Here is some more about the subject:

1) http://www.analog.com/static/imported-files/tutorials/MT-003.pdf

2) http://www.analog.com/library/analogdialogue/archives/39-06/Chapter%205%20Testing%20Converters%20F.pdf

Reference 1) is good for understanding concepts on ENOB and SNR stuff. Reference 2) talks a bit about the same and INL and DNL. Flip to page 5.12 on the second reference and one may find a possibly explanation as to why INL and DNL are not commonly provided in some audio DAC datasheets:

"Finally, there are several types of DACs which generally do not have static linearity specifications, or if they do, they do not compare very well with more traditional DACs designed for low frequency applications. The first of these are DACs designed for voiceband and audio applications. This type of DAC, although fully specified in terms of ac parameters such as THD, THD + N, etc., generally lacks dc specifications (other than perhaps gain and offset); and generally should not be used in traditional industrial control or instrumentation applications where INL and DNL are critical. However, these DACs almost always use the sigma-delta architecture (either single-bit or mult-bit with data scrambling) which inherently ensures good DNL performance. DACs specifically designed for communications applications, such as the TxDAC-family, have extensive frequency-domain specifications; but their static specifications make them less attractive than other more traditional DACs for precision low frequency applications. It is common to see INL and DNL specifications of several LSBs for 14- and 16-bit DACs in this family, with monotonicity guaranteed at the 12-bit level. It should by no means be inferred that these are inferior DACs—it is just that the application requires designs which optimize frequency-domain performance rather than static"

BTW: I'm not sure about the Analog Devices "should not be used in traditional industrial control or instrumentation applications". Not saying it isn't true. Just not sure about that. What is a little more clear to me though, is that for delta sigma INL and DNL are not as straight forward measurements as with ladder DACs. I can say also I didn't use those (INL/DNL) for modeling communication system performance either.

Alright, so I did some more digging into audio DACs. Most of them are indeed delta sigma. Most of them cannot do more than 20 bits of resolution. They seem limited by noise.

Again, there seem to be a trade-off between sampling rate and number of bits, regardless or architecture.

If one feels comfy with ladder DACs and those give out 20 bits, I guess life is good. One might need to take care of the sinc frequency response shaping that comes with it though, but that's another story. I do think there are flagship delta-sigma DACs that can give 20 bits of resolution. Perhaps the PCM1795, CS4398, or maybe the ES9018K2M can (last one gets closer to 21 bits). IMO it's just another way to get from point A to point B.

It maybe possible to come up with a DAC (delta sigma or ladder) with higher resolution. But so far I haven't seen > 20 bits of effective resolution, INL/DNL plots or not, and either ladder or not for BWs that will cover the audio range. I definitively could be wrong.

I also do not subscribe to the belief that we have gone back 20 steps back with delta sigma and that proof of that is that one will never put that technology in critical applications. I also don't like the bringing up of military applications and credentials. Proly an irrational pet peeve of mine. I believe that for the sampling rates that those applications require, delta sigma may not be appropriate. But I do not currently feel that has anything to do with "accuracy".

Furthermore, all of this does not take into consideration implementation, which can render those wonderful 20 bits of resolution to crap.

All of what I write here is IMO, and I could be completely wrong, and I'm more than open to be corrected in my mistakes. I also have a lot of respect for Schiit products and expertise.

Just had another thought.


Given the same temperature and other conditions, it would seem that the INL/DNL plots of ladder DACs would be reproducible. In effect, they are always going to make the same error.


With SD DACs, would the INL/DNL plots look slightly different every time the measurement is taken because of the randomness of noise shaping?

TI DAC8581. Industrial DAC chip which could be the one used in a well known NOS DAC.

It's a "16-bit" DAC. Well sort of. Look at the LSB error in the INL plot. I believe that INL error pattern is typical of ladder DACs.

Any recommended reading sources that might help someone understand how to read these measurements? (I'm hoping my computer science background will help me get up to speed more quickly, where I did take one class that dabbled with assembly programming and other stuff specific to the bit level, but a lot of that has been dumped from my brain already.)

I could tell the measurement wasn't good based on your comments, haha, just wasn't sure what I was looking at. OK, so 15 LSBs would be 4 bits off for 16 bit. Stuff like that is what I was asking if you had recommended reading for. Looking around myself as well to get myself educated, just wondered if you stumbled on anything easy to understand or digest. (Admittedly, this bit-level stuff, especially dealing with LSBs or MSBs went mostly over my head in that class, but maybe something is still stuck in my brain.)