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Review and Measurements and miniDSP 2x4 HD DSP and DAC

amirm

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#1
This is a brief review and measurements of miniDSP 2x4 HD Processor and USB DAC. I purchased this online and seems like the price as of this writing is USD $207 as of this writing. This is a USB DAC with Toslink optical input and analog/digital in, four channel digital signal processor (DSP).

The DSP features can be used to implement everything from active speaker crossovers to full room correction/equalization. While the former functionality is easy enough to implement, the latter is up to you to program. This is a "raw" platform with no intelligence of its own. If you want room equalization, you have to figure out how to program its individual parametric filters or FIR parameters.

The unit comes in a shiny aluminum case that feels decent and has just enough weight to not get dragged too badly by the myriad of connections you would have to hang from it:

MiniDSP 2x4HD DSP Room EQ Picture.jpg

Above, I have the USB cable on the right, then Toslink and a couple of "monster cable" RCA interconnects. As you can see, my fat Toslink cable and USB barely fit next to each other.

There is an IR input which I did not test (no remote came with it). But it is super handy to have to switch between settings (e.g. overall room/target curve for your room EQ). So kudos for thinking about implementing this.

What I don't like one bit is that the hardware does not come with software that is essential and mandatory for its operation. Instead you have to go to their website and navigate to redeem a coupon to download that software/USB drivers (if needed). I am assuming they have done this to keep their brother Asian manufacturers from cloning the hardware and benefiting from software that is harder for them to implement. Be that as it may, they turned their problem into ours.

To wit, when I plugged the unit and installed the drivers, even though Windows would detect it as a sound card, I could not get any output from it. Turns out you have to install the "plug-in" package and then select the input to be USB. By default the input is the analog input! This cost me many hours of frustration when I first got the unit.

And why on earth do they call standard desktop app that controls it, a "plug-in?" That too threw me off thinking it is a plug-in to some other software so I kept search for the desktop software. Their website hides that software anyway unless you go through the coupon redemption process even after you logged in and used that.

All in all, made me quite grumpy to get it working. But once there, this thing is not bad! :) Lots and lots of flexibility with two analog channels in, and four out. The software itself uses Adobe AIR cross platform solution so should run wherever AIR runs. I remember vaguely though that AIR is discontinued and if so, wonder what the future holds for using this device with that app.

In this review I am only focused on the device's performance as a DAC and ADC-DAC combo. I did not attempt to use or measure the performance of its myriad of filters and functionality. I will do so in the future. So let's get into measurements and see how it did. If you are not familiar with my tests, I suggest reading my tutorial on audio measurements here: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/.

Measurements
For this testing, I tested three inputs: USB, Toslink and Analog. Let's start with frequency response test of Toslink using 44.1 kHz sampling:

Minidsp 2x4HD Toslink Frequency Response Measurements.png


Channel matching is not perfect although this is a highly amplified graph. The roll off for high frequencies is quite early at 18.7 kHz. There is also some roll off below 20 Hz but not significant.

Here is the response using analog input:

Minidsp 2x4HD Analog Frequency Response Measurements.png


We get slightly more bandwidth to 20.7 kHz and that is it. I am unclear why there is extra bandwidth here since the same DAC is used in both cases. Maybe they both run at 48 kHz and again, the bandwidth is cut off too early. I have not found a way to change or monitor the internal sampling rate. If someone knows how, please comment.

Let's now look at jitter and noise spectrum:

Minidsp 2x4HD Jitter and Noise Measurements.png


I have overlapped both USB and Toslink on top of each other (red/cyan). Performance is identical in both and a step from high-performance DACs like Topping D50. It fits in the class of $30 USB DACs. Nothing horrific though. Just not as clean with 10 dB higher noise and visible jitter components.

Let's compare DAC linearity (ability to reproduce the output voltage representing the input digital PCM samples). Ideal graph would be a line. I tested this using both Toslink digital input and analog input (note, the test conditions vary some):

Minidsp 2x4HD Analog and Digital Linearity Measurements.png


Numerically using my 0.1 dB deviation criteria, the analog input seems to do better by one bit. But its output goes pretty nuts after that, going off the chart at the extreme of -120 dB. Either way, it is average to below average performance and certainly not competitive with well executed desktop DACs.

-90 dB sine wave shows similar situation:

Minidsp 2x4HD -90 db Sine Wave Linearity Measurements.png


Sine wave is recognizable but there is fair amount of noise.

Digging into the spectrum of a 1 kHz tone (itself filtered) with respect to noise and distortion using Toslink input we get:

Minidsp 2x4HD 1 kHz residual noise and distortion Measurements.png


We see quite a bit more noise and distortion than our class leading dedicated DACs. Running the same test where my analyzer generates the analog output to drive the analog input of the miniDSP 2x4 HD we get:

Minidsp 2x4HD Analog 1 kHz residual noise and distortion Measurements.png


Not surprisingly, the analog input underperforms digital, causing higher noise floor and more harmonic distortion. This confirms yet again that you want to use the USB input, not analog.

Let's look at intermodulation distortion using Toslink input:

Minidsp 2x4HD Intermodulation distortion Measurements.png


As expected, the miniDSP significantly underperforms our reference DACs such as the Topping D50.

Similar story exists for THD+N versus level:

Conclusions
As a core audio platform, the miniDSP 2x4HD has OK performance. It has no glaring faults but also doesn't match the best-in-class products either. Seeing how this functionality is part of the larger DSP platform and that component can add noise of its own, this is to be expected. Personally I wish there was a plus version that had better execution on DAC side.

As it is, you would be compromising some performance to gain the benefits of its equalization. That technology if well implement, can make significant improvements to sound reproduction in your room so in balance you will come out way ahead.
 
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#3
Fantastic review as always. Makes you wonder what cleaner measurements would add to Dirac Live.
 

amirm

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#5
Thank you for exploring the 44.1KHz responses. (they are 16 bit?)
My pleasure. The device has a choice of 16 or 24 bit operation. I used the latter. Most of the tests are 24 bits.
 
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#6
What I don't like one bit is that the hardware does not come with software that is essential and mandatory for its operation. Instead you have to go to their website and navigate to redeem a coupon to download that software/USB drivers (if needed). I am assuming they have done this to keep their brother Asian manufacturers from cloning the hardware and benefiting from software that is harder for them to implement. Be that as it may, they turned their problem into ours.
What is so hard about D/Ling software? I have read your complaint before regarding drivers? Seem pretty commonplace these days, manuals are things of the past also. Remember when you purchased stuff and the manual was the size of a small phone book! Which nobody read anyway. lol

I would put cost as a factor, and the fact that by the time something ships, there are often software updates, sometimes several. If someone is underhanded and wants to clone something I would hope they can afford to buy one unit. At least you did not blame Mexico and build a wall around your house. Make audio great again! :D
 

RayDunzl

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#7
I have not found a way to change or monitor the internal sampling rate. If someone knows how, please comment.
Monitor:

Seek out miniDSP Ltd start folder, or go straight to the MiniDSP UAC2 Control Panel via the start/search area where Win10 hides stuff from you.

upload_2018-4-18_19-49-11.png


Setting: not so sure, but REW can do it. That's how it got to 88.2 kHz.

upload_2018-4-18_19-53-49.png


I suspect that is only for the USB input/output, as changing it with analog or toslink as the active input on the hardware doesn't cause any little tick or pop in the analog output.

In fact, looking again, it says "USB Audio Device" on the control panel itself, so, duh.

Toslink would sync to the input, analog has no bit rate, and, according to the meager documenatation, internal operations are always 96khz.
 
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#8
As it is, you would be compromising some performance to gain the benefits of its equalization. That technology if well implement, can make significant improvements to sound reproduction in your room so in balance you will come out way ahead.
Seems like it is a pretty big sacrifice for dsp, room correction/etc. Granted DSP can make a substantial difference in one's system, but is the sound trade off with such an entry level unit worth it? Especially when one makes a serious effort to get the lowest distortion DAC they can afford?
 

oivavoi

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#9
Seems like it is a pretty big sacrifice for dsp, room correction/etc. Granted DSP can make a substantial difference in one's system, but is the sound trade off with such an entry level unit worth it? Especially when one makes a serious effort to get the lowest distortion DAC they can afford?
Whether any noise or jitter or harmonics which are 100 db down are at all audible, is highly debatable. There is no reason not to make devices which measure even better these days, as Topping has shown it can be done cheaply. But can anything here be heard? Perhaps. But I remain somewhat doubtful. The only thing I would be really wary of is using the Mindsp to turn down the volume too much, which will increase the noise and the distortion relative to the signal, as far as I can understand.
 

amirm

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#10
What is so hard about D/Ling software? I have read your complaint before regarding drivers? Seem pretty commonplace these days, manuals are things of the past also. Remember when you purchased stuff and the manual was the size of a small phone book! Which nobody read anyway. lol
Why don't you buy a miniDSP first and then tell me. You can NOT download their software from their website. Here is what you get under "downloads:"

upload_2018-4-18_17-55-9.png


See? No software. You need to redeem a stupid code. And then you are greeted with a bigtime warning that you better know what you want as you can't download anything else if you select the wrong thing, etc., etc.

I test dozens of products on my computer. No way I want to download and install software and drivers if the alternative is for it to plug-and-play with some other hardware.

My job as a reviewer is to comment on things that I don't like. That is what a review is.
 

stunta

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#11
Thank you amir for the review. One of the things I like about the miniDSP is that with REW, you can take measurements, apply them and validate the filters. REW does not provide this functionality which IMO is a missed opportunity. Speaking of missed opportunities, if miniDSP made a new device with XLR outputs and a better measuring DAC, it would be a no-brainer for me.

There is no reason not to make devices which measure even better these days, as Topping has shown it can be done cheaply. But can anything here be heard? Perhaps. But I remain somewhat doubtful. The only thing I would be really wary of is using the Mindsp to turn down the volume too much, which will increase the noise and the distortion relative to the signal, as far as I can understand.
Very good points!
 

Sal1950

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#12
What is so hard about D/Ling software? I have read your complaint before regarding drivers? Seem pretty commonplace these days, manuals are things of the past also. Remember when you purchased stuff and the manual was the size of a small phone book!
Actually, d/l-ing drivers is such a Windoz 98 thing, most gear today is plug&play using kernel based communications. Only thing that's changed with manuals is you have to d/l them too. Now the d/l version is three times the size and written by an Asian with English as his 5th language. :(
 

restorer-john

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#13
Is the software you need the code to download, tied to the hardware somehow- like a hardware/software dongle?

What happens if you want to sell the thing to someone else- can they get the software? And if they can, what's to stop it being copied/decompiled/reverse engineered anyway?

Seems like an unnecessary hoop to jump through.
 

RayDunzl

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#14
What happens if you want to sell the thing to someone else- can they get the software?
Yes, it's $10, but they've started giving it away with a new purchase via a "coupon" - not sure of the conditions there.
 
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#16
You just save the plugin and can sell it with the unit...
You also have unlimited access to downloading the plugins you purchased on the minidsp site
 

svart-hvitt

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#17
Whether any noise or jitter or harmonics which are 100 db down are at all audible, is highly debatable. There is no reason not to make devices which measure even better these days, as Topping has shown it can be done cheaply. But can anything here be heard? Perhaps. But I remain somewhat doubtful. The only thing I would be really wary of is using the Mindsp to turn down the volume too much, which will increase the noise and the distortion relative to the signal, as far as I can understand.
Remember, if you turn down the volume, can you still hear the noise?

;)
 

oivavoi

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#18
Remember, if you turn down the volume, can you still hear the noise?

;)
Serious question or irony? Yeah, the noise of the device is largely independent of the volume. For a good snr ratio, the best practice is high gain in the source and in boxes like this, and low gain in the final amp/device.

That graph for smtpe intermodulation vs level also gives me some concern, but it looks ok when level is not turned down too much. 5 or 10 db down from max seem ok, if I interpret the graph correctly.
 

svart-hvitt

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#19
Serious question or irony? Yeah, the noise of the device is largely independent of the volume. For a good snr ratio, the best practice is high gain in the source and in boxes like this, and low gain in the final amp/device.

That graph for smtpe intermodulation vs level also gives me some concern, but it looks ok when level is not turned down too much. 5 or 10 db down from max seem ok, if I interpret the graph correctly.
My point was serious; can you still hear noise if you turn down the volume?
 
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