This is a review and detailed measurements of the multifunction Minidsp SHD Power amplifier with Dirac Room EQ and general signal processing. It was kindly sent to me by a member and costs US $1499 including a measurement microphone.
The SHD Power has a muscular look and feel to it:
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I like the large display and size of the big knob. Then again, for a right handed person I like to see the knob on the right, not left! Sensitivity of the rotary encoder is good for volume changes but not for selection of inputs. It is not predictable how much you need to turn it to change inputs. It also has many functions overloaded into its single click making it hard to use. I understand a remote comes with but I did not have it so don't know to what extent it remedies these issues.
The back panel shows unique set of inputs and outputs;
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As you see from the dual XLR outputs, the SHD Power supports four (4) channels of processing and digital output. If you want to use analog out to an external amplifier, you only have RCA outputs. A good suite of digital inputs are provided from USB to streaming via network. I was unhappy to see that streaming is limited to Airplay only as that doesn't support anything above 16 bits and its conversion from 24 bits to 16 is quite awful. Minidsp should get Roon support for it.
In use, only the bottom of the unit got warm and not that much. So make sure you don't put it on anything hot. Amplification is class D of course but not through any Hypex or ICE modules. Instead, I have read that it uses a TI chip amp (TPA3255).
Minidsp SHD Power Measurement: DAC
Let's start with the DAC performance as seen through the RCA outputs. Spec says that it can only reach 1.7 volts and that is true. Severe clipping occurs above that:
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But look at that excellent SINAD score! This is a very competent DAC implementation in a multifunction amplifier with DSP. It holds its own against standalone DACs:
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And among AVRs and AV Processors, it ties for the best there is:
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Sweeping the output level we see the issue above 1.7 volts:
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Fortunately vast majority amplifiers out there should be able to reach their maximum power at 1.7 volts.
I like the high attenuation of the DAC filter:
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Which indicates very noise floor in the DAC (sorry, forgot to run dynamic range test).
The DAC in use must be ESS as we see a hint of increasing IMD distortion in mid levels:
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My multitone test runs at 192 kHz. Documentation says SHD Power runs at 96 kHz internally. That may be the reason this test result is not as good as it could be:
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Linearity is near perfect:
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Jitter shows a lot of random spikes but some of that is due to low noise floor and at any rate, they are utterly inaudible:
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Notice how both inputs are clean.
This last test was a puzzle:
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Something else other than distortion is dominating this wide bandwidth test. So let's look at that spectrum:
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We see a common technique called "noise shaping" where noise in audible band is pushed out into ultrasonics. That is there regardless of the distortion in the device so heavily degrades the previous measurement. Since we don't hear the ultrasonic noise, it is fine although I do like newer approaches that keep this spectrum clean.
Minidsp SHD Power Measurements: Amplifier
We could have guessed the good performance of the DAC subsystem based on our previous
review of Minidsp SHD. Question then is how good the amplifier is. Let's get into that using digital input which is the only option we have:
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This is well above average performance but alas, not what many of us were hoping:
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That expectation aside, performance is pretty good, especially for a chip amp:
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Crosstalk is excellent although the path here is digital so not fair to analog input amplifiers:
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Frequency response had early roll off but easily fixable by turning on the DSP:
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Noise performance is very good though missing my mark for excellence at 5 watts:
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The amp doesn't seem too happy driving 4 ohm load:
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It shut itself down before clipping (sadly with no indicator on the display). Power available though is much more than specification to the tune of 167 watts. Strangely the spec shows the same power for 8 ohm but that is not what I got:
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Notice the cleaner results now, easily beating our "high-end"
Arcam AVR10. We have a nearly 10 dB advantage in noise department.
I could not run my peak and max power test due to the chip amp aggressive protection mechanisms. This is good for reliability but not for this type of testing or hoping for burst peaks.
I set a lower limit to run power curves for different frequencies:
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At or below 1 kHz response is very clean. Above that it gets erratic. Fortunately audibility of distortion gets lower at higher frequencies so consequences are much lower.
Conclusions
To paraphrase a saying, expectation is enemy of good. Such is the case here. The Minidsp SHD delivers the best performance in the DAC department for amplifiers with equalization. Certainly going above and beyond even high-end AV Processors. Alas, such is not matched by its amplifier implementation, wasting much of the performance of the DAC on it.
I should note that the Minidsp Windows App is a delight to use to program the SHD Power to do what you want across four channels. You can easily convert this unit to make an excellent powered stereo 2-way speaker. Or go crazy and build a 4-way one in mono with ease. Automatic EQ is also available courtesy of Dirac but manual ability is excellent as well. Likely the amp here is more powerful and lower distortion and noise than you find in all but the highest rated powered speakers.
My wish for minidsp is simple: offer a second unit with a Purifi amplifier module in it. And add Roon streaming.
For now,
I am still going to recommend the Minidsp SHD Power. It is a good attempt at excellence in a field where such is very hard to find.
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