I have both the Tone1 and the Tone2 Pro, so I pulled out REW and connected my Focusrite Scarlett 2i2 gen2 audio interface to see if I could measure any differences between the two. The 2i2 is far from the level of equipment over at ASR (and by Khadas) to measure performance, but I wanted to see what I could learn with what I have at hand.
First up is a frequency plot of the two DACs with an input sweep from 0 to 48 kHz and sampling rate of 44.1 kHz (sorry for the duplication if you’ve seen this in one of my other posts):
Note that the vertical scale is very tight. But it is interesting that we can see some differences, even if they are very small.
Next, let’s take a look at the step response:
Similar but, obviously, the Tone2 Pro inverts phase. Not something that you’re likely to notice, but I wonder if this is intentional. Can be easily solved using Roon’s DSP if anyone cares.
Next, we’ll look at distortion. I like to compare THD to the noise floor, which is admittedly high in my little 2i2 audio interface. But, as long as distortion stays near or below the noise floor, I consider that pretty good. Unfortunately, that’s not the case for the Tone2 Pro.
I thought this might just be an anomaly, so I checked one of my other measurements (48 kHz instead of 44.1), and I see the same thing.
Thankfully, once we get to 96 kHz and above, things look good.
Edit: The distortion I see for DSD64 is the same for all of the DACs that I have, so what you see below must be an issue with my format conversion for the DSD64 sweep. I may try something different tomorrow:
Based on these results, for folks who like using something like HQPlayer for upsampling, I’d recommend PCM 192 kHz for best results with the Tone2 Pro and DSD128 for the Tone1.
For more details, feel free to download my REW *.mdat files from here.
I’m very curious to know what other Tone1 / Tone2 Pro users are seeing and if Khadas is able to reproduce these results.