2a3 ?

When my local Audio Note desler first set up the ultra expensive AN-E SEC, he chose Audio Note’s Kageki (parallel SET 2a3 amp).  He used the same amp when setting up the top AN-J model.  The sound of both speakers was magnificent.

i own the Kageki and like it, although these days I run my pushpull 349 amp.

Very much looking forward to reading people’s experiences. I recently picked up a Sony TC500a R2R portable player. Bought it to harvest the transformers and the speaker drivers. 
 

Trying to figure out if I want to build a 1626, 45 or 2A3 with the transformers. 
 

leaning towards the 2A3/45 option. 
 

I love the 2a3 tube I have a pair of George Wright monos myself and love them. Clean and clear sounding but still natural and warm they drive my Audio Note AN-J's perfectly.

Nearly pulled the trigger on 45 amps as well but concerned

about availability/durability/reliability of tubes that haven't been manufactured in decades. I have little tolerance for equipment that

may have questionable reliability.

I have been told by someone who should know that a 2a3 is, essentially, two 45s in one enclosure. When I used to own a 300B amp I was always a bit puzzled about the reverence shown to the 2a3. I wondered why praise of the 300B was not universal? Why was it often considered as "behind" the 2a3 and the 45?

Then I got to hear the 45. The midrange emphasis of the 300B was clear, as was the more extended frequency response of the 45. The tone and inner detail of the 45 was breathtaking (my room, my speakers, my listening preferences, YMMV). 

So, not exactly a response to the OPs original question, but I wanted to add my .02...

I have heard some SET amps running the big transmitter tubes, including a 1610 tube, and I have not heard any that surpassed the lower powered SETs when playing speakers of high enough efficiency such that no amp was being forced to play out of their comfort zone.  Yes, some 211, 845, 833 amps sound pretty good, but I still like the 45, 2a3, 300b amps a bit more.  

I never ran my parallel SET 2a3 amp into hard clipping, but, I did suspect it was slightly compressing peak volume when playing certain kinds of music.  This appeared when playing large acapella choral works at somewhat high volume--no obvious distortion but the music sort of stopped getting louder at peaks (99 db/w speakers).

I don't agree that, even with very efficient speakers, SET amps always win over pushpull.  There are certain pushpull amps that deliver the same sort of natural, harmonically dense and complete sound of good SETs, while sounding a bit more punchy and dynamic.  There are also contenders from a completely different camp--the output transformerless (OTL) amplifier.  The incredible dynamics and liveliness of good OTL amps can be extremely captivating, and they deliver this kind of sound without necessarily being bright or harsh.  I don't think any particular topology beats another; it is a matter of taste/priorities, system matching, and specific execution of the topology.

Loving my Whammerdyne DGA1 amp pushing out just over 4 watts per side, with ultra wide bandwidth transformers (14 Hz - 50k Hz +/- 3 dB). If you are near Atlanta, GA, you are welcome to stop by for a listen.

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.

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

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.

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

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 own the Coincident 300b stereo and am very happy and impressed with it. I did upgrade the tubes on my own.

I had a wonderful Tektron amp that used 45, 2A3, and 300b.  I think the 2A3 might have been best but it depended a lot on the tubes.  Jerry

My speakers are 99 db/w efficient.  I own a pushpull 45 amplifier that works well with these speakers, but, I don’t play music that loud so I can’t say how happy others would be with my setup.  I have a parallel single ended 2a3 amp that also delivers sufficient power.  My favorite amp is a pushpull 349 (this is a very rare tube that, fortunately, has a long life when driven gently) amp that delivers about 5.5 wpc.  

I have both! A Will Vincent custom- built 45 SET using Emcron output trannies; a 2A3 Sanei 560A with Tango power, choke and trannies from Japan. Neither in use because I sold my vintage Heresy's - the only speakers on hand capable of use with low power SET's. The 45 is only good for 1.75 watts at clipping; the 2A3 will do 3.5 watts. Subjective impressions of these two tubes is entirely dependent upon speaker choices. In fact the 45, 2A3 and 300B are most linear when used at 25% power. Past that distortion rises rapidly!

I like 2a3’s, provided the speaker is efficient enough.  The. 300b tends to deliver a richer sounding midrange and a warm bump in the upper bass that is part of the “magic” of that tube, but, compared to the 2a3, the 300b sounds murky and not as dynamic and alive.
At even lower power, there is the 45, which sort of fits between the two.  It is not as lean sounding as the 2a3, it delivers deep bass (but tighter and punchier than the 300b), good dynamics, and almost as much clarity as the 2a3.