The DAC board wasn't explicitly designed for NOS mode, and although everything looked good so far, this is where the tweaking stops.
Hahaha, not quite ...
Three rather important things "happened" :
1.
Yesterday I thought "well, if the thing wants I2S only at high sample rate mode (which is what it comes down to), I'll give it that".
And thus, from within XXHighEnd I could use the Quattro mode (for 44.1 files).
2.
While initially the above had been in my mind the whole day yesterday, and I was wondering whether upsampling from the software would workout better than the upsampling by the SRC chip, at attemping this means of playback it sprung to my mind that I ever developed "just Quattro" mode, meaning a higher sample rate only, and no upsampling. Hahaha, that would do the trick !
Note : this means that all the squares from the earlier scope picture just would stay like that, and each sample is just fed 4 times without adjustment (this was back then made for better jitter rejection).
3.
Playing for 1 minute with immediate good result (at 176400) a next thing sprung to my mind, not thinking it would work, but hoping for it ...
The means of source
I use for the I2S connection is quite different from usual (no Fireface in between), and I notched down the buffer of that means. Note : for 176400 via the Fireface a sample buffer of 128 had to be used (96 or less would not work), which btw is 128 + 64 in real life (the 64 is always there, and is called a Safety Buffer). Now ... I notched down and down and ended up at 48.
Hahaha, so with I2S I now can use the 48 sample buffer for all resolutions ! This is very important because the size of that buffer changes SQ (for SPDIF it does anyway), so the apples and organges thing is out of my life forever ! Only now lowres files can really be compared to hires files !
How does it sound ? (said the reviewer
)
Well, first of all the bird is fully alive now !! But wow, what a different sound once again !
I must again emphasize on "sweet"; Sweetness is what can be heard all over, but the combination with other phenomena is strange :
Now the crispyness is still there. Ok, hard to explain, but as it appears now the sweetness I heard from I2S at OS mode indeed is a property by itself (as I expected). Thus, while OS mode removes the cryspiness and the lively sound, this is back now, but the sweet touch of everything smelling like Sses is still there. Cymbals did not loose there metal (which added "sweetness" would incur for), and all squariness from the NOS DAC is nicely there.
Before I continue I want to make clear somehow how huuuge the difference is with SPDIF. In fact this is just two complete different DACs now. The both connections cannot be compared. Just not. Additionally I must say that I never read about such an enormeous difference between SPDIF and I2S, although everybody does hear "the" difference. This is just not normal, and I am not sure what to think of this. However, theoretically there is this difference :
In OS mode the jitter specs are a few ps only. I am using that now.
In NOS mode jitter is subject to the amount of jitter the DAC is fed with. Remember, this is why I wanted the I2S connection, because I wanted NOS mode. The jitter from SPDIF can well be 200ps or much more. From I2S I don't know it, but I already have my thoughts, looking at the scope and the way steady picture of the perceived clock data (I will measure everything officially in due time).
So, I
think I can fairly state that the sweetness is coming from less jitter. Or the other way around, the roughness as how I know it, comes from high amounts of jitter.
Keep in mind, I am doing something here which other people didn't do before me, and I mean not in the consistent setup of (actually) NOS, a most high grade PSU and tweaking an I2S connection from a PC. And some fine speakers to hear the difference within a second and blahblahblah.
Now, proceeding with the sound quality it seems that I have to remap my mind/memory/expectations from music through loudspeakers;
I know the sound of NOS so well (what about 30 months in a row listening for differences at developing XXHighEnd) that it (yeah what) has become a reference for me. A kind of absolute reference on how e.g. a synthesizer must sound. The same counts for trumpets and everything with very high transients. Of course because it all sounded natural it was allowed to have that reference. But the reference was wrong ...
Earlier in this topic I think I said (or maybe it was offline somewhere) that the "sharpness" of this DAC (just think squares) made my horn speakers resonate at certain frequencies. Also, those frequencies would create standing waves in the room, and e.g. women voices may become unevenly harsh spread over the frequency spectrum concerned. What I did not tell is that I got rid of that by means of some "softener", and the softener just was the (TVC) preamp again. It rounds all squariness so much that all just is fine again.
But guys, the only thing this DAC does is presenting everything very very good as how it receives it. I showed you the square wave at 22050 Hz, and if you can find one picture on the Net that shows a better one ... be my guest. And that was SPDIF with its jitter ...
Now, what the I2S connection shows is that the additional "roughness" the DAC expresses is just jitter from SPDIF; Currently there is no such thing anymore of horn resonance or standing waves at higher frequencies.
The strange thing (for me) at listening to synthesizers, and of course compared to before, is that there now is again "sweet" detail in between the squary tones. Possibly this is best explained when I refer to the feedback of the cymbal to the stick which became audible with this DAC, which has the sweetness I refer to. This is now everywhere, and even a trumpet is not *as* squareish as I thought before.
And please keep in mind how difficult it all is, because like one can just never know how a synth should sound, one also can't know how square a trumpet is blown, which in the end is the same as one can't know how hard the strings are pulled from a bass so metal sound comes from the strings. So, all these things could trick at least me, and it now appears that beyond "natural sound" another dimension exists : real sound. So let's say that natural sound doesn't sound wrong and mimics instruments in general, but real sound makes an instrument sound as how it was played. Hmm ...
The latter gives quite some opportunities. I mean, having all things sounding natural is what I have been working on for a long time, and once you think it can't be improved, the fun is over. But when we now discover that there's also this other dimension, we can gladly be in search of improvements forever, because we just won't/can't know how instruments were played.
I say it once again, the metal from the basses is the most profound thinkable, and there was really nothing in me that could expect it was in the data. Still it is and it could be unveiled.
Right. So the DAC is ready now ? Hell no.
With the just learned data I think some other things can be tweaked. The I2S connection is not the final one, but I first want to measure whether this is ever going to make a difference.
Whether I faked NOS or not, with the current setup all is going through the SRC. Not the best for theories.
To be continued.
Peter
