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

I have an MP-1 which does not use the 12AU7 so I cannot compare the relative influence of those tubes with the 6SN7.

In the MP-3 I believe the two sections of each channel's 6SN7 are part of its circlotron output with each cathode in a tube handling one-half of the wave form. (Hopefully Ralph will correct if thats wrong. :-) Thus, it is v. important there be a decent match between the sections within that tube, and that the tube be quiet. As Tvad notes, 'quiet' is a critical attribute - moreso for the preamp than for the amps - so a dealer (such as AndyB at VTS and others) who will screen for noise may save you some money in the long run even if he charges a bit more for the tubes.

The brand/vintage of each channel's 6SN7 will have a real impact on the preamp's sonic character. Some contemporary tubes are 'not bad' - eg., I and others who've tried the Electro-Harmonix 6SN7 find it tends toward a timbre not far from a Sylvania GTB. However, quiet NOS versus a Chinese or Russian 6SN7 in that position, is, imo, not much of a contest and for me NOS are worth the extra rubles. While you can spend a lot of money on the more exotic 6SN7 varietals (bad boy chrome domes, round plate tung-sols,'W's, etc.) a couple nice Ken-Rad, Sylvania, Raytheon, or RCA GTs/VT-231s shouldn't break the bank - especially if you start with used tubes to learn your own sonic preferences. If you haven't seen the head-fi 6SN7 thread, you can read it here.

Fwiw, I've found Herbies tube dampers do their thing nicely on the line stage tubes as well as in the phono section. I use them on 6 out of the 10 6SN7s in the MP-1's line stage, and on 6 of the 8 12AT7s in the phono section. Best of luck tube rolling your new MP-3!

Tim

I have Herbies on every tube for good measure. I did spring for the RCA GT (Grey Glass - 1940s)that are suppose to be very well matched and I'm keeping my fingers crossed, quiet. I think I'm going to stick with Sylvania early GTBs for the M-60s, though I might roll some GTs in putting them into the mix helps. Is everyone in agreement that GT/231s (assuming they are quiet and well matched sections) generally sound better than GTA/Bs?

I haven't done much rolling with my MP-1, but I'm using a Raytheon 6SN7 in the forward position(differential amplifier where all LS gain is performed), a matched pair of 6SN7EH in the circlotron, and 6SN7EH in CCS. IMO the latest EH production sounds clear, extended, & musical. The front 6SN7 is a good place to experiment with NOS tonality. In the phono section Mullard 12AT7(selected for low noise by Jim Mcshane), improvement upon the stock Chinese tubes both in quietness & sonics. The first two 12AT7s in the phono section circuit are in parallel, forming together the top half of a cascode with the third tube. When rolling the phono stage, you would probably want to replace the first two 12AT7s with the same type of low-noise NOS tube.

Jtimothya, great reading on that link. Thanks.