But, tbng, the only part that is specified by Dolby is the decoding - the rest of the signal path (bass management, time delay, D/A conversion, volume control, analog path, etc.) will be different for each piece - that's what Jed M is pointing at, I believe. Besides, if Dolby's specs are anything like the specs we produce in my business, there are plenty of ways (some better than others, some bordering on unacceptable) to build something based on that spec. It's not an absolute. Look at computer video cards as an example - ATI or NVidia develops a chip and designs a card to use it, and then five (or more) manufacturers build their own cards based on that design to use that chip - all of them meet the specs, but all will exhibit differences in behavior. The differences may be very subtle, but they will exist.