What made you change to a 6SN7 preamp?

Thanks lowrider & bigkidz!

Thanks to everyone for posting. Just a couple of thoughts on what I've read so far.

First, clearly, people hear and can articulate a difference; I see patterns in the kinds of differences heard. This is helpful to me in anticipating *why* I might want to try a 6SN7 based preamp. 

Second, @decooney may throw some of the claims into some doubt with his statement:

another factor in responses so far may also relate to some people jumping up a level or two on design and improved parts quality with their next tube preamp purchase.

Strictly speaking, i.e bumping from something like a $1500 12Axx preamp up to a $3000+ 6SN7 based [a higher quality] tube preamp as a normal course of order.

Why? Because if some of you *simultaneously* purchased a better preamp AND a 6sN7 preamp, you could be mistakenly attributing the improvements in sound to the tube rather than the overall construction.

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 realize this is a very hard question to answer, for many reasons. But it is effectively the challenge implicit in decooney's observation.

This is of course, a good point, but I really think, based on my experience that the 6SN7 tube is just inherently a better tube.  Its inherent virtues are such that a talented equipment designer (AKA Ralph Karsten) can do some magic.  I was really surprised when Dan Wright moved from the 6SN7 to the 6922 tube in his digital mods.  I have owned both the Modwright Sony HAPZ1ES which uses the 6922, and the Modwright Sony 5400 ES which uses 6SN7, and there is no question that the HAPZ1ES is a better piece of equipment.  Stock, it was arguably as good as the modified 5400.  After modification, the HAPZ1ES was substantially better, but it took a lot of money to get the top tier tubes from the 6922 family to really allow the HAPZ1ES to reach its potential.  Ralphs observation above that the 6922 tube wasn't designed for audio is not a small point.   If you buy a piece of equipment using a 6922, you better snatch up a Siemens and a spare.  Even the Telefunkens and Mazda tubes aren't in the same class as those old Siemens.  Forget about new production. 

I really think a case could be made that the 101D tube is underutilized, if one judges strictly on the the tube per se.   That tube, properly implemented, has virtues that are hard to ignore.  It has two significant downsides.  It is vulnerable to microphonics, and there are zero NOS tubes out there. It is all new production, and the only great new production tube is the Psvane WE, which go for around $700 a pair. 

If I were designing a preamp, I would work around the 6SN7.  As a buyer, I chose the 101D based Coincident and have no regrets. except when it is time to spring for new tubes.  

I went the opposite direction.  I went from a 6SN7 based preamp to a 6922 based preamp.  I agree with many of the comments about the 6SN7 and happily rolled tubes in and out on a regular basis.  After spending many hundreds of dollars on tubes, I found 2 or 3 pairs that were my favorites, each of which had unique strengths, and enjoyed the ability to change the sound from time to time.

I was a bit apprehensive when I bought my Herron Audio VTSP-360 because I wasn't sure that things could get much better than my previous preamp, but I was immediately struck by how much quieter it was, how much detail it had, and how it presented as good or better of a soundstage and had very precise imaging.  Most of what I've read about it indicates that there are not major differences to be had by rolling tubes, and to date I have yet to open the case and am still happily using the stock tubes that came with it.

There's more to the preamp than just the tubes and Keith works magic with his gear.  I also own the Herron VTPH-2A phono stage which uses a combination of 12AX7 and 12AT7 tubes.  Again, magic happens with the stock tubes.

I was immediately struck by how much quieter it was, how much detail it had, and how it presented as good or better of a soundstage and had very precise imaging. 

It would be lovely if we could attribute the characteristics above to a particular tube; we could all just use that tube and then have state of the art. To address those characteristics has everything to do with operating points, bandwidth, parts quality, grounding, layout, power supply design and so on. The advantage of the 6DJ8/6922 is its linearity and bandwidth (it was used for instrumentation for example) so if you have a non-microphonic tube you'll do well. Since microphonics was not a concern in the applications for which this tube was designed (like television tuners) finding non-microphonic examples is a bit of a task.