A little deeper on amp power please....

@8th-note If I can add to that:

The power paradigm

I suspect that a lot of what we think of as the need for power is really the need for high current

@erik_squires Current cannot exist without power and vice versa. So if the amp can make the power into the load, it can also make the current.

There are a variety of issues with feedback. One is that the feedback node (where the feedback is applied in the amplifier design) usually is non-linear, meaning the feedback signal gets distorted prior to doing its job. This usually means additional distortion generated on that account, which is mostly higher ordered harmonics (and so IMD as well).

That is part of why feedback has gotten a bad rap in high end audio, but its not feedback's fault so much as shoddy execution.

The second problem is most amplifier designs lack the gain bandwidth product to support the amount of feedback being used as well as the gain of the amp. The result of this is that above a certain frequency, distortion increases. IME this phenomena is highly audible. Most THD measurements are made at too low a frequency to really show what is going on, but distortion vs frequency shows this problem with ease.

Class D offers a way around both problems. I think that is why there are class D amps now that are shutting down class A solid state designs for sheer musicality.

Current cannot exist without power and vice versa. So if the amp can make the power into the load, it can also make the current.

All these years and you still assume I'm typing in the least informed context, @atmasphere , give me a little credit?

I meant to say, being forced to now give an exhaustive/exhausting answer:

Our search for amps that are rated high into 8 Ohms may actually be a search for load invariant amps, that can sustain the voltage even as the impedance drops and the phase angle varies from resistive.   The modern day equivalent of the Krell KSA 50 (50w/channel into 8 Ohms) which was low rated power but able to drive 1 Ohm loads is a rare find indeed.

I think that is why there are class D amps now that are shutting down class A solid state designs for sheer musicality.

Ralph, others have posted here and there with the question "what is meant by musicality?". They do so because the word is vague and not particularly helpful. It connotes something positive and nothing more. When a food critic uses the word "tasty" I cringe and when a person near me claims something he or she is eating is  "tasty" I resist the urge to say "sh*t has taste, but I am pretty sure I don't like it". 

I would love to audition your Class D amps one day but I have heard others and to me they sound very clear, fast, but sterile and without soul. 

And where is the support for the "shutting down" portion of your statement? At the lower end of the cost spectrum certainly. We all know why. And for in-board speaker modules, sure and we again all know why. 

I actually do own and use two digital amps. One is inside a Rotel home theater receiver that replaced a nearly identical Class AB unit that became an expensive door stop due to not offering HDMI connectivity. It sounds markedly inferior to it's Class AB predecessor. The sound is dry and one-dimensional which is no easy feat when there are seven loudspeakers spread around. The other is installed under the roof of an outdoor pavilion covering our patio and powers low-end KEF loudspeakers. It sounds like good crap too. Good for the cost and intended use, but crappy. 

I think that is why there are class D amps now that are shutting down class A solid state designs for sheer musicality

There are some megabuck Class A amps I can't stand to listen to for more than a few minutes at a time, while I've never had a problem listening to ICEpower, so I could see some truth in this.

All these years and you still assume I'm typing in the least informed context, @atmasphere , give me a little credit?

I meant to say, being forced to now give an exhaustive/exhausting answer:

Ralph, others have posted here and there with the question "what is meant by musicality?". They do so because the word is vague and not particularly helpful. It connotes something positive and nothing more. When a food critic uses the word "tasty" I cringe and when a person near me claims something he or she is eating is  "tasty" I resist the urge to say "sh*t has taste, but I am pretty sure I don't like it". 

@erik_squires @fsonicsmith These are both valid criticisms!

Erik, I give you the credit, the reason I responded the way I did is because that sort of shorthand promotes confusion with those that aren't in on the shorthand. I see confusion about this topic all the time so its become a bit of a sore spot.

By 'musicality' I mean its easy to listen to all day, plays bass right, isn't harsh or bright, has good detail without being clinical, has an 'organic' presentation, yet is uncolored. Sorry for the shorthand on my part.

As far as 'shutting down'; most class A and AB solid state designs lack the Gain Bandwidth Product to support the feedback they use; in addition the feedback is misapplied so adds higher ordered harmonics (see the writings of Norman Crowhurst and Peter Baxandall on this issue; neither proposed a solution). The exception might be a zero feedback class A amp which can have ruler flat distortion vs frequency measurements.

Regarding your commend about lower end of the cost spectrum, I think one reason class D has fared so poorly has been insufficient power supplies. IME a power supply for a class D amp has to be robust but a lot of designs I've seen don't seem to reflect that.