Apologies if there is already a thread on this topic, but because of understandable limitations with the forum Search I failed to find it.

You can't avoid it...portable and programable and realistic but is it audiophile ......for me my ears are tuned at Acoustic instruments, natural musicality  and D' class cannot cut it ...

Graham, Proprius analogue transistor allows portability and small enprint.. 

i recall T, Z class in late 1990's to 2005 with overwhelming bass but that is all.  

Whatever the pulse rate, it always produces noise. Take charge-pulse DC to DC converters as an example. For audio, it has to be above our hearing, so if generating a 9V rail from a 5V rail (as in the Voyager), a low rate can be heard as a high pitched whistle, so we take it beyond the audible range.

However, once it becomes a fundamental part of the audio signal, which will be 'inconveniently' subjected to transients, you have a variable and choppy interference generator. Left without output filtering, it will transmit via the speakers and cables as interference. To remove as much as possible, magnetics (ferrite cored inductors) are used to filter the HF noise. They can only go so far, and there will always be a residue. However, the interference remains inside the amplifier circuit (and power supply) and must result in some signal deterioration.

Like aliasing distortion, sum and difference frequencies are inevitable, and although the residue might be in fractions of a volt, domestic listening levels aren't much higher. Beat frequencies occur inside the audible range, which is no part of the original signal and will coincide with elements of the music, leading to fatigue.

Class T reduces fatigue by sweeping the pulse rate up and down within the limits of the magnetic filters to avoid repetitive beat frequencies and reduce listening fatigue.

Nevertheless, there are always beat frequencies (heterodyning), which can never be classed as high fidelity. Class D serves a purpose for arena and stadium sound, where the emphasis is on loud energy, but it isn't high fidelity. For quality public entertainment, a suitably biased class B amp will always produce a better atmosphere and lead to greater audience satisfaction.

Obviously, with no quiescent current flowing in the output stage, class D will consume less energy than class B. However, the pulse generator and comparators consume current of their own unless they can be shut down in 'standby'. If conventionally powered, there will be little comparative energy saving. A switched-mode power supply is required to save idling energy, but there will be little difference in wasted energy between class D and class B when so powered.

With care, class B can be designed not to go into thermal runaway, and in a 100% up-time (always on) design, that's imperative. The 70's amp now idles, consuming about 12 watts per channel with minimal quiescent voltage drift.

If '' Technical expertise allow

For my lay man head ...I dream of a 8 to 12 Watts of Pure Analogue  Class A for High Mid frequencies perhaps with a Valvee flavour  and a Class D digital for Bass and sub bass .

Could also need an electronic Cross over ....to integrate the frequencies and environmental acoustics dispersion 

My part of the job was designing and making the RS232 multiple relay interface to operate the "ghetto blaster" driven by a simple MS Basic sequencing program. Additionally, they wanted a random lamp driver with a stop button to achieve a similar effect as the "Catchphrase" TV quiz screen - it being used to emphasize the marketing bullet points about class D.

I'd attended meetings with the engineers and marketing people in the Oldham factory. All the manufacturing labs had been mothballed, so I assumed the engineers were the designers - after all, the random lamp exhibit boasted far-east production. I'd expected them to send the class D amps as some form of ready to use module to the theatrical model makers, who were to combine it and my control electronics into the "ghetto blaster".

A small board assembly was delivered to my address - no covering letter or datasheet - just the board assembly, to my surprise and horror. It turned out to be the prototype sent from the far east, and Ferranti expected me to produce the amplifier module, probably by ESP!

Darryl and I took turns phoning the Ferranti "engineers" to obtain sufficient data to power the thing up, give it an input, and figure out how to connect the speakers. I think the word I'm searching for is 'clueless' in describing what followed. "Oh yes, the chief engineer will be able to tell you, but he's on leave." Eventually, one of the engineering bods phoned and talked me through the pinout and suggested I try X volts and Y amps and "hope for the best."

It was an educated best guess, and it did work, producing an impressive sound from such a small far-east PCB assembly - that is with a linear power supply several times its size - made in England by me!

Class D is here to stay but true acoustic reproduction can only be achieved with volume of air in a hollow cavity box and bass and sub needs air volume. Mid and high need diaphram needs a very controlled enclosure. 

The technology is far apart..... BUT if an Amp circuit assembly incorporating D and A class with a suitable power supply is KITTED OUT ........there may well be a PRODUCT  for a niche audiophile Market. Graham is testily that it can be done and Britain may need to adopt some of that ''far east '' enterpreneurnial strategy and tactics .....We need to be bold and NEWTON, SHAKEPEAR and  Dysan and Virgin Atlantic .....

That said, I am interested in hearing one though just to hear what 'good' class D sounds like.