Originally Posted by Jason Stoddard
“But how can those old DACs possibly perform better than the best of today? They’re only 20/48. We have 32/768.”
Going from 16/44 to 20/44 actually makes more difference than anything else, when it comes to digital. Why? Although the Nyquist theorem says you can perfectly reconstruct a waveform from digital with 2X the sample rate, it assumes an infinite-bit ADC with no quantization error. The more levels, the less the quantization error. 16 bit = 65536 levels, 20 bit = 1048576 levels. 24 bits is 16 million+ levels, but nobody has ever achieved 24 bit linearity, period. The best DACs are about 19.5-20 bits, even after 20 years of “progress.” (Hence, “the lost decades.”) Higher sample rates are nice for analog filtering, but limit the amount of horsepower a digital filter can bring to bear…and it takes up more storage space. So that’s a tradeoff. And “32 bit?” LOLOLROFLCOPTER. There will never be any 32 bit music. Because physics.
Agreed, but this is a case where bits ain't always bits.
There are the sort of bits you're talking about above, which translate into useful dynamic range. Once you start getting to ~20 bits, you're into the heat noise of the equipment. (Hey, helium-cooled DACs!) 32 bits in that sense and not even electrons could move, which would make electronic equipment pretty impractical.
However, there are also the sort of bits that describe how many places your math calculations can run to. So you can have a 64-bit computer OS without setting up your own home liquid helium pumping system, because those 64 bits just describe how much room there is to do math and store stuff. And in fact these sorts of bits are put to use in recording and playback. Some recording workstations allow use of up to 80 bit math when doing DSP. *This* is the (only) sense in which there are 32 bit DACs.
Unfortunately, lack of scruples or just plain ignorance in audio marketing (imagine that!) has confused these two very different senses of the word "bits" in order to try to claim sonic advantages for DACs that use 32 bit processing, which is most of them. 32 bit processing is pretty prosaic stuff, as it's probably half the bits your laptop works with in normal daily life.