The audio-gd has output levels > 10 volt. So I reduced it to match that of Topping for a proper comparison.
Done that already. I even gave you a link. Here is their measurement again:
Here is mine:
The level is 0.212 dbV or a little over 1.0 volt RMS (couldn't get it to be exact given their volume control and distortion products).
You want to explain to me the difference? Or for that matter why a DAC is tested in "analog to analog" mode of the Audio Precision? That tells me that they did not even try to measure the DAC as a DAC. Because doing so would mean the AP test name would be "D to A." Above I mimicked what they did by testing the pre-amp of the unit. And there, that amp which is the main I/V converter and buffer for the DAC shows lots of distortion. As it should with an amp without feedback.
If we could get -110 dB harmonic distortions out of an amplifier, why would anyone use feedback? We use feedback to get those kinds of numbers. In other words, the measurement they have posted is for a different system, not this.
So go ahead and trust stuff you have not verified. But please don't keep getting personal with me without any data of your own to share.
Where does your 1V figure come from? The peak values between the two graphs don't seem to match, audio-gd's looks to be at -6dB, while yours is at zero, whatever that means.
Why using feedback? To avoid oversized power supplies and the addional cost/design effort implied. Size/weight/cost reduction. Non feedback gears sound more natural to me.
That said, those spikes should make the sound very tubby. And harsh at the same time. These have to be explained. Their level is ridiculously high. I don't know. Maybe the load you are using is not exactly what you think it is, or this dac/amp has defective parts and should be serviced. Or your Audio Precision needs calibration. If it really measures like this, it should sound a bit like crap as far as i know.
Maybe it needs some playing time, as i mentioned, or just some heating up. These gears sound strange for the first 4-6 hours after turning them on. Try to measure it after this delay. Otherwise, contact Kingwa for clues, he should be very helpful, assuming he is not mad at you.
As for me, I am not familiar at all with the AP, can't help you with it. Maybe
@DACLadder could help.
If the gear sounds like crap, the owner should have it repaired under warranty. Never had issues of that sort with my own gears.
I spent my night listening to music using my r2r 7/master-1/nord one up setup. Really had a good time. Measurements are not a religion to me as they are to you. They are not telling the whole story. After all, it is what you percieve with your ears that matters. And that is what makes this hobby worthwhile. I did not buy all that stuff to contemplate graphs all night long, that is not my thing. I need to evade from this crazy world and my audio setup allows that. Even at the office, using the little r2r 11, i get into my world and am able to get perfect focus on what i have to do to move things forward.
The measurement issue should be resolved however, just to ensure that what audio-gd publishes is accurare, and to determine if the dac/amp is in proper condition. This means work for you. I really don't care much about the outcome as long as the measurements are as advertised in the end, either by having your test fixed or by having them modified by audio-gd if they are wrong. I expect the former. I don't mind if it is the latter, it won't change my opinion on the gears. I am a human being, not a device.
The signal levels you were using initially got me upset hence my being personal. You have got to admit you were using ridiculously high levels.