I recorded with the SBM turned on. Definitely made my recording more shiny in the mids and highs than I wanted. I suggest leaving it off like Mark Nelson recommends.
I'm not sure he suggest turning it off. I recorded with it and found it pretty good but haven't done any comps to be able to say one way or the other yet.
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Got a Map?
The D50 shares something called Super Bit Mapping (SBM) with its more expensive sibling. Here's the scoop: when you select 16-bit recording, the D50 records at 20-bit resolution in order to increase the dynamic range. Normally, the extra four bits are discarded.
Sony PCM-D50 Side Panels
The side-mounted analog input and output jacks also work with mini-TOSLINK digital optical cables.
Engaging SBM recodes the data to squeeze 20 bits of information into a 16-bit word. The idea is to use a higher bit rate to reduce quantization noise and then employ noise shaping to move any grunge away from frequencies we can hear. To test this, I recorded two short clips of my guitar at 16/44.1 — one without SBM, one with. To my ears, there is a difference: the SBM track is more detailed and has less grit.
Here's an uncompressed WAV file so you can hear it for yourself. Pay attention as the guitar trails off into silence — it's smooth as silk.
* Acoustic Guitar with SBM (7.3MB WAV)
Super Bit Mapping is a great addition to the D50, but it makes one wonder: why not use it for all 16-bit files? According to Sony, it's best to turn SBM off if you'll be editing the recording in your computer. The manual doesn't explicitly state why, but it stands to reason that reprocessing the processed signal could create unwelcome artifacts as the computer wrestles with the complex math, accumulating rounding errors. SBM is a shaped dithering process, and digital gurus like Bob Katz (who is very good at math) assert it is best to not dither at each stage, but to wait until the file is ready to be mastered. In practical terms, though, I doubt most folks could hear the difference caused by this extra step.
Super Bit Mapping is disabled when you select 24-bit recording.
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