"Warm Sounding" Solid State Amplifiers

^Also, though Nelson Pass was still there, the "T" series amp(s) that your brother had, were from the pen of Mikael Bladiliaus, Jaynes and Coburn.

Try the Luxman Class A amps. The 550AX and 590AX are awesome sounding, tube like SS amps. Not sure what your music likes are but these may not be good for loud hard rock. The 550 goes for $4,900 US and the 590 jumps to around $9,000.

Not sure where you are located in Canada,but the are many retailers who carry this brand in the "Great White North"!

Thanks again folks. The Threshold amps appear to show up at a lower price points on the used markets. Seems worth while to check out! If I'm lucky I might find a seller in Southern Ontario. There's one for sale in Alberta but freighting heavy and expensive things across Canada is somewhat of a costly hassle.

As for Luxman amps I tend to see a lot of the more vintage models for sale.

Csontos, thank-you for your reasoned reply. I thought you might like to hear a number: 600, as in 600V/uS, the risetime of the output section of our amps. Tubes don't have to be slow nor dull any leading edge transients.

I agree with Mapman- there is something that is neutral, neither bright nor dull. The thing is, when audiophiles talk about bright or dull it is rarely about actual frequency response errors. The brain translates distortion into tonality. This is why single-ended circuits (tube or solid state) tend to sound 'warm'; its not a frequency response error, its the brain translating a 2nd ordered harmonic into tonality.

Our ears use the higher orders, 5th and above, as loudness cues- the brain uses these harmonics to calculate how loud a sound is and does not rely on the fundamental tone for that. As a result, our ears are more sensitive to these harmonics than the best test equipment- we can easily hear these harmonics as distortion where its difficult to measure.

This is why two amps on the bench might have the same bandwidth, but one might be bright (has a trace of higher ordered harmonic distortion) while the other does not. In addition, the ear/brain system while translating higher ordered harmonics into brightness, also translates the same into harshness.

Its my stipulation that it does not matter whether the amp is solid state or tube so long as these harmonics are not added by that amplifier. IMO/IME the best systems have a sense of ease at any volume and there is never the quality of 'loud' no matter how loud its actually playing. This BTW is a property of real music.

Sunn made some guitar amplifiers that were solid state back in the 1970s. Now if anyone here plays guitar and uses an amplifier, they know that most guitar amplifiers are vacuum tube, on account of if you want to overdrive (distort) them, you need tubes to have them still sound like music. But Sunn made solid state amps that at the time and to this day were recognized for having a 'warm' sound to them. When you look at the schematic its obvious why: the preamp section employed FETs in a single-ended topology with zero feedback (the FETs being very linear did not need feedback; the primary distortion product being the 2nd harmonic), and the power amp section was also single-ended until converted to push-pull by a driver transformer. So the power amp was rich in 2nd orders as well.

Now I am of the opinion that the 2nd order that is traditionally associated with tubes does not have to be there. That is why we make our amps fully differential and balanced; even orders are canceled not just in the output section but at every stage inside the amp. So while they sound smooth and are detailed and fast, they don't have the warmth associated with a lot of tube amps. The take-away is that topology plays a bigger role.

The Sunn amplifiers are considered obsolete designs, but if you really want warmth as a sonic attribute finding an amplifier of that type (or building one) might be a consideration.

Ralph, can you describe live unamplified without reference to amplified? Where does 'warm' come from in reference to unamplified? To me, the 'holy grail' is 0 distortion. With that comes perfect neutrality vis-a-vis, 'live', no? Ime, non detectible IMD/TIM results in the intended goal when the FR is truly flat. I truly believe this is what we're all looking for whether we know it or not. It's the jargon that gets in the way of arriving at a real understanding of what constitutes live sound in an amp.

What are the loudness cues our brains use for natural, unamplified sound, or a tube amp? Without higher order harmonics, what do we use?

When you describe "bright" sounding amps, are you comparing to other amps, ie: tube, fet, etc.? Or are you using live unamplified sound as your reference? More often than not the comparisons I read are tube vs. ss.

I think live as an established reference for both tube and ss reveals the only truly accurate yard stick in ranking the performance of an amp.

Both fall short, some deliberately(usually tubed),some not(usually ss).

What you appear to be making very clear is that distortion is the arbiter in judging neutrality. So other than utility, tubes are not necessarily required to achieve the desired goal. And I don't want to beat you up on this but if I may digress, you did use the term 'warm' in reference to live unamplified sound.

Having said all that, I suppose my next question would be, 'typically, how flat is the FR of one of your amps? I mean if you stretched the tape out to 5 feet.

The most notable difference I've experienced among the amps I've owned and still own, is that character you touched on regarding volume. I have only two amps, both ss, that have that quality of high volume without fatigue. This is mine, and I believe everyone else's natural yardstick to recognizing life-like sound and coincidentally, noticeable distortion.

And this is the crux of the situation as they say. It now becomes quite obvious that for the most part, you by default, are correct in that very few ss amps with that characteristic exist. All those apparently 'warm' ss amps are going to hurt just as much as any other low distortion ss amp when cranked.

However, it didn't take $100,000.00 for me to acquire that quality. But it did take time/research. Interestingly enough, my favorite LSR&D amps are also obsolete. I think it serves to point out that these amps are the late Dr. Marshall Leach's famed LOW TIM design. They can still be had as diy projects. Also, this design has been incorporated into some other brands such as Heathkit(vintage), some Crest(sound reinforcement), HK 990, to name a few. The other is my Boothroyd Stewart Meridian 105 monos. The Brits have a pretty good handle on what we're talking about here imo.

Also, I think the famous Bob Carver Challenge has a place in this discussion. Still not sure if Mr. Carver is in a league by himself. On the one hand ostracized for having the ability to mimic the sound of any amp, ss or tubed without having to copy the circuit, and on the other, celebrated for his sonic achievements. He's clearly shown that neutrality is a matter of circuit design and that the question of tubes or ss does not enter into it.

I still wish I would have scooped that S-30 before it was too late, though:)