300b lovers

The difference is Class D switches at 100 kHz or higher, with pulse width translating to signal level, while Class A is non-switching and like a preamp, fully analog from start to finish.

@lynn_olson most quality class D amps switch at 500KHz or more. Also to be absolutely clear, class D is 'like a preamp, fully analog from start to finish.' A very different type of circuit, but analog nonetheless. 

I do not have the resources to confirm this via test bench measurements as you do. I can only rely upon listening experiences with my own audio system.

@charles1dad Lynn is correct- if you are not running feedback then everything in the amplifier design right down to the component quality, wire and solder makes a difference. When you run lots of feedback you get rejection of things like that- often including sensitivity to line voltage.

That’s why I am agreeing with what Lynn wrote. Zero NFB seems to uncover a masking effect. The subtleties and nuance of virtually everything is revealed as noted.

Charles

Zero NFB seems to uncover a masking effect.

@charles1dad That's not quite correct. It depends on how well the feedback is executed and as I've been pointing out a lot recently, with most amps made in the last 70 years or more that's not happened.

But if its done correctly, amps using it can be amazing- no hint of dryness, nice soundstage; everything you want in an amp.

I've described what's needed often enough, no need to repeat it here.

Ralph,

I understand that you are referring to the approach you use with judicious application of negative feedback. I was referring to Lynn’s comparison to the “golden age “ PP amplifier which typically used 20db of NFB. Your current class D amplifiers do not fit this description.

Charles

Gents,

I have had several Class D amps in my system in the past 10 years, and the earlier versions of them were dry and lifeless after extended listening sessions.  In the last couple of years, I had the VTV Audio EVO 1200 Class D amp with the Purifi module, with the aftermarket ministrations of Ric Schultz, and while the sound was as Ralph describes it, there was something missing in the sound after extended listening sessions.  It may clearly be due for my inherent biases, I will readily admit that.  After listening to the VTV amp for few months, I swapped back into the rack my McCormick DNA .05 which had their Platinum upgrades and after a few minutes of listening to it, I said to myself... "Ah, what was missing with the VTV amp has all been restored."  That is what I experienced, plain as day. I later got the stellar Wells Audio Innamorata SS amp, lovely both in its looks and more importantly in its sonic excellence -- easily the best SS amp I have ever had in my system.  After a few months of enjoying the Wells amp, I swapped Don's KT88 tube amp back in the rack and it was easy to hear the difference in SQ... back was the liquid sound of tubes with amazing extension on both ends and a soundstage that mesmerized my ears.  None of the sluggishness in sound of my old CJ gear, which was appealing to my ears, but far from an accurate sound reproduction, so Don's KT88 amp had all the advantages of a SS amp but had the warmth, richness and liquid sound that I desire which serves to envelope me in the listening experience (which I agree my VTV amp did to a degree initially) but here is the difference:  after hours and hours of listening, I loved even more the sound for the KT88 amp, whereas in extended listening sessions, there was a lacuna in the sound with the VTV amp that I clearly sensed and missed.  

That said, my new 300b monos are a quantum leap forward in SQ even compared to Don's KT88 amp in all respects and most noticeably this:  it sounds as if there is no amp at all... just glorious music enveloping the room, with pure tonal and timbre correctness that astonishes me... and absolutely dead quiet.  As good as the Kootenai is, and it is a stunning and powerful 65wpc tube amp, the 300b monos are in a whole different realm. 

I have not heard the fairly-price AtmaSphere Class D mono's at any audio show, but as Ralph has come from a tube-centric point of view, I must acknowledge that he might have be on to something with his design, surely he is. There are lots of advantages to using a Class D amp and God bless those that love them.  

This erudite conversion with Lynn, Don and others has been a deep dive into tube design philosophy and I personally am hearing the splendor of their creation moment by moment, lucky me, for darn sure.  Again, and not to be disputatious on this wonderful thread, for the liquid euphonic and most natural presentation musical reproduction with my new 300b monos, I am still firmly in the tube amplification realm as it recreates music in such a realistic way, so pleasing to my ears.  The hell with the heat the 300b monos throw off!

Now, with another 100 hours on the amps, I will amplify the comments I made in my OP--- these amps are the most stunning addition to my 50 year quest for more accurate and pleasant sound in my system.

I am driving my 86db efficient CSS Audio Criton 1TD-X speakers with the 300b amps at the moment and I can play music as loud as I can possibly tolerate it with no sense of distortion or clipping.  I have a 8 wpc Willsenton 300b integrated amp which I drove the same speakers with and it got pretty distorted as I rotated the volume knob to the right.  I recall that Don said that his mono's sounds "like a 100 wpc amplifier" and he is exactly right.

Boys, you are going to have to pay to play with Don/Lynn's new monos, but it is clear to my ears that if you are looking for an end game in amplification... and have the appropriate synergy with your speakers, then I hope you get a chance to hear them, which I will in the Spatial Audio room at the Pacific Audio Fest this month in Seattle, along with Don's new companion tube preamp.  

I have a pair of Cube Audio Jazzon single-driver speakers arriving on Monday which I think will be a stellar match for the 300b monos, but still the the mono's have made my Spatial Audio Triode Masters sound the best they have ever sounded, by far.  To be candid, if I had had the new 300b monos, driving my Triode Masters, before I ordered the Cube Audio speakers, I don't think I would have ordered them so as the Triode Masters sound so fantastic.  Don Sachs encouraged me to buy them ~6 years ago and now he has as his reference speakers the Spatial X- speakers, clearly an upgrade from my Triode Masters.

I live in Sacramento and would be happy to invite music lovers to come and hear my Don Sachs gear and my Cube Audio speakers.  Send me a private message and let's hear them together.    Cheers!