound of the 6 pieces of tube gear I use it in and I've played with this type more than most others.
I would characterise it by first suggesting the two 'extremes' of sound I found. The triple mica Siemens is clean, fast, punchy, and lively- detailed and deep. On the other end is the Sylvania 12AT7WA. These are triple mica late 50's tubes that are almost impossibly lush and deep, still detailed but more 'forgiving' than the Siemens. For some reason, Sylvania really got the 12AT7 right and the suggestion for the Gold-Brand 6201 is a good one. In the middle are the various Philips models and the one I would suggest for VTL would be the Philips 6201- gold pin. These can be made by Philips Holland or Germany. I'm using a pair of Hamburg ones (from seller 'tubemonger' who sells on Audiogon sometimes) in my microphone preamp and I find these to be balanced, have great frequency extension and are smooth, quiet and great detail.
The Telefunken ECC801S mentioned elsewhere is a nice one too, but it has a speical sound- a bit 'delicate' that I think might be too specific a type just to experiment with- and they can be quite expensive now. Mullards too are also a bit specific to the midrange, but can be very nice. I agree with the poster that the M8162 is fantastic. If you try the M8162, there are several versions, and the older the better. If you're wealthy ($50-60 each), there is the ultimate 12AT7, the Valvo, Hamburg, pinched waist blue label 6201.
It may be that as an Audio Research user, I gravitate towards the faster, more neutral tubes- and I find I just never dislike Siemens tubes. If you find the VTL to be a bit soft, the Siemens E81CC can wake it up a bit- and that's what I use in my old McIntosh stuff too. If you want what I call the 'Bing Crosby 1939' sound- it's the Sylvania. With Siemens, always be sure they're 'Siemens and Halske'- with the little intertwinned 'S&H' and not the later two mica versions with just "SIEMENS' in big block letters. One slightly eccentric idea is the old square-getter triple mica GE 6201- these have a great bass and are quiet, detailed, and rugged. The nice feature of this one- I just bought the GE NOS a couple of months ago for $8 each. This is the tube I plan to use as 12AT7 in my power amps and Audio Research SP10 power supply. The normal GE 12AT7 is a mediocre one, but this old 6201 is a 'sleeper' in my view.
Overall, I'd begin with Philips, Hamburg 6201. The gold pin Valvo, Hamburg 6201 will be the same tube and sometimes less expensive.
Cheers,
Bambi B