After maybe reading one third of this thread and reading a little over at SBAF, I have some questions out of curiosity:
Thanks Amir, for comparing your measurements with the one from Atomicbob. For that, I have two questions:
1. How do you explain the differences in the jitter test? I'm really an amateur and I don't get any of the details of the test. The only thing I noticed are the different frequencies at which you and AB are measuring. Does this influence the outcome of the test?
Yes, it can very much. Some DACs take shortcuts where their 44.1 Khz clock is better than their 48 kHz. My testing is at 48 kHz for this reason. I wish I still had the unit and could measure it at 44.1 Khz to see if that makes a difference.
For now, there are some other differences. I post dBr A which is a relative measurement allowing me to show the signal peak at 0 dB. He doesn't and as such his main signal is at -3 dB. So in all of his jitter measurements the jitter spikes show up 3 dB lower than what they would in my measurements.
Jitter is directly proportional to the input frequency. So all else being equal, the 12 Khz j-test signal brings out more jitter at 48 Khz sampling than 11.05 at 44.1 Khz.
But here is the key thing: once a device is susceptible to jitter, then the device outputting the signal becomes significant. His analyzer generating the digital signal is different than mine and so is his computer. This has been abundantly clear in the case of Schiit Modi 2 where even the length of the USB cable made a difference in its jitter measurements!!! See:
https://audiosciencereview.com/forum/index.php?threads/do-usb-audio-cables-make-a-difference.1887/
Speaking of Modi 2 they too disputed my measurements with their much better looking one. Turns out they used a USB decrapifier which they did not document when the measurements were posted.
Indeed I have shown measurements of Schiit Bifrost where mere activity on the PC changes its output! See
https://audiosciencereview.com/foru...puter-activity-can-impact-dac-performance.22/
Here is what happens when you just change the media player that plays the identical file. Now you see jitter:
Now you don't!
Of course well designed DACs which is the vast majority of what is out there show no such variations.
Finally, I tested the DAC two ways: using USB from my computer and S/PDIF generated by my analyzer. These represent two different sources completely and yet the problems remain. This rules out a lot of potential errors.
2. AB always says something about "is a 16bit DAC and therefore stellar performance if fed with 24bit". For me, this sounds like "OK, might be true, I have to trust your competencies as I'm an amateur and doesn't know better" and this is not enough for me. Can you explain me the test and what AB is referring to? (In laymans terms of course
)
In a nutshell, he is grading on a curve. He is saying because this girl is good looking, let's give her an A even though she got a C in tests.
The DAC chip used in this device is a 16-bit DAC chip because ladder DACs are hard to build at higher precision. For 20-30 years even the cheapest DACs around are 24 bits. He is saying let's forget about everything else and score this DAC as the only specimen, i.e. a 16 bit DAC. There, he ignores his own linearity measurements that show accuracy starting to drop off at just 11 bits, and glitches are visible even with 16 bit signals, and gives it an excellent score. This makes no sense. The alternative to this DAC are others that are 24 bits. We need to compare them apple to apple, not cater to limitation of the design and create all new scoring for it.
The fact that this multi-hundred dollar DAC uses a limited resolution DAC chip is the manufacturer's problem, not ours to make excuses for. Bottom line is that it cannot reproduce 16 bit signals faithfully let alone 24 bit anything. If a manufacturer makes a car that has an anemic engine we don't say it is excellent because all they could muster is a 1 liter engine. If their 0 to 60 times are slower than another car at the same price, it is not our problem that they did not have a more powerful engine to put in there.
So hopefully this is clear. I should add that I now have another Schiit Multibit DAC, the Modi 2 Multibit. So we will be taking another bite out of this Apple.
Stay tuned...