What made you change to a 6SN7 preamp?

In perhaps the past 10 years or so there seem to be more preamps designed around the 6SN7. I’m on my second after using 12AU, AX7’s. I’ll agree with others regarding the tonal quality of these tubes, the spacious soundstaging, and the realistic textures of acoustic instruments. I use NOS exclusively in my preamp and in my amp, which uses six 6SN7s, due to their consistent quality and sonics (when you buy from a trusted dealer). Due to the increased pricing and availability issues of true NOS, I’ve started to take notice of the high quality of new production tubes. Now there will be no shortage of high quality 6SN’s with the availability of new production. For what it's worth, I’ve never owned a new production small signal tube that equaled the SQ of NOS.

Right, Andy lives for tubes. He tests all his tubes after he acquires them and adds them to his inventory. At the time of a purchase he measures  many different parameters of each tube as if they were to be used in his system. 

@immatthewj these postings may be old, but so are vintage tubes.

http://www.dehavillandhifi.com/6sn7_vt.htm

Thus, a question which controlled for this would ask whether your change in preamp was lateral in terms of construction quality and nevertheless there were improvements in sound which could safely be attributed to the tube?

I upgraded my 6SN7 ,preamp to another 6SN7 based preamp. It was a true upgrade in sonics, but one aspect remained constant, I heard the same characteristics that a 6SN7 provides. Rolling tubes used in the first preamp presented the same type of textures, imaging and soundstaging. There were, of course, many improvements in detail, noise floor, dynamics, and realism owing to the superior quality of the new preamp.

It was said that Vintage Tube carefully tests all tubes for microphonics.

Testing equipment has no way to do this.

The only way is to plug the tube into your component and wait a bit.

True, but the dealer can listen to the tube using a high gain device like a phono preamp. This is what Kevin Deal uses. But this type of test only insures that the tube is non microphonic when it leaves the dealer.

Can using various dampening rings such as Herbie's reduce or eliminate most microphonics?   Or is the microphonic the result of internal parts vibrations?  

@fleschler ,

IME, Herbies can reduce microphonics up to a point. Once a tube has gone full-on microphonic nothing can help. Tube dampers lightly touch the glass envelope and reduce resonances, but in many cases the sound will be affected. It may make the bass tighter in a good way or it may reduce the liveliness of said tube, making it sound dull.

Ralph's UV-1 preamp gave me my first taste of 6SN7's. That small simple circuit produced a huge soundstage, music with weight, and layering of textures. I've moved on to another 6SN preamp and an Atma-sphere S-30 which uses (6) 6SN7 input tubes.

Vintage tube service tests them in circuit, he has many different components to test them in.

@invalid , thanks for posting this. Andy has pics of all his testing gear on the website. Many years of purchases and I've never had a microphonic tube. Also the lowest noise of all my tube purchases.