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

While I understand that to some extent, every tube matters, do the 6sn7s make as noticeable difference in the MP-3 compared with the 12au7s? That is, are these slots worth spending NOS money on?

On the M-60s, do the front and back 6sn7s (V1? V2?)get equal billing for NOS upgrades, or are the V1 spots more sensitive in terms of impacting the sound? Additionally, my understanding is that the V2s in the M-60s in the back have to be GTA/Bs to handle the voltage.

When does the bidding start on the Bad Boys?

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.