Interesting array of amps! I love the design and build quality of the 2 chassis design but have never heard the 46. The Korneff is an established design with a good reputation and I've heard one of these sounding real good, but in a totally un-realistic system and room (huge everything – modded A5s, horn sub, lecture hall where you could get back about 60' from the giant black boxes). Not getting the goofey old wood of the Yamamoto knock-off but have heard the Yamamoto 45 on several occasions and love/hated it – varied from incredibly good on the right speakers (think it was Lowthers) to real bad on others (Zu which I can't stand and Cain-and-Cains – just not enough power). If I had a store-bought 45 it would be a Yamamoto – can sound incredible and a beautiful piece of Japanese SET audio jewelry.
Some random thoughts beyond this;
For context – I use Altec 604-8Gs running full range in 9cuft vented boxes with 'helper' bass off a second set of pre-outs, 2x Altec 416A on an HK SS amp, digital crossover/EQ. My primary full-range amp on the 604s is a 2A3 SET (417A,cap coupled) but since this helper bass arrangement makes for lighter lifting on the main amp, I spend a LOT of time with this amp in 45 mode which I can switch to under-chassis. I LOVE 45s and these Altecs, but I happily live with 2A3s in this system.
First point; for me, as much as I love 45s, they do not cut-it on the Altecs (which are supposed to be around 100db/w/m sensitive) without the 'helper' bass stuff, and they are in a fairly small room. It's 'loud' enough, I usually listen at much less than 95db, but it's not about numbers on a sound meter – these speakers just don't show what they are capable of with 1.5w. Some types of music can sound absolutely sublime on the them with a 45, and it's massively seductive, to the point that you are often overlooking what they aren't doing. But kick up the dynamics & scale – areas that these speakers truly excel at on the right amp – and the 45 doesn't deliver, it's just VERY nice about it.
Use the right 45 tubes, coupling caps, speaker positioning, active pre-amp (have yet to hear a passive that I like in the areas of drive and dynamics), throw in 2x 15 woofer 'helpers' on big SS and tweak on the active x-over settings...and yeah, the 45 gets closer to Nirvana (damn I love the 45!) but, but,
Its still not there for all music, and I'm not talking about the difference between little girl with guitar and Dark Side Of the Moon only, you notice it a lot – you are right on the edge with 45/2A3 (1.5w/3w) and the 2A3 just gives you more presence, snap, body and tone, that sense of ease and scale around big dynamic swings that 1.5w just doesn't do on these speakers. It's easier to forget about all the stuff in the room and get lost with the 2A3, the 45 often has you thinking damn, this is great, but, but, what about that big bubble of goodness that this recording usually puts in the room, where's the big space & dynamics? What happened to the 'Altec' in the Altecs?
All VERY personal but 2A3 is a better place for me on these 100db sensitive speakers, just makes all the right compromises (and there are a lot of compromises in this SET/Hi-Eff thing). 45 is pretty damn special and for some types of music, it's the best I have, but it's no daily driver. (I have an old Lotus under a blanket that I can't live with 99% of the time either
). Listen to Muddy Waters' Folk Singer or a small venue acoustic Jazz recording and the 45 is the shit, spin some Stevie-Ray, big female vocals Jazz in a larger club (say Carmen McRae) or even Neil Young in a place like Massey Hall – back to 2A3...fast!
I also like David's suggestion of the Almarro EL84 amp – that thing (thanks for the time with it Ernie!) surprised the hell out of me – got real close to the 2A3 and I could happily live with it, especially over a 45. Really makes me wonder what is possible in that vein (say no level pot, no or less negative feedback, tube rectified...I'll stop now).
My audio re-birth a couple decades ago was all about 'Less is More' but I started with speakers that spoke to me and built around them, and 'Less is More' with Altec 604s for me, starts around 3w. There are LOTS of options out there from 3w up.
