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[blue_orange]

Is it necessary to turn on the dither when using digital saturation? Even in 24 bit conversion?
I assuming this d.sat is such a dsp processing that might truncate bits..

Any thoughts?

BO

[bobkatz]

blue_orange wrote on Sun, 18 September 2005 14:09

Is it necessary to turn on the dither when using digital saturation? Even in 24 bit conversion? I assuming this d.sat is such a dsp processing that might truncate bits.. Any thoughts? BO

Dither at what bit level? I would say, in general, that it is true, you have to turn on the dither at the wordlength you are capturing.

There is kind of one unique exception to this, and it is the Cranesong HEDD with its unique architecture. It is a totally additive process so the original wordlength remains intact while the 24-bit calculated distortion gets added to it.  Since the wordlength of the source is intact, you could conceivably truncate a 16 bit source at the output of the HEDD and get it back. The distortion will be more distorted, though  

BK

[danlavry]

blue_orange wrote on Sun, 18 September 2005 19:09

Is it necessary to turn on the dither when using digital saturation? Even in 24 bit conversion? I assuming this d.sat is such a dsp processing that might truncate bits.. Any thoughts? BO

Dither at 24 bits? It will make no difference if it is on or off. The use of dither is for when ever you reduce word length, and given that a 24 bits is all you can have (in digital audio data), if you stay at 24 bits, there is no need for dither. Also, at 24 bits, the signal converter noise floor is so much lower than the 24 bits data, that the dither will be buried under the signal noise.

But say you want to reduce the signal from 24 bits to 16 bits. Now you need dither. The soft saturation effects the high level (loud) music, and these are the times where dither does not help you. But when you have a quite part of the music, the converter act in a "regular way", and you will need dither.

So I suggest to view saturation and dither as separate issues. Saturation is for the "music peaks" and for the top range, and dither is for when the music is not loud.

Regards
Dan Lavry
wwew.lavryengineering.com  

[PookyNMR]

While we're on the topic, Dan, could you explain the difference between the "analog saturation" and the "digital saturation" on the m.ad 824?  

I know that (obviously) one is done in the analog domain, while the other is done digitally.  But in the manual (page 11 and 14) you state that the digital saturation has a tape saturation emulation.  Is the analog saturation then only a peak limiter / compressor?  Could you expand on the differences between the 2?

Thanks.

[danlavry]

PookyNMR wrote on Mon, 19 September 2005 20:37

While we're on the topic, Dan, could you explain the difference between the "analog saturation" and the "digital saturation" on the m.ad 824?   I know that (obviously) one is done in the analog domain, while the other is done digitally.  But in the manual (page 11 and 14) you state that the digital saturation has a tape saturation emulation.  Is the analog saturation then only a peak limiter / compressor?  Could you expand on the differences between the 2? Thanks.

Analog soft saturation takes place BEFORE the signal arrives at the conversion. If you drive the AD too hard, so that the peaks go outside the AD input range, the analog saturation will help you, because it reduces the peaks by some amount, and the harder you drive the more it "cuts in". But if you do not overdrive the converter, the feature does not help you at all.

Digital saturation is done AFTER the conversion thus in the digital domain. It ALWAYS boosts the signal level. The boost is 6dB all the way to the -12dBFs level. At higher levels, the boost gets reduced, and the closer you get to 0dBFS (full scale) the less the boost. The "curve" above -12dBFS is behaving like a saturating analog tape.

Regards
Dan Lavry
www.lavryengineering.com

[PookyNMR]

Thanks for the detailed explanation, Dan.