Originally Posted by michilumin
"Datasheets never include the parts you really need to know."
So, I've learned a valuable lesson on this. And - folks, please, I need to implore. This isn't about it "measuring well vs sounding well". I just, okay, well, let me back up a bit.
I do indeed work with the Super Audio Center, making SACDs and, specifically, helping engineer Sonoma. That will beget a boo and a hiss from some, and an "Oh, OK" from others. I understand - we're trying to make it better and trying to get it to do the higher DSD rates. Really. That's my "stake" in the game.
However, if that could be called a "night job", my "day job" is working with Software Defined Radio and high frequency digital signals.
And then, paired with my DSD alter ego, I'm kind of always thinking about how this fits in with audio. So, I do apologize that that's what's flying through my mind most of the time.
So to answer AMRs question: I have a whoooole lot of scientific acquisition ADCs and signal generating DAC setups in the lab, to test into the GHz range. I've got DSD sweeps at least for DSD128 up to 150khz, and the ability to generate tones and heterodynes up to 500khz for up to PCM 768khz. When you get into the realm of sampling and reproducing RF, this kinda stuff is needed. Most of this is my own software "test harness", some of it comes from RF engineering, some of it from audio. I'm currently in a "chipset mess" myself, dealing with two high frequency ADCs that aren't doing what they're supposed to. So yeah, that's where my head's been at.
Please don't kill me. I'm not just talking about measurements.
I had been familiar with the DSD1700s in the Meitner DACs, and watched TI/BB's development into the DSD1791/DSD1793 chipset (same thing, different flavor; SW vs HW control), and later on into the DSD1792/1794 chips, and most recently, the PCM1795. (Which, I will admit, has good 'gozinta' specs, but not so great 'gozouta' specs. And sounds kind of dull.)
Funny thing, out of those setups, the old, dusty DSD1700 in the Meitners always sounded ... a little bit better to me. According to the spec sheet, they shouldn't. In sound, they just did. So trust me, I am no stranger to the disparity between measurements and sound.
But my concern wasn't "is it good, or is it bad" - for most people, that's all they should have to worry about. For me I really wanted to know if "this new Nano thing" really could "exhibit" DSD128 and DSD256, and, it turns out, indeed-it-do.
To determine that, "true or false", not qualitative - a "benchy, measure-ey" test was needed. Again, a "litmus test", Y or N, not a qualitative test. Needless to say that "while I was in there", I noticed that the Nano performed... impressively. Please understand: Performing a heterodyne test near Nyquist frequency is a legitimate way to tell what sample rate a device is operating at, at least "positively". It's not a "measurement", it's a binary check. If there's not a filter in the way, it'll tell you. If you put a 180kHz heterodyne into a system running at 24/192kHz PCM, you'll get either nothing, or a real mess, out. However if you do get the same clear signal you put in, out of it, then, that's proof that it is running at that rate. So I'm not suggesting the "quality" of such a device should be measured, this was more of... exploratory surgery.
And now that I think of it, after all this mess - there's more oddity in the mix: The old DSD1700s can do DSD128.They're not supposed to. The old DSD1700s can almost do whatever you tell them to. Sorta. I mean the specs sure don't say they can - they were made in a time when if you said "DSD128" you'd get a blank stare. Or if you even said "PCM 24/192" you'd maybe get a tilted-head glance. So, really, AMR basing these DACs on the "slight" evolution of those chips, the DSD1793, makes a whole lot of sense now..
Basically, I had my eyes glued to the damned TI/BB spec sheet. And was doing what a lot of engineers tend to do after being mired in projects after a while: not thinking outside of the parameters. What AMR said about needing to know what went on inside the silicon, and even knowing some of the chip developers, all makes a whole lot of sense to me now.
I really feel that my approach here on head-fi was wrong. I meant to be incredulous but not outright denying, and I took that too far. Trust me, I feel bad. I had to take a few days off listening to my Nano because of what transpired here. And i'll probably go back to read-only mode after this.
But it was based on a cynicism that I've gathered up dealing so often lately with "promised functionality" not being "delivered functionality". And I am sorry that that colored this. And I need to put it in check. When I heard "AMR runs the DSD1791/1793 in a secret, unsupported manner", my first reaction was "Oh come on."
But, after testing it, and finding out that, indeed, it does, I gotta say, thanks for doing engineering "the right way" vs the "confined" way. I always preached that, and this week I found myself caught up in it.
Not good. But maybe there's a reason for everything that transpires. Think outside the box, and all that. AMR is certainly doing that.