What made you change to a 6SN7 preamp?

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.

Bought a used Ultraverve pre here on Agon, compared it side by side with my highly reviewed, more expense 12AU7 pre. Immediately sold the 12AU7 pre. Soundstage opened up, instruments and voices sounded more lifelike to me. I realized it was the sound my system was missing. Kara of Dehavilland built me a Mercury III and I rotate the two pre amps. I learned from this:1) more expensive is not always better 2) you can’t know what you are missing till you try it as it may be the sound you want 3) the preamp has a HUGE impact on your system. I am not saying 12au7 pres are not good, just sayin for my ears I like 6sn7 much better.

@atmasphere Ralph, I think you were reinforcing the point I was trying to make that it's not all about the tube?  Interesting to hear the 6DJ8/6922 was intended for use in TVs.

@hilde45 I don't have any experience with the Quicksilver preamp you have listed in your virtual system, but I think you'd find the Herron preamp a night and day difference.

@lowrider57  Thank you for relaying the story about that upgrade. It bears on my question directly. Very helpful.

@moofoo  Your example, too, bears on the question. And as others have said, there's no substitute metric for actually hearing it. Expense, tube, design are all relevant to the question, though. 

@big_greg  Thanks for your comment about the Herron. I need to sell something before buying anything else, but I'll keep my eye on that Herron. My Quicksilver got upgraded with Mundorf and Vcap caps and sounds pretty good. A night and day difference would really be the reason to change.

There are lots of possible tube to use. My favourite preamp uses 6GK5s.