Moondrops DSPs defective ? : Quarks DSP

Submitted by Acceptable-Exit-9212 t3_11xvoqu in headphones

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2000.01Hz sine 48kHz playback - Quarks DSP acoustic pitch jumps and is out-of-tune.

Output pitch is garbage no matter which playback device or samplerate is used. Based on various comments this is a systematic design issue and not invidual faulty unit. This is sad as it indicates that nobody tested these devices before manufacturing and shipping to customers. The problem was clearly evident after first tens of seconds listening.

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Comments

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SupOrSalad t1_jd6n6ce wrote

On my review of them, I found that every couple seconds the group delay would have a spike where it would delay more than the rest, and then work it's way back, before having a spike again. As well, in the FR you would see a spike or dip in SPL when this happened as well. This was consistent with time, so if you measured it quickly, it would happen once, but if the sweep was much longer, you'd see repeating patterns of this. It's definitely something weird with the dac in it. As well, yeah the pitch seems to keep shifting

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thatcarolguy t1_jd69rl3 wrote

I can hear mine drifting with a 2k tone but I honestly don't notice it while listening to music.

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Acceptable-Exit-9212 OP t1_jd6y3pv wrote

So I thought also, but then noticed that everything sounds very much off-note. And I don't think I have absolute pitch.

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blargh4 t1_jd51e3i wrote

What is the timescale there? kind of curious what that sounds like... a >10hz pitch difference oughtta be plainly audible but I haven't really heard Quarks DSP owners mention it.

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Acceptable-Exit-9212 OP t1_jd55prg wrote

The timescale is on top in seconds. So the pitch sharply jumps every couple seconds. But also this seems to vary and can be more rapid. This was very audible for me and made the device useless. I also wonder why others haven't figured this problem right away. When you once hear it with some static tone then you cannot unheard it even with more complex music.

There has been talk of weird audible effects, group delay measurements and uneven frequency responses with some methods. These are all reflections of this same underlying problem. Maybe some buggy frequency locked loop generating the DAC reference clock.

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PolemiGD t1_jd68ryt wrote

There are a lot of variables here but it probably is just an error of how fourier transform is used in the application. Still there could be more problems with the dac and/ or method of EQ. There are many ways of making digital EQ filters.

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Acceptable-Exit-9212 OP t1_jd6z9qb wrote

I tried many different audio sources etc. and the problem persists. So, the issue is tied with the DAC. Typically such EQs are implemented with IIRs. My quess is that they are using something like CM6533 . Samplerate matching control loop could cause this. (I don't think there is FT anywhere in this part of chain.)

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Bal_u t1_jd73e7s wrote

Good example of why DSP earphones are a terrible idea.

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Acceptable-Exit-9212 OP t1_jd7slio wrote

I still think they are the best idea ever when even half-properly implemented. Sadly this was not the case here.

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Bal_u t1_jd7w8jc wrote

They might work in a higher price range, but getting a good DAC and amp and good earphones for $15 is not really happening.

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