I missed this drop so just got this unit via Amazon. And I am not happy. The digital filters can be switched, shown on the display as PCM 1 to 4. But nothing changes in audio. I have the tools to measure frequency response as well as impulse response. Both change significantly and easy to measure when doing this with a Teac UD-503 (it also uses the AK4490 and such offers the same filter selection). But nothing changes with the XD-05, it always works with filter 'Short Delay Sharp'.
I fear that this is a bug in the hardware that can not be fixed, an example of typical chinese development and testing skills (read none).
Of course I have sent two messages to service@xduoo.com and one through the official Amazon channel, on 20 Dec and 22. So far no one replied.
TechlandI re-examined the unit today in detail, also to address some of the replies to my post.
@JCruck: Sorry, but you are wrong. The filters are part of the DAC chip, and that chip doesn't even know where its input signal is coming from. It seems you got confused with the sample rate conversion, which indeed is only available on the digital input, not USB.
@ myself: Further examination of the problem now even more points to a serious firmware flaw. The unit behaves differently between USB and digital input SPDIF:
USB: PCM 1 and 3 are Short Delay Sharp, PCM 2 and 4 are Short Delay Slow. Changing from PCM 1 to 2 'Slow' is activated for less than half a second, then the unit activates SD Slow. The same happens when switching from PCM 4 to 1, 'Sharp' gets active for less than half a second.
SPDIF: SD sharp is active all the time, no matter what is selected. Here also other filters can be seen for a very short time after switching through PCM 1 to4.
SRC: I have to add this feature as it reveals another flaw. Playing back 44 kHz with SRC off, it seems the SRC is not off. The signal looks somewhat deformed on a sample-level. Maybe the SRC is then still on and not properly bypassed - I can't say what exactly is happening. It just looks awful on a DSO to see the impulse response with high-frequency distortion on it. This is immediately solved when using the SRC, so upsampling to 192 kHz as standard operational mode for listening to digital sources would be the way to go.
All of the above is 100% reproducable on my unit. As a technician it seems clear to me that such behavior can not be caused by simple manufacturing errors, like contact problems or defective chips. This looks like a firmware bug, and I would not be astonished if all ever produced units have the very same problem.
And now that I wasted all my time with this I stumbled over the proof of my theory, on a russian website which hosts lots of XD-05 measurements. They show the exact same (wrong) impulse responses for the filter types with PCM 1 to 4.
http://reference-audio-analyzer.pro/en/report/dac/xduoo-xd-05-pcm1-spdif.php
http://reference-audio-analyzer.pro/en/report/dac/xduoo-xd-05-pcm2.php
http://reference-audio-analyzer.pro/en/report/dac/xduoo-xd-05-pcm3.php
http://reference-audio-analyzer.pro/en/report/dac/xduoo-xd-05-pcm4.php
Makes me wonder if Massdrop will show any responsibility and force xduoo to provide a firmware bugfix...
TechlandJust curious, when you change from PCM 1 to 2 and it reverts back to 1, do you also see that on the display? Mine stays at / shows on the display whatever has been selected - 1, 2, 3 and 4. It does not revert back to 1 / 3
I fear that this is a bug in the hardware that can not be fixed, an example of typical chinese development and testing skills (read none).
Of course I have sent two messages to service@xduoo.com and one through the official Amazon channel, on 20 Dec and 22. So far no one replied.