Tube rolling in Hagerman Trumpet MC

@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.

Lastly if anyone has thoughts about “better” 6sn7 or 6sl7 that aren’t crazy expensive, I would love to hear about them.

For those of you who feed your Hagerman Trumpet with an SBooster power supply, what voltage do you use? Thanks for the help.

My most recent experience if Tube Rolling 6SN7 using the KR VT231 Black Glass, as the tube to be compared to as the Base Tube, ended with a unexpected outcome.

In my circuit, two Valves from different Brands, but similar production era's to the KR, showed the KR's as having a artificial bloated bass and not competitive in any way the Bass that was on offer from the other two Valves. The KR fell way short in being able to create the impression the other two Valves were capable of in the Mid's and Highs.

A stated in my circuit on my Power Amp's.