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After exploring the options for Multiplexing decoding on digital domain I decided to downgrade this perspective for now. Here are some cone and prose of Digital Multiplexing as I can see them

Pros:

• Ability to have better noise performance. This is till debatable as Digital decoders have 80-85dB signal- to-noise ratio while the do stereo extraction from the composite signal. The well done analog multiplex decoders can do 85dB s/n as well…
• Ability to eliminate analog output stage in case the FM broadcast goes straight to recording  (like in my case)
• Precision of implementation and extraction. Stability of filters.  No need for alignment.

Cons:

• Presence of additional DSP engine in signal path right along with its all peripherals: buffers, data acquisition stages, clocks synchronizers etc…

Now about the options.  Unfortunately it is not a lot. I was not able to found a good D-to-D processor that would take composite signal and will split it to stereo. It should be a card that might be added to PC. Still, considering that I would be probably the only person in the word why would express an interest to buy it and considering the perceives of analog FM I doubt that this card will ever be made. Even if it were made than I still would have a problem as to feel this thing will be necessary at least 172kHz composite digitalized signal (Multiplexing has own bandwidth up to 60kHz)

What is more available are a number of solutions that takes analog Multiplexing and spit out stereo AES/EBU stream. One of better examples is Belar DSD-1 FM stereo decoder.

http://www.belar.com/ib/DSD-1%20User%20Guide%20Full.pdf

However this unit outputs 48kHz at 16Bit. If the 48kHz is fine then who the hell needs 16Bit?! The same processing is done in Accuphase T-1000 and spiting 48/ 16 – a major step back. Even if the digital stereo decoders start output truly 20Bit then the biggest problem in them would be: how doo the internal A/D converters. I presume that the internal A/D will be “instrumental level” with no regard to sound. Of course they are juts speculations and I would very much love to see a digital multiple with integral A/D converters that would much the sound quality of Pacific Microsonics but something suggests me that it will not be the case. Was it my common sense?

Anyhow, BELAR  Electronics  Laboratory

http://www.belar.com/

will come in the end of this year with a new D-to-D multiplex decoder that might do 24Bit output. I might try it… For the time being I will close the door on the idea of digital multiplexing and will stay with analog MPX converters feeding with them my “tested” A/D processors…

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