Where to go after Bel Canto Ref1000MKII

Mapman, yes they are related since negative feedback lowers output impedance but class D has pretty low output impedance to start with since speaker is always connected to low impedance source (GND or V+) with Mosfets and only direction changes. What benefits our speakers might be not the best with other already over-damped speakers. With class D they often complain about loosing bass. It is also matter of personal taste. I like well defined bass, meaning short when it supposed to be short and long if it is recorded that way, but many people like round, loud bass all the time. One cannot argue with taste. I also noticed improvement in quality of the bass with more natural attack and decay - very pleasant with well recorded acoustic bass. It is possible that my amp and speakers just like each other. Negative feedback improves everything but increases Transient Intermodulation responsible for odd order harmonics and bright sound (overshoot in time domain). Here is example showing how feedback improves DF that I posted a while ago:

Let’s take amplifier that has gain of 30 (31.6dB). When input voltage is 1V output voltage is 30V. Output voltage drops (for whatever reason) 1V under 1A load to 29V. That's 1ohm output impedance (DF=8).

Now, let's build this amp with gain of 300 but feed 3% of the output voltage back to the input in opposite phase. As a result amplifier’s output is the same 30V as before but input is the difference between 1V and 3% of 30V = 0.1V Let’s verify (1V-0.03*30V)*300=30V

Let’s load this amplifier with 1A. Our voltage drop inside is still 1V under 1A load, but output voltage will be higher than 29V because we subtract less from the input. Output voltage will be 29.9V and output impedance will be 0.1V/1A=0.1ohm (DF=80). Let’s verify. (1V-0.03*29.9V)*300-1Vdrop=29.9V.

Output impedance dropped 10 times. Expression 1+B*Aol is known as “Improvement Factor”. In our case B (“Feedback Factor”) = 0.03 (3%), Aol (“Open Loop Gain”) = 300 thus Improvement Factor = 1+0.03*300=10.

KIjanki,

I really appreciate the highly damped/articulate/powerful bass with well recorded electronic instrumentation/recordings in particular, though I would agree with the benefits for acoustic bass as well. I cannot listen to many such recordings any other way in that they seem to totally fall apart into a muddy mess if the bass drivers are not optimally controlled.

Mapman, acoustic bass has very good bass definition, being long scale instrument, in comparison to bass guitar (unless slapped). If feel sorry for the guy who had to carry this instrument if my system cannot do it justice.