Ronny wrote on Mon, 25 April 2005 02:55 |
Bob Olhsson wrote on Sun, 24 April 2005 23:16 | I'm afraid the word straight from the horse's mouth is that they noiseshape and truncate due to extreme DSP limitations.
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1. It makes no sense to have a noise shaper unless you have noise to shape. 2. The most common application for adding noise to the digital signal is dither. 3. Alesis is too smart not to dither the CD24 file to redbook.
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Unfortunately, Alesis did not provide enough power in the unit to dither, so all they do is noise shape. It take far fewer DSP cycles to do a primitive noise shaping than it does to dither. The advantage of noise shaping is about 1/2 to 1 bit instead of far more with dither. Thus, the grungy, noise modulated sound.
But as another poster recently pointed out, it's subtle, but I wouldn't want to make a replication master with it.
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4. I think that they are following advice that I believe I've heard you mention and that I agree with and that is to dither, regardless of whether you give the user option of type of dither.
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In this case, Alesis is simply doing almost nothing. As I said, there is nothing mentioned about dither in the manual, but there is something mentioned about noise shaping, which is not the same thing.
Ronny, you can have noise shaping without dither. You can noise shape dither or you can noise shape without dither. Noise shaping without dither produces horrid noise modulation and distortion. The Waves type 2 is primarily noise shaping without dither! One of the Waves plugs lets you (or used to let you) choose noise shaping on or off and/or dither on or off. You can see or hear the effect of each option.
Noise shaping is simply feedback from an output point back to an input point, or from multiple output points back to multiple input points with varying amounts of delay. This produces a high frequency boost in the feedback path and it is commonly known as noise shaping. If you insert dither noise in that path, then it is known as noise shaped dither.
BK