Tube rolling in Hagerman Trumpet MC

@lewm@chickenoregg

I've enjoyed the read of this very much. My favorite combination of 6sn7 tubes yet in my Cary SLP 98 F1, has been RCA gray glass VT231 in the buffer sockets and Kenrad Black Glass VT231's in the line stage sockets. In my set up, I do not find either to be microphonic. I have many of the others that got mentioned, except the ridiculous money ones. I have bought exclusively off of Ebay, from sellers with the best FB ratings and have had very little trouble. I have had a few tubes that may have been damaged in shipping, causing a short or dead on one side, etc. and have gotten my money back all except for once. I agree with @chickenoregg about used tubes, 90% of what I have bought were used but with very good test results.as to balance etc.  They are broken in so you don't need to listen for 100 hours or so to evaluate them. I've also had NOS, which is nice but take a good while to fully evaluate them. 

As any tube users  should and usually do note, each system is different and what is my favorite may not be someone else's. That said, the most popular tubes earn that popularity by pleasing a lot of listeners in a lot of different systems. That is why all these threads have value. Of newer tubes, I can't say too much bad about the EH Gold Pin 6sn7 tubes. They are Russian made and had only 10 hours on them when I got them so had a lot of time, breaking them in at first.. I tried them in both positions, as they were all I had at first (other pair was the steel pin EH), came with the Cary. They were not bad in the gain stage (gold pins) but I do like the vintage ones better. In the buffer spot, I could live with them if they were all I could find or all I had. I probably have well over 100 6sn7 tubes and enjoy trying different combinations. It is likely that I will still buy more and keep trying new combos. I'm old and easily entertained. :)

"Buffer" is usually another term for "cathode follower" in tube gear.  The CF has unity or less than unity gain, so any tendency toward microphonics is minimal. Usually, microphonics are a problem with gain stages. My private theory is that microphonics can sometimes add to verisimilitude in listening, in a beneficial way. And that all triodes are microphonic to some degree, but the octal based dual section triodes are worst of all because of the large area of glass envelope and maybe because of some instability of the structure within.  But when the tube really takes off and starts ringing, it is unbearable.

@lewm Yes, I thought it made some sense that the buffer stage would have less impact than the gain stage and less consequence of a microphonic tube. I found that very difference in the EH Gold Pins when I used them in each position. 

In my set up, I find the 6SN7's to be very quiet tubes, in that even at a very high volume, there is no audible tube rush. The opposite is true in my Cary phone preamp, which uses 12AX and 12AU7's or their variants. There is very notable tube rush at higher volume until the music starts, then it is inaudible. I believe it is a different design than the SLP 98, as I've read that all gain is from the tubes. Maybe that means that something else provides at least some of the gain in the 98 preamp. I don't really understand all this but I don't have to either. I don't plan to build or even rebuild these components. I trust the manufacturers to that. 

In the old Cary PH301 phono stage, it came with some very cheap Chinese and Yugoslavian tubes. I described them as "ringy". Even with them, I could tell that the Cary was a step up from the old phono stages that I had used before. I also had recently switched to LOMC from MM and I know that made a difference as well but got hooked on tubes in pre stages in this way. My humble beginnings. :)

I get that the 6SN7 has the larger glass surface but what about the really large tubes like KT88's (I think that's what they are). Seems a lot of folks are in love with them and the old 300B amps?????????? I"d love to hear them sometime but probably never will. Anyway, sorry to gab so much. This stuff is all very interesting to me, at least from a listener's standpoint. 

@lewm 

Thanks for all of the information and conversation.  I have stayed out of it by and large because my system is much more humble.  I just can’t resist though.

My favorite 6sn7 variant is the Melz metal base 7 hole plate version 6n8s from the early 60’s.  When I bought mine, they hadn’t been discovered yet, so they were comparatively cheap.  I have two pair and a pair of Sylvania black base VT231 as well.  The 6sl7’s are the old red/brown base Brimars GTY version, rectifiers are Mullard 5ar4.  And the 300B pair are Takatsuki though I have a pair of EML mesh plate as well.  It is probably obvious that this is a low watt SET system (8 wpc).

I don’t even remember all of the preamp tubes I rolled through, it has been about two decades.  I know various RCA, and possibly some Sylvania or maybe Westinghouse?  
 

The most unusual find were the USSR tubes, I didn’t expect them to be that good, but they seem to balance out the warmth of my set up and add some speed and extension.  I don’t like terms like “air” or “sparkle” but there you have it.  I could see where they would be way too bright or edgy I a different system.

Oh and btw.  No issues with microphonic in the preamp.  Just the phono stage.  The ax7’s can really take off in the initial gain stage pre riaa.  That running is pretty amazing to experience.  My favorites I. The v1 of the trumpet mc are a pair of Siemens Ecc83 with 19mm plates, they are microphonic somewhat, and just wonderful.  I did find out about a trick that while a bit risky is worth a try.  It did help for noise and actually the tubes are less microphonic as well.  Take the tubes and holding them firmly, rap them on a table a few times on their sides.  Then turn them upright and more gently tap them on the table, or use a pencil to tap the side of the tube. The theory is that at times a bit of the plate coating (or other material) can dislodge and get stuck in the grid area and this let that fall to the bottom of the tube where it is less likely to cause a problem.  It worked and I can still use my favorite tubes.  Most of you probably knew this, but I thought I would share it for those who don’t.