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MiniDSP 4x10 HD Measurements
MiniDSP 4x10 HD Measurements
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Old 15th May 2016, 12:17 AM   #1
tomchr is offline tomchr  Canada
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Default MiniDSP 4x10 HD Measurements

Every now and then concerns about the noise level of the MiniDSP balanced output are brought up. As I am considering using the MiniDSP 4x10 HD in my system with a balanced setup, I decided to measure one.

I debated for a while about how to best present the results as there is interest in them both here and on OPLUG. Also, I would prefer that the results can be found easily in the future and forum threads tend to be harder to search. Hence, I have posted the full set of measurements in the Resources section of my website.

I've attached the more exciting plots. The rest can be found on my MiniDSP 4x10 HD Measurements Page: MiniDSP 4x10 HD.

The measurements were performed on my Audio Precision APx525.

Conclusion regarding noise: I would use either the balanced output at the 4.0 V gain setting or the unbalanced output at the 2.0 V gain setting for the best gain structure and SNR. Of the two, my preference is to use balanced interconnects as that architecture moves the ground loop(s) out of the signal path through common-mode rejection.

General conclusion/impressions on the MiniDSP 4x10 HD. At the $500 price point you really get a lot for your money with the MiniDSP 4x10 HD. I do see some room for improvement, in particular in the analog I/O sections and in the software, but I think you get good bang for the buck with this box. In the cosmetic department, it presents nicely on the shelf and I do like the learning feature of the remote control receiver. The MiniDSP 4x10 HD does not come with a remote control but will learn the codes of any remote control using the Philips RC-5, NEC, or Sony RC formats. Those who are into pro audio will like that it comes with rack ears.

Tom
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Old 15th May 2016, 12:32 AM   #2
billshurv is offline billshurv  United Kingdom
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MiniDSP 4x10 HD Measurements
Nice set of measurements, and de-angsts me from using the 4v balanced outputs on my 2x8 . Must finish putting it in box...

Did you measure noise above 20kHz? http://www.diyaudio.com/forums/minid...ml#post4707878 Davey shows considerable ultrasonic noise in his measurements.
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Old 15th May 2016, 01:27 AM   #3
tomchr is offline tomchr  Canada
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Davey just suggested that I take a look at the out-of-band noise. I need to measure the CMRR of the differential inputs as well.

I guess some are concerned with some sort of down-conversion of the ultrasonic noise. If that was the case, we'd have had issues with CD players since the late 1980ies when the delta-sigma converters took hold. Down-conversion also requires a significant nonlinearity to act as a mixer and most audio systems are remarkably linear - in particular compared to mixers.
Without better data, my opinion is that the folks who are concerned with the noise of the MiniDSP are running their DSP into a high-gain power amp. 25 V into a power amp with 32 dB gain (40x) is 1 mV RMS of noise. Into a 95 dB efficient full-ranger or tweeter that's certainly audible. That's my current, skeptical, guess of why some report noise issues.

Tom
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Old 15th May 2016, 01:56 AM   #4
Salas is online now Salas  Greece
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MiniDSP 4x10 HD Measurements
Your last chart shows -85dB hiss like IMD relative to -15dB 2V full spectrum bands signal level. Since many music files have -15dB average as I have seen in Foobar, that level of hiss should be audible at times in high sensitivity speakers on relatively high voltage gain system chains. Maybe like a bit of brightness.
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Old 15th May 2016, 02:13 AM   #5
Michael Bean is offline Michael Bean  United States
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Quote:
high sensitivity speakers on relatively high voltage gain system chains
Don't do that...problem fixed!

Mike
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Old 15th May 2016, 02:43 AM   #6
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by Salas View Post
Your last chart shows -85dB hiss like IMD relative to -15dB 2V full spectrum bands signal level. Since many music files have -15dB average as I have seen in Foobar, that level of hiss should be audible at times in high sensitivity speakers on relatively high voltage gain system chains. Maybe like a bit of brightness.
The last chart is a multi-tone IMD plot. The "hiss" is the IMD, not noise. I think you've misinterpreted the plot, hence, reached the wrong conclusion.

Tom
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Old 15th May 2016, 02:47 AM   #7
tomchr is offline tomchr  Canada
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The CMRR is less than stellar. That's to be expected from a discrete solution, though, it looks like the layout could use some tightening up to prevent the degradation above 1 kHz. Still the CMRR of the MiniDSP 4x10 HD is much better than the 0 dB CMRR of a single-ended solution.

There is some out of band noise from the noise shaping. I'm not surprised. I'm just saying it exists. I'm not seeing anything that changes my fundamental conclusion: You get quite a bit for your $500 with the 4x10 HD.

Tom
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Modulus-86: 40W/8Ω @ 0.000061% THD. HP-1: 3W/20Ω, 450mW/300Ω @ 0.000032% THD. DG300B and Other Tube Circuits.
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Old 15th May 2016, 02:48 AM   #8
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by Michael Bean View Post
Don't do that...problem fixed!

Mike
That's why I designed the Modulus-86 with 20 dB gain rather than the 30+ others use.

Tom
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Modulus-86: 40W/8Ω @ 0.000061% THD. HP-1: 3W/20Ω, 450mW/300Ω @ 0.000032% THD. DG300B and Other Tube Circuits.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 15th May 2016, 02:48 AM   #9
Salas is online now Salas  Greece
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MiniDSP 4x10 HD Measurements
Quote:
Originally Posted by tomchr View Post
The last chart is a multi-tone IMD plot. The "hiss" is the IMD, not noise. I think you've misinterpreted the plot, hence, reached the wrong conclusion.

Tom
Since shapes like hiss that is why I thought it may contribute something like extra bit of brightness in busy tracks.
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Old 15th May 2016, 03:02 AM   #10
Salas is online now Salas  Greece
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MiniDSP 4x10 HD Measurements
BTW did you ever measure the 2X4 model? I got one and it does not sound that great to me when in the chain. Although nice to trace paths for a crossover design etc.
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