Tube rolling in Hagerman Trumpet MC

@pryso ,

I would say, if you're happy with it, just leave it. My only thing is that if you're planning on upgrading the unit, I would do the power supply over replacing all those tubes any day of the week.

@lewm 

I love 6SN7. But in a way I love 12SN7 more because they are one of the best values out there —you get the sound of your favorite 6SN7 at a fraction of the price. The GEC B36 vs. B65 is a great example. Metal based pairs of GEC/Osram/Marconi B65 are listing regularly (and selling) on ebay for $4,000/matched pair. I saw a pair for $4,500 even recently. You can buy the exact same metal based tubes with the only difference being the filament voltage for around $600 — often new in the box.

The LTA Aero DAC is brilliant because it lets you toggle between running it’s board at 6.3v vs 12.6v. I wish more gear offered this, people don’t seem to be aware of the enormous value of that feature.

Were the Ken Rads you had VT-231? The mil spec VT231 are different in construction and sonics than the civilian ones. The VT231 has flat but staggered plates vs. the civilian tubes which are 1:1 opposed from each other. The VT231 sounds better. I think the VT231 also has more construction differences related to the preventing microphonics. The clear and black glass tubes actually share the same sonics, but people always prefer and want the black glass tubes making the clear glass VT231’ s cheaper and a great value.

One of my favorite 6SN7 of all tie is the National Union Tall bottle full dark grey glass with round plates. They are distinguishable from others because they look very similar to the Tung Sol Round plate when looking down at the top of the tube. I I rarely see these, in fact I had to hunt down the last pair I bought and regrettably sold to a client one day when I got too excited about them.

I also like many of the Sylvania tubes. The 1951-1953 tall bottle 3-hole T-Plate tubes are just excellent. As are the 6SN7W tubes. Nicely musical.

The Raytheon VT-231 are an excellent tube if you want more neutral/clean.

Best I’ve heard though are Telefunken 6SN7GTA and GEC/Osram B65.

I spent last night making some homemade 6F8G to 6SN7 adapters so i can try running four 6F8G in place of the four 6SN7 in my VAC 200IQ.

Rockets,

b

Currently rolling with Amprex Globe 12ax7's in first position, 5751 RCA's in slot 2 and RAM 12au7's in the 3rd spot. Sounds nice and natural and very 3d.

I may look into the SBooster down the road.

db

As regards the 12SN7, I use 12SX7s (milspec versions of 12SN7) as driver tubes in my Atma-sphere amplifiers. The power transformers in the amplifiers can be wired to produce either 6V or 12V filament voltages. I have tried all of the 6SN7s you mention in the MP1 except maybe the 6SN7W.  The RCAs are perhaps a tad better than the Brimars but also, like the KenRads, very microphonic. None of the others floated my boat.  I think we have to be careful about drawing conclusions on how a tube sounds based on listening to it in only one piece of gear, since bias voltage, plate current, and plate voltage all play a huge roll in determining tube function over all.  Some circuits are just badly conceived. And this is one important reason why there is so much controversy about what tubes sound best.

When I mentioned "RCAs" in reference to 6SN7s, I specifically mean RCA 6SN7GT or VT231 with gray glass.  Those are excellent but again were too microphonic to tolerate in the MP1. (Could be they would be fine in some other chassis.). I've got a mint pair of those just sitting around along with a bunch of KenRads.