Don Garber's Fi X is also there!!!
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A 2A3 is a true triode.The EL84 is a pentode that they will wire up to run similar to a triode.I would lean toward a true triode to get the full benefit of one.That is with everything else being equal.In other words a better made EL84 can sound better than a poor 2A3 amp.The Antique Sound Lab "Tulip"is a decent sounding 2A3 amp.They've been making it for several years and keep raising the prices.Years ago they were $1000,now they want $1500 for a new one.I've heard people buy used ones in the past for $400.I don't know what one could be bought for now.It puts out about 3 watts real triode.
Putting together a 2a3 based system can become a very expensive proposition especially if you are not into DIY speakers. You will need very sensitive speaker with a benigh impedance which will necessitaste very low noise tubes and associated equipment. 2a3 ET based systems can be very frustrating if not done right, but also very rewarding when everything comes together.
I don't know of even a Bottlehead kit that falls in your price range. While SET amps are "simple" in design, they are never really that cheap to make, primarily because SET topology puts extreme demands on the output transformer. The transformer is a very expensive part.
Is there a reason you mentioned the 2a3 tube? Of the three most common directly heated triodes (2a3, 45 and 300B) used in SET amps, I think the 2a3 is the leanest sounding (tight, but thin sounding upper bass) and would not be my choice for "sweet" and "easy to listen to." What I like about the 2a3 is its clarity and wide open top end. I like the sound of 2a3s (my main amp is a parallel 2a3 SET, but, it would not be my choice in a lean sounding system. The 300B is probably the warmest of the three types I mentioned, and has the highest output, but the tube itself can be pretty expensive. I really like the sound of 45 tubes (tight, but fuller bass than the 2a3, not as rich in the lower midrange as the 300B), but they have the lowest output of the three. Higher powered directly heated triodes include the 845 and 211 tubes, but with these, the tubes are expensive and the higher voltage power supply means more expensive parts and more care is needed in construction (potentially fatal voltages involved).
I have heard the Bottlehead monobloc 300B amp. It is a decent amp, not too expensive, and easy to build, but, I think it is more than double the price range you mentioned.
Another consideration is the 2A3 version of Dignity Audio's amplifiers. They can be used with or without a preamp. If you're anywhere near Brooklyn NY they're definitely worth a listen. Alan at TAS Audio builds the speakers he demos with the different SET varieties that they sell. He uses the same drivers I have seen in the big name brands but tunes the crossovers accordingly. Very musically involving & amazing sound quality for a relatively inexpensive system. I visited the store for 2 years before finally purchasing a pair of the 300B amps. I kept trying to match the sound quality at home with my more expensive stuff & was unsuccessful. I'm pretty happy now & put some money back in my pocket too.
Larry: Thanks for the info on what to expect from various tubes. I want a 3-4 piece bedroom system with small fostex DIY monitors + powered subs or 4 ft folded horn, but for now I'll start with a pair of KEFs w94 db sensitivity currently in my bedroom, maybe I'll get lucky with them). Bedroom is 25 x 20 x 12. NO TURNTABLE!!!. An Agon member is selling a pair of built upgraded Bottlehead 2a3 monoblocks for 750 which started me thinking. My instinct says go with Dared or Almarro and not a kit in the same price range if things don't work out or I can put it somewhere else where I have more room and do a SET system properly. I have drawers full of 6SN7, 12AT AX AU and rectifiers from other systems and this can get frustrating at times but I have no listening experience with SET equipment, but, tubes are the way to go. So far no easy answers, but thanks for all the food for thought.