Understanding DSD to LPCM Conversion, OR SACD "Noise Shaping" for Fun & Profit!

In my prior post on Digital Audio, I introduced two, "simple", Digital Audio formats:  LPCM (Linear Pulse Code Modulation) and DSD (Direct Stream Digital).  These are "simple" in the sense that each stream of LPCM or DSD contains the audio for just one speaker channel -- as compared to the more complex, Bitstream formats which combine multiple channels into a single stream.

However, there is one huge, practical difference between them.  DSD Digital Audio can not be "processed"!  If you have DSD content, and want to convert it directly to Analog audio for your speakers, without any other format fiddling in between, you most forego all types of Digital Audio processing.  So, no Crossover (bass steering).  No Down-mixing.  No Surround Sound processing.  No Speaker Distance adjustments.  No Room Correction.  NOTHING, except for Volume control.

If you WANT any such processing, you must first convert the DSD Digital Audio into a different Digital Audio format which CAN be processed.  I.e., into LPCM.

Which of course raises the question, "Is that SAFE?"  Can you DO that without screwing up the quality of the DSD original?  Or must you give up quality to gain access to that processing?

The short answer is, Yes, it is safe, given properly engineered gear.  Let's take a deeper look at what's going on!

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Digital Audio 101 (...01010...)

The world we live in is inherently Analog. All the things we see and hear, for example, are the result of physical events which are fundamentally continuous in nature. Some portions of your Home Theater are also Analog. For example, your speakers are Analog devices, as are the audio power amps that drive them. And the electrical signals carried on the cabling between those amps and speakers are also Analog.

But modern PROCESSING of both audio and video is done Digitally. And the newest forms of storage and transmission of audio and video are also Digital. In this post we will explore the basics of Digital Audio, with particular emphasis on the LPCM and Bitstream audio formats.

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