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Measurements of Sonore microRendu Streamer

amirm

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#1
NOTE: this is an updated review of microRendu. Measurements were updated to use bitperfect path and max volume.

Introduction

One of the latest trends in digital audio is to use a "streamer" device. This is something that sits between your music server on the home network, with then direct connection to the DAC. A lot of such devices have been built with Windows and Linux operating system on top of PC computer hardware. Sonore's microRendu is different in that it is built as an embedded, black box implementation.

This thread is about its measurements and not a full review. But briefly, this is a tiny device the size of a set of playing cards:



Both the packaging and aluminum enclosure scream "budget" equipment. So if you are getting this device as audiophile bling to impress your friends, this is not it.

The unit as mentioned, is a "bridge." It sits on the Ethernet network at one end and USB connection to the DAC at the other. It is stated that it has more optimized USB interface and power (?). Net result is assumed to be cleaner output in your DAC and subjectively impressions posted so far back this.

The device does not come with a power supply. To make sure I tested mine in some kind of standardized way, I ordered it with the recommended ifi iPower power supply (see http://ifi-audio.com/portfolio-view/accessory-ipower/).



ifi measured specifications say it is much cleaner than even typical "linear power supply." I plan to test the supply by itself in the future. For now, it is being used by microRendu as an integrated system.

Total cost was $702 US dollars.

My test setup was typical of the past. My HP laptop playing a J-test signal connected either directly through a USB cable to ifi DAC or going to microRendu and then the same ifi DAC. In all cases what you see is what comes out of the analog output of the DAC. In other words, it is the sound waves that your amplifier will send to the speakers to be heard.

The input signal (J-test) for this purpose is just a single somewhat high frequency tone. The ideal system will show one tone and one vertical line as analyzed by my Audio Precision analyzer. The J-test in digital domain has an amplitude of -6 dbFS.

For reference, let's start with ifi DAC directly connected to my USB output of the HP laptop. This is on Windows 10 using standard Foobar 2000 with ASIO driver (i.e. "bit perfect output"):

ifi Alone.png

The ifi iDAC2 has three settings. Above is the "standard" output which has a flat noise floor until it drops at higher frequencies. The "bit perfect" switch setting which I am not showing, has an increasing noise floor. For the rest of the tests, only the "standard" setting is used.

The ifi DAC2 by itself shows excellent response especially given its low cost. Noise floor is flat, smooth and without anything to complain about.

J-Test Response Through microRendu
Now let's perform the same test but this time using microRendu as the bridge to the DAC. Because this is a networked device, you have to use a network capable player. On my everyday HP laptop, the only choice I had at the moment was DLNA. microRendu supports this as one of the protocols so it worked out without any issues. Here is the output:

USB versus microRendu with iFi Power Supply.png


This is not good. Addition of microRendu and ifi Power supply has resulted in many new distortion/noise products. The degradation is as much as 30 db! The noise floor is now very jagged, correlated (has patterns) and increased compared to using the DAC direct. We went from the clean, noise floor of the DAC by itself (in green) to this chewed up noise floor.

From psychoacoustics point of view, anything that has such patterns will be more audible than one that is smooth, even if its level is lower. So the addition of microRendu is a step backward in reduction of audible noise.

Mind you, all of this is at very low levels and very likely not audible. But to the extent someone wants to hang their hat on this device having "less noise," they just lost that argument.

Further in the thread I show the increased noise floor to be mains frequency of 60 Hz in US and its harmonics. This shows that microRendu lacks good power filtering and that iFi power supply has a dirtier output than the USB connection on my laptop!

By the way, microRendu comes with a stub/rigid large USB to regular USB connector (don't know what it is called -- sorry :) ). So I also tested with that:




Testing with my linear lab power supply shows the problem to go away:
microRendu with Lab Supply.png


The differences are within variations of measurements so clearly you don't want to use an iFi iPower supply with microRendu lest you want to be worse off than using the DAC direct through USB.

I happen to also have a linear power supply on loan that was design for the Regen, the SBOOSTER BOTW (https://www.sbooster.com/). I was pleased to see it perform similarly to my lab supply:

upload_2017-5-27_13-11-26.png


It has selectable output but up to 6 volts (ifi is at 9 volts and I set my lab to the same voltage). Here is the measured output:

microRendu with SBOOSTER Supply.png


Note:
Testing audio equipment can be error prone. I don't do this professionally and it is possible I have made mistakes. As such, I invite the manufacturer to represent their views, differing measurements, etc. I will be happy to include their comments and/or correct my data.


Summary
The combination of Sonore microRendu and ifi iPower is not good news. Performance is significantly degraded by injection of AC mains input of 60 Hz and its harmonics. If you are going to use microRendu, then you should opt for a power supply like the SBOOSTER that has measured system performance that demonstrates its performance in this system. Once there, this device is useful from functionality point of view in allowing the DAC to sit remotely on a network. From audio performance point of view, the measurements do not show any improvements.

As always, comments and suggestions are welcome. :)

Edit: Part 2 of this review on the hardware front is here: http://www.audiosciencereview.com/f...ore-microrendu-hardware-tear-down-review.770/
 
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RayDunzl

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#2
1: Could you describe a proper J-Test signal? Does it require a transmit device that can jit on demand or is it all in the data? Answers like the third one on this page confuse me.

2: If the microRendu is digital in/out and boosting the digital signal, at what input level does it clip the DAC?
 

amirm

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#3
1: Could you describe a proper J-Test signal? Does it require a transmit device that can jit on demand or is it all in the data? Answers like the third one on this page confuse me.
In the context of USB and streamer devices, just think of it as a pure tone at a single frequency.

In reality and I hope I am not confusing you :), it is a square wave with its level being adjusted by one bit value that causes the samples to differ and in the case of S/PDIF, would cause jitter on the cable to increase.

2: If the microRendu is digital in/out and boosting the digital signal, at what input level does it clip the DAC?
Theoretically, a DAC must be able to resolve all the way up to 0 dbFS.. FS means Full Scale and 0 db FS means right at the maximum.

In reality the filtering/signal processing in the DAC may sometimes cause an overflow. Such DACs will buzz and create distortion during 0 dbFS peaks. This is one of the reasons that -3 or -6 dbFS J-test signals are used instead of full scale.

Note that these are digital concepts. What analog voltage a DAC outputs is up to it. It can output 1.5 volts or 2.0 volts. That is a separate thing than what is fed to it.
 

Purité Audio

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#4
Really interesting Amir, I have already read of the huge subjective improvements.
Keith
 

RayDunzl

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#6
By the way, microRendu comes with a stub/rigid large USB to regular USB connector (don't know what it is called -- sorry :) )
That's a Type A Female to Type B Male Adapter.

At work we referred to that general type of device as a 'gender blender'

This is one of the reasons that -3 or -6 dbFS J-test signals are used instead of full scale.
Well, our professional mastering friends don't restrict themselves to a minus 6.

Whoa! Two things have happened:

1. The output level is much louder. Eyeballing it, it is about +4 db versus -4 db when going direct to the DAC. The difference is a whopping ~8 db!
So, what happens when a full scale digital signal (which you say gets boosted) hits the microRendu and is passed on to the DAC? Boosted to what?

Create a -.01dB signal (or you can choose a more appropriate level) and see what you get on the spectrum of the DAC output.

Does it clip the DAC or not? If not, where is the boost you saw above?
 

cjf

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#7
Nice job on doing this test Amirm. I would be very interested in seeing how various power supplies change the graph, if at all.

I am using the mRendu right now as well and one thing that is interesting is that I didnt sense any sort of increase in loudness when switching to this device from my previous music server which was a lightweight Voyage Linux box running on ALIX 2D2 hardware.

I also have the iFi Device but have not used it yet. I continue to use my Lab grade Agilent DC power supply.

With all the hype around the benefits of using various LPS units these days and the fact that Sonore is coming out with their own "Hi-End" offering it makes one wonder if the results you have shown are already known by the manufacturer hence the reason for them releasing an "improved" LPS that works with this mRendu.

My impressions so far while using the mRendu is that it doesn't sound any better than what I had before (as described above) and maybe even slightly leaner sounding in general then what I had before. This "gripe" is pushing it though because 99% of the time it sounds no better or worse. In my mind this is a good thing and if nothing else the mRendu has made it possible for me to use a better library management software via ROON.
 

amirm

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#8
Well, our professional mastering friends don't restrict themselves to a minus 6.
Indeed. That is why DACs must be able to reproduce 0 dbFS without distortion. My son's Peachtree DAC would clip this way on some of his music which made him go and buy a different DAC (Oppo) without that problem.
 

cjf

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Oh, and I forgot to ask.....Given the more jagged noise floor with the mRendu in place and also taking into account that this jagged noise floor appears to be roughly 10db lower than that shown with using the iFi DAC alone should anyone be concerned with this less than perfect noise floor?

I have often thought about the effect these type of anomalies would really have when viewing measurements in general. By this I mean, anomalies that sometimes appear well outside the range of what is audible to us humans. Should we even care as long as the range that is audible is clean and anomaly free?

These are not meant to be challenging questions but just an honest interest in the answers :).

Thanks
 

RayDunzl

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#10
Indeed. That is why DACs must be able to reproduce 0 dbFS without distortion. My son's Peachtree DAC would clip this way on some of his music which made him go and buy a different DAC (Oppo) without that problem.
You say the microRendu added 8dB.

How?
 

amirm

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Oh, and I forgot to ask.....Given the more jagged noise floor with the mRendu in place and also taking into account that this jagged noise floor appears to be roughly 10db lower than that shown with using the iFi DAC alone should anyone be concerned with this less than perfect noise floor?
The jagged noise is actually higher in lower frequencies with microRendu:



Answering anyway, no, I don't think either is audible. It is just that the technical statements the make about lower noise floor and such are not valid given this data.
 

amirm

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You say the microRendu added 8dB.

How?
Look at the first two graphs. The main peak in the middle is the J-test tone. With direct USB connection as noted on the graph, the analog output level is -4 db. With microRendu, it is +4 db. So the total differential is 8 db.
 

amirm

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RayDunzl

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Look at the first two graphs. The main peak in the middle is the J-test tone. With direct USB connection as noted on the graph, the analog output level is -4 db. With microRendu, it is +4 db. So the total differential is 8 db.
The iFi outputs an analog signal level that is linearly related to the digital input numerical levels.

If the microRendu causes the iFi DAC to output a higher analog level with the same digital level source, there are two options:

1. The digital signal level has been increased by the microRendu - meaning it isn't transparent passing data - meaning, to me if a full scale source signal is processed it will be digitally clipped.
2. Testing error.

Can you digitally loop your source to the analyzer, and while transmitting the same source digital signal, compare the numerical levels of what would be "direct to iFi" vs "massaged by the microRendu"?

60Hz at almost full scale and then amplified by 8dB:

upload_2016-6-17_16-34-46.png


It makes no sense to me that the microRendu would amplify the signal, so, what is going on? 8dB is quite a difference.
 
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John Kenny

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Are you saying that this device is not bit perfect? Shifting bits would presumably be the only way that a digital output can be increased in amplitude?
Have you tested it for bit-perfectness?
 
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dallasjustice

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#17
Amir,

I don't think there's anything inherently wrong with using a network connection instead of USB. AES67 is an emerging standard in pro audio. Look at the noise floor for the merging NADAC. NADAC measurements look pretty typical for a top tier DAC.
http://nadac.merging.com/nadac#perfect-ergonomics
 

amirm

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Amir,

I don't think there's anything inherently wrong with using a network connection instead of USB. AES67 is an emerging standard in pro audio. Look at the noise floor for the merging NADAC. NADAC measurements look pretty typical for a top tier DAC.
http://nadac.merging.com/nadac#perfect-ergonomics
I didn't say there was anything inherently wrong. I said that all else being equal, a networking system has more noise and interference issues to deal with. In the hands of a competent designer, that can be mitigated. It is just an extra barrier due to the need of a processor and operating system whaling away near audio circuits.
 

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Another thing that would be interesting to see would be if throwing one of these guys inline before the mRendu would decrease any noise seen on the chart. If for no other reason than to determine the source of the extra hash seen.

Self powered Ethernet Opto-Isolator

 
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