Class "D" amp? I do not have a clue. Do you?

Coxhous,

ref1000 (10K icepower stock module input impedance) may not be an optimal mach in terms of input impedance for your tube pre-amp. That might be a factor in weak/poor bass.

ref100m has 100K input impedance specifically to perform better with tube pre-amps.

I seem to recall that newer Spectrons may have higher input impedance for use with tube pre-amps as well, more like ref1000m than ref1000.

Also damping factor could be a factor as well. Not sure about Spectron DF but BC 100m is >1000, which is very high and might produce lean sounding bass with speakers that do not benefit. Or it is possible that this particular flavor of highly damped bass may not be to everyone's particular liking. Then again, what is?

The OHM Walsh speakers in my system do benefit from high damping. The bass is more dynamic, cleaner and articulate than with the 120 w/ch amp I used prior with lower damping. The change was pronounced when I switched amps and sounded relatively lean at first, but that was a temporary illusion.

The difference in the bass with my Dynaudio monitors was significantly less noticeable yet also clearly present.

Bottom line is things sound more real and natural to me compared to live now with the BC ref1000ms in my system than ever before.

Also I do not feel that performance is lacking in any significant area now compared to the best reference systems I have heard recently.

I am always actively listening to establish new reference standards that I can target though, so we'll see....

Mapman - you're right about low input impedance. My Rowland has extra board (with THAT1200 intrumentation amp) to increase impedance to 40k.

Channel Islands D-200 user here. They sound just as good as my previous amp, run WAY cooler and weigh a lot less. My previous amp was a Pass Labs X250.5

Kij,
I gave up listening to sine waves sometime soon after I survived the '70s.
Zobel limit on long term power is therefore pretty much a non-starter.

One other MINOR issue, I don't think yet mentioned, of 'd' /ICE is that the frequency response changes as a function of speaker impedance. Lower impedance starts rolloff earlier. The ASP1000 module is worst in this respect being what....about 1/2 db down at 20khz w/4 ohm load?
Give up, at least for now, the idea of flat, wide band response out to X-ray.

I have been an audiophile for over 30 years and after owning tube amps from Conrad Johnson, to Michaelson Austin TV10,VTL,Grant Lumley,AtmaSphere OTL and SET from Cary and a host of good solid state amps, I now enjoy the Red Dragon Leviathan mono blocks-which if you haven't a clue about class D then you wouldn't know anything about my amps either.

All I can report is that I find much to admire about them, little to fault, and that they have been on 24/7 for over a year and no problems.

If they have a "sound" it is something of a cross between a good tube amp and a good solid state amp.
They are smooth, detailed,non fatiguing and have as much power as you are ever likely to need.

They sounded great on Merlin TSMMX,high eff. Tanoy Arden(dc)and on Ref 3a Grand Veena.
They emit no hiss, hum, or any snap crackle or pop.

Noises that most of my tube and solid state amps had.

Th