What's the best 6NS7 tube you have tried in your Atma-Sphere MP-3 preamp?

Of course, a 6SN7 GTA can be a good fit in a given situation. It all depends on the other components of the setup, preferences, acoustics, etc. A SET or a PushPull have a completely different set of requirements, as the power transformer is already a source of timbre. An OTL is a completely different world; the sound has to come from the tubes. I've been working with these OTLs for about 17 years now, and my journey has also been one of trial and error.

As Pindac also indicates, a single-tube setup is simpler, but this comment deserves some qualification. With an MP-3, it's much easier to determine the character of a 6SN7 tube because it only uses one pair. But that's also its limit. My best experience there is with a Sylvania GT Bottom Getter (VT231 is still reasonably affordable), which delivers a lot but, to my ears, doesn't yet have the right timbre on its own in an OTL. Incidentally, the 12AU7 also plays an important role here, but a good, silent NOS is difficult to find. It's important to consider the power amplifier in your approach. With solid-state, it is what it is. But if you have an M60, you can further build on what the MP-3 delivers.

My strategy is to ensure the preamplifier is perfectly matched in terms of sound, spatiality, and detail with the right tubes. Slam and engagement don't play a (major) role in my approach there. I address those in the power amplifier. The more tubes in the chain that determine the sound, the more compositional possibilities you have to achieve the desired result. With a combination of an MP-1 Mk. 3.3 (latest update) and an MA-1 Mk. III, you have six tubes that significantly determine the sound. On the one hand, that's fantastic, but on the other, it presents a complex challenge.

Whether it's an M60 or another Atma-Sphere amplifier, based on my strategy, the engagement, slam, and experience (where you're sitting in the concert hall) should be created there. Regardless of which Atma-Sphere power amplifier model you use, I would recommend using a Linlai GT E and, in the case of the M60, completing the process with a second tube. With the MA-1, you have two tubes to do that.

Pindac rightly points out that not many have the necessary tubes for such an experiment, at least if I'm interpreting his/her comment correctly. But I think that if you have an MP-3/M60, and especially an MP-1/MA-1, such a setup deserves a carefully selected set of tubes. That's the corresponding investment. Not everyone will be as crazy as I am to amass a tube collection that now represents the value of a small car. But perhaps there are enthusiasts nearby who could borrow some things and/or try them out together. In the Netherlands, as a hobby, I'm willing to occasionally visit an Atma-Sphere owner with my tubes by appointment.

My Pre Amp to be commission designed / built by my Power Amp' designer / builder over 20 years separate,. Is  Pre Amp' Design to deliver a range of influences on the System End Sound. 

Two Tube Types are to be used as independent channels and a SS Channel is added as well.

Variable Gain is also an option I have selected. 

When it comes to Valves to be trialed, I have been very fortunate, I have a decent measured selection that extends from the 1940's to the 00's

A friend has a substantial selection of Valves from Two Generations of  collectors. 

Loaned Valves always measure above factory Spec". These are Tip Top always close matched on each halve. 

Making a change to an End Sound by changing a Tube is for everybody with a Valve to be changed

Transforming a System to one that is unrecognisable, where the betterment is judged by End Sound and Gape of the Dropped Jaw, as a result of creating a permutations throughout a system. This is a gift belonging to only a few. 

Such changes when created are imagined as being unsurpassable. 

Pindac, I can't speak for your system, of course, but I can tell you that with a little patience, you can make an Atma setup sound so amazing that people wonder how the music is actually being played live for them. And they'll be shocked when someone goes wild on a drum kit, etc. Believe me, there's nothing exaggerated about that. Or the voices can be so tangible that if you stretch your arms, you can almost touch the artist. But that, of course, depends on many factors. I truly believe that with some time and effort, anyone can deliver a performance that ranges from acceptable to truly exceptional.

I've spent a fair bit of time experimenting with 6SN7s in my MA-60.  After considerable trial and error, I've settled on Ray's select in the back outside positions (very alive and clear tubes without a hint of etch or grain), a sylvania chrome dome in the center back position (smooth and clear), and am currently running some NOS tung sols in the front position (very detailed and realistic).  I have a number of Sylvania and RCA tubes that I cycled through before landing on this combination.  I am going to try a pair of Linlai in the front positions, because why not?

I agree with revinylized that the Atma-Spheres can sound glorious with the right combination of tubes and associated equipment.  

@car123 

I haven't tried the Ray, so I have no idea or opinion about it. The Linlai fits well into my setup and what I want to achieve overall. Of course, there are many ways to Rome. In my MA-1, I've combined it with the Melz ribbed anodes (without the holes), as mentioned above. I'm experimenting with the third one. On Monday, I'll be getting a TS T-Plates with black coated anodes for a bit more rounded tones and a slightly warmer midrange. I still have a few candidates for this position, which will put me at the front of the concert hall.