With the Kit1, I was quite excited about the fact that 6SN7s is the input stage tube. The legendary tube type used in so many fine stereo equipment and I always wonder how special it may sound. But my feelings are quite different now that having gone through so many different 6SN7s. The search for the right 6SN7 for me was so difficult to the point that I felt that it may not have been my cup tea.
I was baffled by so many variations of 6SN7 tubes that exists and readily available in the market. They are generally reasonably priced even the NOS vintage tubes except for few that are highly collectable. The first thing I did was to call Andy Bowman of Vintage Tube Services. I have already dealt with him few times before when I got excellent vintage NOS tubes from him at reasonable prices. He seemed to be very knowledgeable about 6SN7s judging from his website. I told him that this is my first equipment with 6SN7 so I had no idea what to look for or which tubes to get. He told me that, in general, RCAs are warmer but darker sounding, Sylvanias are more detailed but can be bright for some in certain situations and Tung Sol are somewhere in between. He offered reasonably priced used 6SN7 GTBs from the aforementioned three manufactures so that I can test them and compare. I would like to acknowledge Andy as he gave me a lot of appropriate advices.
After spending some time testing the three, I determined that RCAs did not match my taste. It sounded dull and not intriguing. Choosing between Sylvania and Tung Sol was harder and I vacillated between Sylvania GTB and Tung Sol GTB for a while using one for a few weeks then another for a few. What tipped Tung Sol off from my list was that in some recordings, timbre of string instruments did not sound right for me. They were not as accurate as I can hear using Sylvania. I do go to many classical and jazz concerts so accurate timbre of acoustic instruments is one of my critical attributes for audio that I strive to achieve in my stereo system. However, I was not yet convinced that Sylvania GTB is what I was looking for. So, my journey began.
I started trying different types of Sylvania 6SN7s. The list so far includes: GT, GT/VT-231, GT “Bad Boy”, GTA, GTB, cryogenically treated GTB and WGT. First I tried GT/VT-231 and WGT. Between the two, WGT provide the most details and high level of timbre accuracy so I stuck with WGT for a while. However, in my system, it sounded somewhat light and can sound bright and even harsh playing some recordings. Then I tried GTA which resulted in somewhat reduced a level of details but bit warmer sound with more body and weight. I felt it was a good compromise so it had become my reference 6SN7 for the past few years. I have nothing negative about GTs and GT “Bad Boy” but they did not leave me with strong enough impressions to prefer them over the others. Around this time, I tried Russian NOS military 6SN7 but quickly when back to Sylvania GTA.
In 2010, when I was still living in the Washington DC metro area, my audiophile friend from Japan came for a visit. So among other places, we went to Sophia Electric for a demo. There I saw their new 6SN7 tubes. I decided to try it since their amps were sounding wonderfully with these tubes and my friend whose day job was in the electronics R&D marveled how well made the tube was. It was indeed a wonderful sounding tube that added bit more weight and mid-range bloom to the Sylvania GTAs but with a small amount of loss of details and clarity. For the next year or so, I vacillated between the Sylvania GTA and Sophia Electric 6SN7.
As I had a good experience from the Sophia’s tube that is a current production 6SN7 from China, I ventured to try newly reissued Tung Sol branded Russian tube and the vintage Chinese military tubes both cryogenically treated. Unfortunately, I did not feel anything special about their sound. Most recently, in the summer of 2011, I tried cryogenically treated NOS Sylvania GTBs from tubeman.com. As soon as started playing the music, I knew my search for the “right“ 6SN7 is over, at least for now.