I received my D90SE and measured it today too. But the results are pretty confusing. I’m pretty sure these effects are not, at least completely, due to the DAC chip used, but instead some problems in the implementation.
In any case, I get most consistent results when running the DAC in DSD256 mode using ASDM5ECv2 modulator.
At least some of the problems seem to be due to limited bandwidth of the active components in analog stages causing certain issues. For example the I/V converter must be very high speed amplifier, because otherwise it causes such issues.
First, the DAC seems to be having strange problems with 705.6/768k input rates. First, 1k input at 705.6k is fine:
But the IMD test signal at the same rate is triggering some noise floor modulation issues:
If we then drop output rate to 352.8k PCM, we get best results we can get with PCM inputs. Here’s 1k tone:
And here’s IMD test tone, although here too you can see noise floor jumping up compared to 1k test:
If we then drop 1k tone to -60 dB we see some strange stuff going on with the noise floor:
J-test result is very much fine though:
And for the record, TIM distortion test signal:
And multi-tone:
If we then go down to 44.1k PCM for 1 kHz test tone, result is pretty clean:
From 1k and IMD test tones we can also see the the digital filter has 120 dB attenuation (20-bit reconstruction accuracy). And hint about the analog stage high frequency performance problems, since IMD plot shows 2 kHz tone which is intermodulation of the left-over images:
When we drop level to -60 dB, things get weird again. But this time, the anomalies look like result of active ASRC:
And J-test is not quite as clean, some spikes near the main lobe:
If we then switch to DSD mode and look at 1k at DSD256 using ASDM7ECv2 modulator, we can see that noise floor comes up, but is very clean now and only two harmonics of THD:
Same, but with ASDM5ECv2 modulator, which has much more relaxed noise shaping profile, slightly lower noise floor with modulator noise beginning to appear from 80 kHz up:
Then IMD test with the same, ASDM7ECv2:
And with ASDM5ECv2:
Dropping level to -60 dB now doesn’t produce any suprises either:
And ASDM5ECv2:
Then looking at J-test figure we can see one unknown spurious tone, but otherwise very clean:
TIM test:
And clean multitone result:
I also did THD and IMD tests for DSD512, but again this DAC seems to have problems with higher rates. This is same rate on USB interface as 705.6k PCM, less weird results, but still has some issues:
So I have to say this is one very weird behaving DAC. One possible issue is if the ASRC is enabled, and another issue is if the ESS Distortion Compensation is disabled. For me, this DAC was wasted 900€, I would have expected better performance. It needs fixing on both digital and analog sides…