Why not more of the same? [Archive] - Audio & Video Forums


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05-16-2006, 05:50 AM
I've recently acquired a couple of Sony Masterworks Expanded Edition discs and they are most acceptable. The blurb on the cover reads:

--"Features Sony's DSD System and SBM Direct for best possible sound quality"--

Without trying to revive the medium v. method thread/argument, what is SBM and is
DSD/SBM cost prohibitive? If not why do we not see this as a regular mastering technique?


05-16-2006, 07:15 AM
DSD is the one-bit digital audio format that's used with the SACD disc format. DSD was originally developed by Sony as an archiving format for their library of analog master tapes, which have a finite shelf life.

SBM stands for Super Bit Mapping, and that's Sony's method for downconverting high res digital audio during the CD mastering process. SBM is on plenty of CD labels, particularly high res remasters of vintage recordings. No idea if it's any better or even any different from other downconversion methods. SBM Direct applies to the process used for downconverting DSD audio.

In this case, Sony likely archived the original analog master tape to DSD first, and then used the SBM Direct downconversion to create the 44.1/16 track on the CD transfer. A technical explanation of SBM Direct from the SACD white paper is clipped below.

Downconverting Direct Stream Digital from 1-bit/64fs to 16-bit/1fs
is not theoretically difficult. Every DAT recorder and A/D converter
has a circuit that does much the same thing. But we needed to
downconvert DSD in such a way as to retain the maximum possible
signal quality in the 16-bit world. The answer was to completely
filter and noise shape the DSD signal in a single stage.

Thus, interstage requantizing errors would be eliminated. Aliasing would
be minimized. And ripple would be suppressed. Sony designed a
super-power one-stage FIR digital filter/noise shaper with an
amazing 32,639 taps. This is Sony’s real-time Super Bit Mapping
Direct processor.

Just as Sony’s existing Super Bit Mapping™ circuit helps
approach 20-to-24-bit precision in 16-bit digital audio, the new
Super Bit Mapping Direct processor enables DSD to be released
on industry-standard Compact Discs with audibly superior
performance. Subjective comparisons conclude that much of the
original DSD benefit is preserved in 16-bit Compact Disc release.

Dusty Chalk
05-17-2006, 12:12 PM
SBM has existed long before DSD, I believe. It pushes the dither noise up into the highest frequencies (coincidentally, so does DSD), in a realm where it won't be heard on most consumer gear. It's not really "DSD on CD", though -- that's overstating things.

It sounded audibly superior when I first heard it, haven't listened to it in a while, though.

05-17-2006, 07:39 PM
Sony has always made it a point to develope their own method of archiving, down converting, file compression for playback (MiniDisc), recording/playback for movies (Beta)...Why? Beats me...I own a few SBM 20bit CDs and I couldn't say I've heard any improvement. Of course, I don't think I could since most common players are still using the 16 bit converters (standard CD).

I have not heard any SACDs though. When they settle on one type of playback format or make a universal player that plays all types of formats (SACD, DTS, DVD-A, HDCD, high bit rates, etc) I might make the plunge, but not until then.