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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: "truncation" - pls explain posted by JayM on February 8, 2007 at 21:00:19:
For a given number of digits in a data word, bits in this case,
attenuation, which is done by division or multiplication with a value less than 1, shifts the significant digits to the right and thus
out of the word.Example:
Imagine a 4 bit system, and you want to attenuate "1111" with 6dB,
which is *0.5."1111" * 0.5 = "0111.1", reduced to 4 bits only = "0111".
So you lost data, as only 3 of the original 4 '1' bits are left.
--
Now with CD's 16 bit standard there is a way of doing at least some
lossless digital attenuation: DAC chips exist with an effective resolution of 20 bits. That's 4 bits more than the 16 bits of the input channel, so you can tolerate up to 2^4 = 16 => 24dB of digital attenuation before really starting to lose data.So with 4 bits signal and a 6 bit DAC the unattenuated scenario
would be:source "1111" => no att. => DAC input "1111.00"
source "1111" => att. by 6dB => DAC input "0111.10"
Which still doesn't make it practical for the large amounts of attenuation required in music volume control.
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Follow Ups
- Re: "truncation" - pls explain - Werner 23:27:48 02/08/07 (1)
- There is also a question of to what degree the loss of resolution is audible. - PAR 06:53:54 02/10/07 (0)
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