Black glass KenRad 6SN7s take the cake

Asa, I did not use the 231, I used the WGT version. And the sound difference was amazing. The observations made by others regarding the delicacy of detail, midrange liquidity, strong bottom end, crystal-clear high end were all there, far better than any other tube I've used in it. Now perhaps with preamps, where it is combined with other circuits, and passed through a power amp on the way to the speaker, there could be some "synergy" considerations that I didn't encounter on my system. The Berning MicroZOTL is the only amp ever to use a 6SN7 as an output triode, as far as I know, and it uses it in a push-pull arrangement with each 1/2 of the twin-triodes inside the single glass envelope performing the push-pull functions. Linearity is excellent with this configuration, and gives teriffic frequency extension on both ends, and of course, no output transformer to saturate or cause hysteresis problems. Now, as I stated, this is a different application of the tube, but I did not get as good overall sound from the Black Glass KenRad in my application, although it was very good sounding with them. The KenRad, Sylvania WGT, GTA and GTB, RCA Black Plate 5692, all were far superior to the stock Sovteks that came with the amp, and would all be a big improvement. I was more disappointed with the 5692 than anything, as it was well balanced, but did not have any real "twinkle" like these others had. And there is a definite difference between the Sylvania stuff, as the years went by. The older is decidedly better, and after the 1st couple of years of the GTB, it was a bad downhill slide. The 6SN7 W and WGT from the 40's are the best, and then the 50's, and then the early 60's chromedomes in the GTA version, and finally the early GTB. Later GTB were not nearly as good. I have not tried the very early metal-base version, although I have heard they are very good. I also did not try the Clear Glass KenRad. As they say, YMMV, and this is only my opinion.

Twl- Have never seen a "black base RCA 5692." The red base
RCA 5692s that were used in my MFA electronics(preamp & amp front end) had plenty detail.

Very interesed in your speaker system. Where can I get
details on the drivers and cabinets?

Aloha.

Kana813, I referred to Black Plate 5692, not black base, although there are black base RCA 5692 tubes. The Red Base 5692 is the famous "sought after" one, but there are non red ones also. Also the "Black Plates" are actually really deep charcoal grey.

My speakers are Voigt Pipes that use Lowther EX3 drivers. You can find info on the drivers here:

http://www.lowther-america.com/

And you can find Voigt Pipe plans here:

http://melhuish.org/audio/diy12.htm

The Voigt Pipe plans shown here are the same as what I used from the Lowther Club of Norway, but this guy used a Radio Shack speaker in his. It doesn't matter, the dimensions are exactly the same.
The Lowther Club of Norway has removed the plans from their site.
If you are going to make these you should contact me when you get ready to do it. I've been down the road.

The sound is awesome for low-power SET amps. Of course, the bass is quite sharply rolled off below 40Hz, but I don't miss that too much. Even the really good multi-way designs don't really go too much lower than that, in reality. Most are -3db at 32 or 28Hz. Unless you listen to alot of organ music, you'll never know it. The lowest note of a bass guitar is 41Hz, so if you mostly listen to popular music, its fine. That's only half an octave less bass in the least used area for music. The rest of the spectrum is spectacular, and the imaging is the best. Small sweet spot, due to directionality. Incredible dynamics and detail. Totally coherent. High end goes to 20kHz. Get the new series of drivers, as the previous upper midrange anomalies have been worked out. Don't buy a used pair over 6 months old. New is best. The EX3 will cost $895/pr and will give 100db with 1 watt input, when loaded into the Voigt Pipe cabinets. A 45 or 2A3 amp is plenty. A 300B is more than you need, but still sounds great. I ran them on 1 watt for 6 months with my MicroZOTL, but I felt I needed a little bit more headroom. My new Berning custom 45 amp will be here in a couple of weeks.

You can build the cabinets out of MDF for under $100. If you want fancy wood, you can do that too, but it costs more. I recommend that you at least make the front panels out of a good hardwood. It looks better, and it takes away a little harshness that the MDF has. I used oak fronts and MDF backs, and they look great and sound great. I also made a modification to mine that reduces the baffle-step effect under 380Hz. Due to the narrow cabinet design, the baffle reinforcement of the frequencies under 380Hz drops off due to wavelength. By adding some "swinging doors" to each side of the Pipe, you can bolster the mid-bass frequencies, and make the frequency response alot smoother in this area. Also, since they swing, you can tailor the backward angle on both sides to give adjustability to your midbass response, and tailor it to the music and to the room needs. If you need more info on this mod, email me for details. I have been living with these for about 6 months now, and I have no desire to look at any other speakers. These give me everything I need.

twl, I thought about "synergy" on pre input vs. amp output, but concluded that was a red herring because, theoretically, and in my gut, I feel the pass through on the berning should be best - or at least good enough for you to base a broad opinion on the tubes versus each other.

Haven't looked at my SylVT231's in a while, but I know they are NOS in army boxes with original packing from 1942, so assumed those were the good ones...

If your WGT are different, I am, of course, intrigued; always looking to learn something.

On the metal base, I never wanted to pony up, but a few who did with the Supratek thought they were not what everyone has said. Maybe the rep comes from pro guys, or the Glass Audio article a few years ago, but people's consistent reaction, coupled with the cost, made it easier for me to back away.

How about those black glass National Unions? Anyone try and compare those to the black glass KenRad VT231?