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Single Ended Triodes (SETs), the ultimate tube lovers dream.


Hi ! I am actually surprised you have not had the opportunity to audition real NOS USA 2.5V and 6.3V triode opt tubes, yet. Many lunar eclipses ago, I wondered as you do now. However, back in the eighties, there were no easily available Russian triode opt tubes stateside and most of the then available Chinese tubes were horrible. Reliability and sonics were not yet up to par. Having compared my used USA tubes to a friend's Russian 6B4 equivalents, I stuck with the USA tubes.

If I wanted a harder brighter sound, I used the unattached twin plates, previously known as the bi-plates. If I wanted a more natural sound, as I always prefer, I used the folded M or W plates, which I think many folks are now calling the bi-plates. If the plates touch and the plates appear like folded M or W, these are the most natural sounding to me. Regarding 2A3s, I usually prefer them over the Single Plate 2A3s. The single plate has unique qualities, but it is a harder sound in my PP amps.

Having already built 2A3 PP amps with ITs in the mid-80s, I then built some amps for the 6.3V and 7.5V tubes, using four pin sockets and high impedance opt trannies. That way, I could roll 6A3, 50, 10, VT-52 et al plus compare the sound with my 300Bs and then 252As (don't ask when and where they went)in my other SE amps. Also, having a few types of PP amps around the house, I could really compare and realize which to keep and which to flip. Well, I preferred the 6A3 as most natural, even in my 300B amps running at 5V fil ! Next preferred were the GLobe 250s and then the VT-52 tubes.

The 10 family was unique. I favored the tall plate globes and the non-gold grid varieties of tall plate STs. I actually despised the small plate ST 10s at that time, as they were way bright sounding in my amps. The Cunningham silver or black plate 210/310 were great tubes; bright sounding(and looking) but still here. Then, there were the white base 801s by RCA. These are keepers. Rugged, reliable and very nice sound. They are still available reasonably today. But, you know that.

I have a real opinion about the 2.5 vs. 6.3V tubes. Since the current is much higher on the 2.5V tubes, I believe the electrons flow more efficiently; maybe even faster. Call me crazy if you like. But, I have preferred to hear a 2A3 over a 6B4 or 6A3. Any of these win over the WE 300Bs for natural sound. Another great comparison is the 245 vs. the taller plate VT-52s. Yes; I want the 245s to stay. I still keep some VT52s around; but I sometimes wonder why. I also keep some large GL 10s as well as the RCA/Cunnings; but I rarely use them. The 801s are sufficient for me; but I only use them on occasion. When I do, I revert back to the 6A3; unless they are used in my late '20s Samson amp.

So, if I had to ditch some, and I still have many, I would move the 6B4s rather than the 6A3s. I like that four pin versatility. A strong 50 or 10 can run on 6.3V fil all day and night for many full moons. If you need octals, you will undoubtedly prefer the USA W or M plate 6B4s over the twin plate 6B4s and Russian or Chinese varieties. I have faith in your ears.

If you need some USA 6B4s, let me know. I could use the fair money. 6A3s I am reluctant to move; yet. Ditto with my quad of 250s. They have such a robust sound. I have the trannies to build a pair of Amertran 250 amps(as in Riders #1) and I suppose I will get around to that before I retire. But, for now, I am happy with my PP 245 amps. All DHT, 30-245-IT-245s. They have convinced me to move most of my 2A3 amps away. But, trying 45 STs usually disappoints me. I need my globes in my amps.

Since you seem to build or rebuild continuously, don't move out any tubes; yet. When you get to the point that you can reliably compare all the varieties within a small time frame, then you can convince yourself which stay and which go. But, comparing 2A3s with 6B4s or 6A3s is not as identical as you might think. Circuitry wise; yes. Sonically ? You have to decide, my friend. It is your listening happiness at stake...ENJOY !

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