2a3 ?

There are fans of the romantic sounding midrange of the 300b, who will not listen to anything else, while there are people like me, who like the tube, but not as much.  You simply must listen to a variety of amps using the various tube types to make up your own mind.  

All of these simple triodes are most often employed in single-ended amps, but they work well in pushpull; the sound is different for the two topologies.  Pushpull tends to have tighter, punchier bass and a better sense of drive, but, single ended amps tend to sound more natural, relaxed and less "mechanical" sounding (the bass punch of pushpull can sound the same all of the time, hence mechanical, while single ended amp bass seems more subtly variable).  I like both types of amps.  As I mentioned above my favorite is a very low-powered pushpull amp, but my all time favorite amps (that I don't own) include an output transformerless amp and an extremely vintage pushpull amp that runs a 252 tube (variant of a 300b).

I am a huge fan of the SET vs the push pull.  Push pull is your only option if your speakers are not sensitive enough but my speakers are and i've tried several different amps.  SET for the win.

Jerry

SETs have a limitation of the greater the power, the less bandwidth is obtained from the output transformer. 7 Watts (300b) is a practical upper limit to what can be considered 'hifi' bandwidth. The 2A3, being good for about 4 Watts, allows the designer to have a wider bandwidth and therefore less phase shift (which can be heard in how the sound stage is presented). The reason the type 45 has ascended the throne in the last 20 years is for this very same reason.

A pair of 2A3s in push pull can produce about 16 Watts, making for a more practical amount of power. If the circuit design is good, it will not cede anything to an SET; quite the reverse.

If you want a lusher sound from 2A3 invest in a pair of dual flat plate 2A3's.

Mine are branded Ken Rad with blackened glass from just above the flashing to the top (wide) edge of the tube.

NOS have a tendency to measure higher than most other 2A3's - like just above 80 on a TV-7D/U (my engraved base Visseaux 2A3's also measure about that).

DeKay

Good call Atmasphere. I owned the Melody i2a3

running 4x parallel 2a3's for 16-18 watts. A superbly

built amp (why did I sell it?). I have the speakers to

take advantage of five watts or less so no issues there.

I believe I understand single ended theory but doesn't True 

Class A single ended come from DHT tubes? Are amps

using el34, el84 and various KT's claiming single ended

actually pseudo single ended? I consider Wrights

2a3's true single ended whereas a Dennis Had

KT88 is pseudo? I've owned both but can obviously use

some schooling.