@brydon10
The linearity definitions criteria is something that's too arbitrary for me.

The ratings on linearity used to be given as +/- 0.1 db on this website (later relaxed to 0.5 db). So the moment it exceeded that, that was considered that the dac was able to do 15 bits "resolution". The idea being that 0.1 db would mean that a dac was perfectly linear to differentiate it from one that was not.

But why not 0.00000000001 db as being the definition of linearity in bits? That's even more perfect right? If so, suddenly a whole lot of dacs including the AP machine would fail that and you'll end up with graphs of dacs labelled "4 bits of resolution which makes no sense. Hence the need for a well-accepted standard that's not made up when one defining bit resolution or linearity as being bit resolution.

**I've asked to see any kind of scientific literature that has the word "a bit" and 0.1 db (or 0.5db) as part of its definition and still have not seen it. For bits, I have seen 6 db being a 1 bit but not 0.1 db. 6 db is 6000% more than 0.1 db. You see my issue here...**

https://hbfs.wordpress.com/2008/12/09/deriving-the-1-bit-6-db-rule-of-thumb/
There is an accepted definition for "equivalent/effective number of bits" which granted isn't really about linearity. But it is an actual defined thing.

**(The Equivalent number of bits)= (SNR – 1.76)/6.02 **
(This equation would likely give you a higher different value for equivalent number of bits - note the 6 db value which is the converter of decibels to bits).

https://www.analog.com/media/en/training-seminars/tutorials/MT-003.pdf
https://en.wikipedia.org/wiki/Effective_number_of_bits
https://www.analog.com/en/analog-dialogue/raqs/raq-issue-90.html
So my fuss this: without an accepted scientific standard, how much you change an arbitary 0.1 db 0.1 db to say 0.5 db or to 3 db makes the linearity figure come out very differently

If you are looking at graphs and you see "15 bits" written there you are likely going to think - this dac can't even do 16 bits! It's not good. CD is 16 bits! I know I did.

But... the SMSL dac can resolve greater than that - just not at perfect linearity. Look at that SMSL dac which looks like it does -80db at 0.1db (13 bits). Relax that to 3db suddenly you are at a whopping -115 db (19 bits) and not -80 (13bits) when using 0.1 db as the limit. That's a large difference in bit resolution and that's why it's important that if we define linearity or resolution this way that we have an accepted standard especially if we use the term bit resolution on a graph.

**Imo if you can hear a dacs linearity of even +/-3db all the way down at even 14 bits (-84 db) in music, Good luck to your super human ears! Good luck if you can even hear anything at all at that low volume in music listening (-84db similar to somebody shouting at you from 10 miles away). **

(Check out the shoutometer for comparison)

https://www.audiosciencereview.com/forum/index.php?threads/the-shoutometer.2555/
**So I'm not sure what real world help this 0.1 db perfect linearity has to your listening experience.** I would be interested to find out if listening tests can show anybody able to differentiate even 3 db of linearity at even 14 bits let alone 0.1 db.