40+ watts SET, cost is not a problem

the listening distance is indeed near field (6-7 feet from the plane of the speakers). However, I do understand your point of these speakers needing a lot of power. Why do you suggest Class D and not A, AB ?

@pani Most solid state amps lack the Gain Bandwidth Product to support the feedback they have. As a result, at some point in the audio band (often, only 1KHz), the feedback begins to decrease on a 6dB/octave slope, often faster as frequency increases. Distortion thus rises on a complementary curve.

This sort of thing is audible, usually as harshness (since higher ordered harmonics are unmasked in this manner) and brightness (for the same reason).

OTOH its very easy to generate enormous Gain Bandwidth Product with a class D design. That makes it possible to have feedback with no rise in distortion anywhere in the audio band, much like a zero feedback amp but with lower distortion, which results in a more musical presentation with greater detail. Some class D amps, as a result, can sound every bit as musical and involving as the best SETs, with greater transparency.

’Nearfield’ is usually about 3-4 feet FWIW. If you really are limited to that distance you might find a tube amp that can do the job. The reason the Sensitivity spec (2.83 Volts/1 meter) is used is because solid state amps can double power as impedance is halved. Being able to do that defines the amp as a Voltage source and that is what the speaker is designed for. Tube amps can behave as a Voltage source too, but do it by cutting power in half as impedance is doubled. So tubes tend to be a lot more expensive on that account. Since tubes don’t double power as impedance is halved, the Efficiency spec (1 Watt/1 meter) is more useful with tubes because it tells you at a glance if you have enough power. 83dB in my room would require 800 Watts(!) and I really don’t know of anyone making an amp that is that powerful and also sounds like real music.

Consider that if you had a speaker of 93dB you would not need to take a hit on resolution or bandwidth, but the amp needed would be a 10th of the power. So you could do the same sound pressure with 80 Watts instead of 800 in my example just above. Now its easy. If nearfield you really could use an SET (although not to its best advantage).

Right now its simply out of the question. If you want to do your friend right, really think about a different speaker.

Having heard multiple Berning amps, they ultimately sound a bit sterile to me because of the switch mode power supply.

Its highly unlikely the switch mode supply has anything to do with what you heard! When you hear differences in amplifiers, again its the distortion of that amp that is its sonic signature. The SMPS is operating at 250KHz in that design; you’re not going to hear it. IOW I get that you might not like the sound of the amp but the SMPS isn’t why it sounds that way.

The biggest I know of are the NAT Audio Magma's.  Those things are monsters.

@paradisecom, yes, the Magma’s are monsters! The transformers are about twice as big as the ones on the NAT Audio Generators. The chassis is 26" long. The Magma M’s transformers are almost one foot tall!

The sonics are much more pleasing than the push/pull 805 Generators. Currently these high powered SET arms may offer the most value of high current/watts SET amps on the market.

My amp is a Shishido 805, which is the basis of the Wavac 805 (effectively the same).  I find it a truly stunning amp - I think there is an early review that pretty much sums it up.  What is wrong with it??  You would have to hear it, and then maybe you could figure out something wrong with it - I can't think of anything,  The amp is driving a pair of Altec 604 drivers in 9 cu ft cabinets.  Tons of power, and the amp has the drivers in a vice grip with regards to control and presentation.

The Wavac secret sauce is likely the Tango transformers, custom wound by extraordinarily skilled craftsmen in Japan for the Shishido design.  Hirata Tango for mine, ISO Tango and apparently Wavac for the later variants.  You can likely find response curves for the special transformers on the web - my book shows the output transformer flat from 30 to 40K Hz (0db down).  Also there is an interstage transformer, so no caps in the signal path.  A simple, yet highly competent amp using stunning parts.

Seems like nobody else has actually heard a higher power set amp like the Wavac, and yet they are fine saying they don't sound good, or it cannot be done.  Not sure how they feel comfortable doing that.  If you have a chance to hear one, then do so.  It might well change your perspective.

Pani, I powerful single ended tube amp design could work out fine but you will need to find the one that gives you the sound you’re looking for.  Some can be very musical and full sounding while others can be very neutral. Me and my friend both own different 45-50 watt single ended 805 tube type mono block amplifiers. Mine sounds very full, large and musical. His, very neutral and accurate. Mr and my friend have been into audio for 35 years. I own about 12 amps and he has probably about the same. We been through tons of stuff. I agree that a properly designed PP tube amplifier can sound absolutely fantastic. I have 3 amplifiers setup in my living room now in 3 different systems. A pair of VTL EL34 mono amps 178 watts triode modified. The single ended amp, a 805 tube working with a 300b tube to get 45 watts power.  And last amplifier is a CJ 100 watt PP EL34 amplifier.  I can honestly say, neither one of these amplifiers is better than the other. They are just different in what they do and how they present the music. I also own a Canary 300b amplifier that is wired with silver and do not hear anything negative about its sound. In fact, it sounds absolutely fabulous. My point is, I own a lot of stuff. Me and my buddy have owned ton of gear and still do.  I thought as you did about single ended designs, and yes, they can be excellent but so can other tube designs.