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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: RE: Why does my 20 year old NON-NOS ladder DAC sound so good? posted by ahendler on June 2, 2014 at 18:57:31:
Multibit sigma-delta-modulation (SDM) DACs take a higher resolution PCM signal and re-quantize it to a lower resolution PCM signal. This lower quantizer resolution (producing higher quantization noise) of multibit SDM DACs is more than compensated for by noise-shaping processing. Such noise-shaping is essentially the same as for 1-bit SDM, except that the quantizer resolution is now as low as possible. Which therefore requires 1-bit SDM DACs to utilize the strongest degree of noise-shaping to compensate. Strong noise-shaping processing is the key innovation of SDM. My recollection is, that the first SDM DACs were single-bit resolution, and that the multibit versions were later developed in recognition of the performance compromises of single-bit SDM.What both multibit and single-bit SDM DACs share is the spectral relocation of their quantization noise to outside the desired audio band. Full resolution PCM DACs don't typically need to do this. The relocated energy is often termed, out-of-band-noise. Since full resolution PCM DACs natively feature lower quantization noise, they don't require noise-shaping. So, you may be wondering, if the first thing SDM DACs do is to reduce the available resolution of an PCM audio signal, why are they so common today? I think the primary reason is because it's very difficult (meaning, expensive) to make a low distortion, yet full native resolution, PCM quantizer. SDM processing enables the utilization of an inexpensive, low distortion quantizer while delivering the low quantization noise of an expensive, full resolution quantizer.
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Ken Newton
Edits: 06/02/14 06/02/14 06/02/14 06/03/14 06/03/14 06/03/14 06/03/14 06/03/14
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Follow Ups
- RE: Why does my 20 year old NON-NOS ladder DAC sound so good? - knewton 21:23:11 06/02/14 (3)
- RE: Why does my 20 year old NON-NOS ladder DAC sound so good? - morricab 08:36:24 06/03/14 (2)
- RE: Why does my 20 year old NON-NOS ladder DAC sound so good? - Tony Lauck 14:37:24 06/03/14 (1)
- RE: Why does my 20 year old NON-NOS ladder DAC sound so good? - morricab 16:07:56 06/03/14 (0)
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