Scotty:
The ClassD Q&A section had some good info concerning the design.
http://www.classd.org/The following I thought was intresting .At the bottom it mentions TI. I have been waiting for this chip to be implemented in a cost effective product. Of what I have been told by those following the chip wars many where not completely impressed with the Tripath implementation and as I noted in other post I would not and shall not buy a Digital amp for over $1K. But thats just me!
===========From ClassD Q&A Section===========
When is it a good idea to have a class-D amplifier with a digital input interface ?
In the case of real digital amplifiers the interface will be digital by default. This question concerns analogue class D amplifier subcircuits or modules with local D/A converters. This option would be considered mainly for cases where disturbances on analogue input signals are expected. Moving the D/A converter away from the DSP section and onto the amplifier indeed excludes any interference on the analogue signals. Care should be taken before deciding for digital input though. Transmitting the high-speed data and clock from the digital circuit to the amplifier section is likely to produce a fair amount of radiation. Coupling of data and other noise into the clock will cause jitter, making the option unsuitable for real high-quality audio.
Reducing the radiation would either require slowing down transitions (further degrading jitter performance) or moving to differential low-voltage signalling. The latter would probably both reduce radiation and maintain good jitter performance but is quite complicated and expensive. A more effective method seems to be to transmit the analogue signal together with its reference (D/A converter local ground) and use a simple op-amp+4 resistor circuit ("diff amp" or "translator") to translate the signal to the amplifier's local reference. It should be said that some analogue class D products (TI and Philips chips to name a few) actually sport differential inputs straight away.
