Again the topic of weight of amps

Encouraging the OP to not at least give a good class D amp a free in-home audition for a month is just willful ignorance, akin to encouraging not hiring the most intelligent and competent black job applicant because of their skin color.

Well, I read it, but I refuse to believe that I read it.

@noble100
I will do my best to respond to your questions.

I think you had the Acoustic Image Atsahs using Hypex NCore 1200 power modules if I recall correctly. I think you liked the idea of their small size, light weight, low heat and being so efficient you could leave them on 24/7. You thought they sounded very good but thought your class A Clayton M-300 mono-blocks sounded better.

You are exactly correct. I can add that at the time I also owned Lamm M1.2 Reference monos and an SMc Audio Signature DNA-2 LAE stereo amplifier and after a lengthy comparison I decided that I liked all three better than the Atsahs. I mentioned the Mono & Stereo review of the Kalugas because they use the same NC1200 amplifier board (with some modifications to the PS and a few other internal do-dads) and the reviewer does a good job of describing what I heard with the Atsahs. If I had liked the Atsahs, I certainly would have kept them and if I thought I could correct the issues I had with those amps by buying Kalugas or even Theta’s Promeatheus (NC1200 with linear PS) then I would have already done that.

You consider the bass from the class A Claytons more natural and better refined since they didn’t have this truncated quality. I think I understand your meaning of truncated bass, which is bass that lacks the natural decay of deep bass tones when heard live. Please let me know if I’m correct.

Yes - correct, plus the high damping seemed to take away from the fullness and bloom I hear from live music. The Claytons have those qualities plus well-defined bass that make it possible to distinguish the different instruments providing the bass (i.e., not one-note bass).

I’ve also been trying to determine why you perceive this truncated bass quality on your class D amps but I don’t on my D-Sonic M3-600-M mono-blocks. I know my amps are very good but, having only read reviews on the performance of the Atsahs and Kalugas, I believe it’s safe to rule out the very slim to no possibility that my amps outperform either of those.

I long ago gave up prescribing what is "good," "better," or "best," based on what I read, marketing hype, and/or what something costs. Bruno did an excellent job of marketing his modules as being the "best" and was able to charge many times more than the going rate for Class D modules based on a combination of marketing and some good reviews. Some things I have been interested in following are whether most of the early NC1200 adopters still own their amplifiers and why those amplifiers (i.e., Kalugas) never achieved their promise as standard-bearers for amplification, regardless of class.

I’ve thought of a few alternative possibilities that may also explain our class D bass perception discrepancy that I’d like your thoughts on:

1. The music we play. I mainly listen to electronic and acoustic rock, blues and jazz and very little classical music. I don’t know the typical types of music you listen to.

Rock, acoustic rock, some popular, and blues with a touch of jazz but no classical - similar to you.

2. The speakers we use. I use large 6’x 2’ 3-way Magnepan 2.7QR dipole planar-magnetic panel speakers that each have a 625 square inch bass section that produces very accurate, detailed and ’fast’ bass response. The combination of my class D amps having damping factors >1,000, and outputting 1,200 watts each into the 4 ohm Magnepans, resulted in the best bass performance I’d ever heard from these speakers.

Aerial LR5s which are acoustic suspension (sealed box) speakers with dual 9-inch woofers per side. They are excellent down to about 40 Hz, below which I augment with two Aerial SW-12 subs adding only the very low bass below 40-45 Hz.

I added an Audio Kinesis Swarm bass system. Here’s a link to an Absolute Sound review that describes its effects on my system and 23’ x16’ room very well:

https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/

IMO, the Swarm system may indeed be the reason you like your bass so well and I certainly believe it probably sounds excellent. The bass in my room improved significantly when I added the second sub and switched from the bass reflex Aerial Model 9s (which sometimes added too much and too boomy bass) to the more accurate sounding acoustic suspension LR5s. I like Duke’s concept for the Swarm and would like to try adding one, if not two, more SW-12s in my room.

My current conclusion is that the reason your perception that the class D amps you auditioned in your system truncated the bass and I did not perceive the same bass truncation is likely due to one or more of the following causes:

1. I spent a limited amount of time listening to purely class D bass reproduced solely on my main speakers since I fairly quickly added the four sub Swarm bass system which is actually class AB bass reproduced mainly on conventional cone subs that do not tend to truncate the bass.

I suspect this is the reason.

Now you’re having new amps built with custom Plitron toroidal transformers? Can you give more specifics on the new amps being built and your speakers?

I discussed my speakers above and the new amplifiers will be SMc Audio DNA-1 Signature monos using new boards and other very recent improvements Steve and Patrick have incorporated into their design. The amplifiers will be almost a complete rebuild with mostly all new parts, new grounding concept, high-quality Lundahl transformers, and other proprietary improvements. As good as the other amplifiers I have owned sounded (including the excellent Claytons and Lamms) I have wanted to merge the best of each of them and based on the excellent work SMc Audio did on my preamplifier, I am trusting them to finally solve this dilemma for me, or at least get me close enough that I can quit looking at amplifiers.

@noble100
I find this review of the Kalugas by Audiodrom to be interesting in that they seem to hear some of the same stuff that I heard from the Atsahs but they have different take-always than in the Mono & Stereo review and believe the Kalugas to be reference caliber.
http://www.audiodrom.net/en/power-amplifiers/detail/33-power-amplifiers/556-mola-mola-kaluga
A couple of quotes from the review,

Spatial presentation of the Kaluga monos is enhanced by excellent separation and focus, and brought down a little by slightly subdued ambience – it is as if some part of the spatiality was encoded in the harmonics that are suppressed by NuCore architecture. I could hear the soft ambient echoes of a cello playing in a church, for example, but the trailing off was unnecessarily fast to my ears. However, the width and depth of the macroimage was excellent and images were locked with surgical precision and authority.

The subdued ambience thing is my main downside to NC1200, even more so than the bass, which I could live with by using subs for the lower frequencies.  Below is an interesting observation they make about the bass, 

The dark side of the Mola Mola Kaluga’s bass? Due to no overhang and smear it sounds different from what we are used to. Thus it actually may sound ‘less developed’ to some ears. The audiophile desire to hear the things ‘as they are recorded’ conflicts with the audiophile desire to hear the things ‘as I like them to hear’. Sorry guys, the Mola Mola Kaluga is the former case.

Tim, I said the RM-200 is "really nothing special"? Au contraire! There is much more to the amp than what I wrote above, as a reading of the review by Fremer and Atkinson in Stereophile will illuminate. The "sales pitch" crack was made in reference to past comments by someone (I don't hold grudges, he's entitled to his opinion) about my too often mentioning of the amp. I like to bring to peoples attention over-looked products, like the Eminent Technology LFT-8b loudspeaker, another tremendous bargain.

@fleschler I weigh 182lbs, lol, and my wooden floor, with substantial joists, supports me. My upright piano weighs 500lbs, and there is no problem with it either.

I don’t think stereo components weighing a few hundred pounds are a problem for most structures.