Recommended 12au7/5814s for Atma-sphere MP-3

In the MP-1, starting from the rear, the 1st two positions are wired differentially within a tube and the 2 tubes are then in parallel. This is the bottom of the cascode. The 3rd tube is the top of the cascode. So the 1st two make the most difference.

In the MP-3, the 1st tube from the rear is the bottom of the cascode differential, and the 2nd tube is the top.

Generally speaking the noise importance of the tubes decreases as the signal progresses from the rear to the front of the unit, but that is not to say that the final tube is not sensitive to noise.

Generally we advise people to stay away from NOS in the phono section because of tube aging. In this case, not the NOS tubes, but the OEM tube, which is Chinese. Unless those tubes are new, they will be noisier than they should, so often NOS tubes replace them, and then the preamp gets accused of being noisy when really what is happening is the NOS tubes, while being quieter than the OEM tube (which might have gone down hill its own self), are still not quiet *enough*.

That is not to say that you can't find NOS tubes that *are* quiet, but they are rare these days.

Well, it started with a question and now I have taken the plunge. I'll be using Mullard 12au7, RCA Blackplate 12au7, RCA Cleartop, RCA 5814, and Siemens 5814 and mixing and matching those with RCA 6SN7 GT Greyglass and Sylvania 6SN7GTA early on the MP-3 - all fun and games as I find the best combination for my ears. On the M-60s I will be using RCA 6SN7GTBs on the front tubes and Sylvania 6SN7 GTBs on the back tubes with GE 6AS7s matched by RAM Labs. Thanks for you comments and private e-mails. And by the way, the units sounded pretty darn good with the Chinese tubes the units came with.

Isn't it great having gear low enough in distortion that even single tube changes are made transparently obvious.

Now - if you have a phono section in your MP-3, just wait until you start rolling phono input load resistors. Thats as much fun and a lot less expensive. :-)

Tim

Rodman99999, or anyone else, will the 12BH7 tube work in the MP3 as a replacment for the 12au7? Is that a safe replacement? Ralph?

12BH7s have twice the filament current, but you should be able to run them. They are based on the 6SN7 geometry- I'd be interested in what you think.