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Is MiniDSP SHD's ADC performance in the same ballpark as RME ADI-2 Pro fs?

exaudio

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#1
Given that the MiniDSP SHD and the RME ADI-2 Pro fs both use the same AKM chips, have similar specs, and in Amir's DAC testing showed very similar performance, is it safe to assume that the ADC performance of the MiniDSP SHD is likely to have a SINAD within a few dB of the RME ADI-2 Pro fs?

I ask because I own a MiniDSP SHD and am wondering how close its measurement capabilities are to the RME ADI-2 Pro fs. I tried measuring the THD+N / SINAD with the SHD looped back on itself over balanced XLR. I ran tests in REW, ARTA and RMAA where I tried to mimic @amirm's dasboard settings of 1kHz 0dBFS dithered sine test tone sampled at 44.1kHz/24bit (as stated by @LTig in this post). The results looked very good, but I don't know how valid loopback testing is. I suspect the results are a bit optimistic, but here's what I got:

REW SINAD -122.6 dB(A) THD+N: 0.000074% (A)
RMAA SINAD -122.6 dB(A) THD+N: 0.000074% (A)
ARTA SINAD -118 dB(A) THD+N: 0.00012% (A)


The spectrum plots from each are below.

REW spectrum
1kHz 0dBFS dithered sine test tone sampled at 44.1kHz/24bit
MiniDSP SHD looped back over balanced XLR test tone 1kHz 44.1KHz 24-bit dithered 0dBFS.png

RMAA results:
rightmark_audio_thd_spectrum_test_minidsp_shd.png


ARTA spectrum:
MiniDSP SHD looped back over balanced XLR test tone 1kHz 44.1KHz 24-bit dithered 0dBFS.png
 

Panelhead

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#2
Looking very good. In fact excellent.
It surprising to see this performance. The test signal was generated by the computer soundcard? For REW I run analog into a line input and a monitor out to another line input. Select the second line in as RTA input. This way I can adjust level with signal generator or monitor volume control. Also use the signal generator built into REW. Think the sound card in my seven year old Mac Mini is limiting the results.
The result you are getting beats my Focusrite Clarett 4Pre. I need to try a better computer to see if the test results improve.
 

LTig

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#3
Given that the MiniDSP SHD and the RME ADI-2 Pro fs both use the same AKM chips, have similar specs, and in Amir's DAC testing showed very similar performance, is it safe to assume that the ADC performance of the MiniDSP SHD is likely to have a SINAD within a few dB of the RME ADI-2 Pro fs?

I ask because I own a MiniDSP SHD and am wondering how close its measurement capabilities are to the RME ADI-2 Pro fs. I tried measuring the THD+N / SINAD with the SHD looped back on itself over balanced XLR. I ran tests in REW, ARTA and RMAA where I tried to mimic @amirm's dasboard settings of 1kHz 0dBFS dithered sine test tone sampled at 44.1kHz/24bit (as stated by @LTig in this post). The results looked very good, but I don't know how valid loopback testing is. I suspect the results are a bit optimistic, but here's what I got:

REW SINAD -122.6 dB(A) THD+N: 0.000074% (A)
RMAA SINAD -122.6 dB(A) THD+N: 0.000074% (A)
ARTA SINAD -118 dB(A) THD+N: 0.00012% (A)


View attachment 42548
The REW plot is almost unbelievably good. Actually I don't believe it when I compare your measurements with those done by @amirm. Are you sure that you used an analog loopback and not a digital one?

A loopback testing is perfectly valid as it shows the best performance you can get for test of other equipment. It can't get better than this. The only disadvantage is that you don't know how much noise and distortion is created by the DAC and how much by the ADC.
 
OP
E

exaudio

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Thread Starter #4
The REW plot is almost unbelievably good. Actually I don't believe it when I compare your measurements with those done by @amirm. Are you sure that you used an analog loopback and not a digital one?
Thanks @LTig you're right; it was too good to be true. My testing seems to have been a digital loopback. D'oh! :facepalm:

I connected the MiniDSP SHD's balanced XLR out to its balanced XLR in, but I had the input selector set to USB so that I could use REW's tone generator. Apparently it doesn't work that way. So now I'm not even sure if I can loop this thing back on itself and still generate a test signal over USB.
 

MC_RME

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#5
Definitely invalid measurement. An AK4490 can not reach 122 dB THD+N, period. The noise alone is 117 dB.

Aaah, I see, you found it. Well, for a digital loopback it looks crazy polluted and dirty...
 
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