busb said:
JonFountain said:
I'm glad to see this topic come up as for the last few days I've been struggling to understand something about Class D and hopefully someone here can set me straight.
In the specification for my Myryad Mi it describes the amplifier secrion as being Class D and further that inputs are sampled at 48 khz to then drive the speakers with a 384 khz PWM signal. Now if I understand that correctly the 'sampling' is not to be confused with analog to digital conversion. However what really still stumps me is whether that 48khz rate nonetheless means that I'm wasting my time using high definition flacs on my Pioneer N50? In fact are Class D amps in general an anethma for high definition music?
Most class D designs are effectively analogue. I'm not sure if anyone has designed a digital version yet that works well. However, 384 divided by 48 equals a whole number of 8. I've read folk complaint that they don't like the idea of their music being chopped up by an HF frequency which makes sense if listening to vinyl but little sense with digital media that's already been sampled!
My Primare class D gives stunning levels of detail & imaging but I'd be frankly amazed if everyone liked the sound - it does not round off rough edges of bad recordings so can sound a little sharp at times. Given good recordings, it sounds amazing. Some prefer a more even rendition of their music collection than my system gives but that's personal choice.
I'd speculate that class D will take over from class AB. Whether class A will be legislated out of existence is no more likely than 3l engines for cars having the same fate. As has been pointed out most phones will be class D with switch-mode PSUs. Primare state that their class D's switch mode supplies conduct little noise back into the mains.
Probably the best known analogue implementation of Class D is B&O ICE power - proprietary to them, but also often used under licence in other brands, such as Pioneer, Rotel, Jeff Rowland, and B&W amongst others.
The so called digital Class D, where the pulse wave for the output stages is generated directly from the PCM or PWM code inputted from the likes of an SPDIF connector is common as the linked Wikepedia article states, in home theatre in a box systems, but much rarer in so called high end product circles.
Exceptions would be the TacT, Lyngdorf and Sony S-Master Pro series, and as the wikepedia article states, these are less appealing from a design POV due to the inability to effectively implement global feedback schemes to lower distortion; instead each part of the audio chain needs to be corrected individiually/locally via DSP; there is also the problem of the amplfiers high output impedance due inablitiy to implement global feedback.
in the case of the Sony S-Master Pro designs, they use a design variant, where the pulse wave is generated from DSD - the amplifier was designed as a statement product, and for M/C SACD; a connected SACD player, via iLink, passes an DSD bitstream from player through the amplifier preamp DSP stages and power output stages, being converted to analogue just before the speaker terminals.
From a sound quality POV, it's the most transparent and ultra high resolution stand alone separates system amp I've ever heard, or had the privilege to own.
It has a massive linear power supply, but nonetheless can deliver a tested 170 watts per channel x 7 channels, all channels driven into 8ohms at < 0.01% distortion, so is no slouch on the measurments side of things, and does it all whilst remaining exceptionally cool running - no mean feat.
To my mind, Class D is the way of the future in terms of getting high performance, low distortion amplfiiers that will give off very little heat and with low power consumption and also fit into small spaces - hence well suited to active speakers, and also as a design considers the environmental concerns in the 21st century re power consumption/green impact etc.
JMac