Sonore microRendu Review, Part 1
In mid 2014 I received a call from Sonore's Jesus R. He wanted to discuss an idea. Jesus and his team had decided they needed to move the needle, in a huge way, with respect to computer audio playback. They had built, sold, and supported custom high end music servers for years, but were ready to innovate beyond this somewhat traditional approach. Jesus told me they wanted to design and build both the hardware and software for a tiny microcomputer the size of a credit card, that had a single purpose, to reproduce the best sound quality possible. Then he semi-jokingly asked me if I knew anyone with really deep pockets who'd like to bankroll the endeavor. At the end of our lengthy conversation I concluded that this was another great idea that would never come to fruition because it was simply cost prohibitive for a boutique manufacturer.
Fast forward to summer 2015, when I received an email from Jesus with the subject, code name = Toaster. The first two sentences said, "For your eyes only. The small board goes on top of the larger board and it's to scale if you want to print it." Attached was the schematic for prototype units numbered 1, 2, and 3 that were already being made as I read the email. I was pleasantly surprised to say the least. Jesus and his team had successfully pulled off the initial hardware design phase of a project I never thought would see the light of day.
Seeing a product brought to life from its infancy was pretty cool, at least for me. Readers putting two and two together are probably asking what happened from mid 2014 to mid 2015 to the end of April 2016. As anyone with knowledge of hardware design, prototyping, software development and testing, and sourcing components can tell you, there are more trials and tribulations involved in bringing a high precision product to market than Joe Sixpack could ever imagine. But, that's an interesting story for another time. Today, April 28, 2016 marks the launch of the highly anticipated custom designed Sonore microRendu, a purpose-built audiophile microcomputer designed to unprecedentedly process USB audio. [PRBREAK][/PRBREAK]
I want to take one step back before diving into the microRendu because it's important to understand who brought this from an idea to a purchasable product. The microRendu came about through a collaboration between Sonore by simple Design, Small Green Computer and JS Electronics. All three entities have been very active in the development of high quality computer audio for many years. Members of the Computer Audiophile Community are likely well aware of Sonore's products (music servers, signature Rendu, high quality customer support, etc...) and perhaps are as familiar with the Small Green Computer products developed by Andrew Gillis, namely Vortexbox. What most people are completely oblivious to is the fact that Jesus from Sonore and Andrew from Small Green Computer have worked tirelessly behind the scenes with software developers to improve high quality Linux based audio playback. The two have worked for years, herding cats and influencing without authority, to get a global cast of characters to update, adapt, and improve their individually or group maintained Linux software packages. Many improvements to UPnP, DLNA, LMS, MPD, and DSD playback have been driven by Jesus and Andrew, without seeking applause from the countless companies and end users worldwide who have benefited form this work. Then there's "Mr. Wizard", John Swenson. If you want to feel uninteresting and undereducated, have dinner with John. I did at Rocky Mountain Audiofest 2015 and walked away thinking he is one of the smartest people I've ever met, certainly the biggest Shakespeare fan I've ever met, and one of the nicest guys I've ever met. John has been building and designing audio components for decades, including his first DAC that was a whole 4 bits. Around 2000 John started digging deep into computer audio, sound cards, USB DACs, and Linux systems. He has designed some great products over the years, most recently the UpTone Audio JS-2 power supply and the USB REGEN. To pay the bills John has worked at a very large semiconductor company for over thirty years, designing power networks inside custom chips that are used in many devices we depend on every day and the internal circuitry of these chips effects the surrounding components. Trust me, it's way more complicated than that layman's description, but just remember John has likely forgotten more that most of us will ever know.
All three came together to produce the Sonore microRendu. To oversimplify things, you could say Andrew developed the software, John developed the hardware, and Jesus managed the entire project and handled QC. The gritty details are much more intertwined than that description, but the general gist of it holds true.
What Is The microRendu?
To say the microRendu is a computer or microcomputer is true but it's also a bit misleading and may lead to miscategorization. People like to categorize and group things in order to better "understand" them. This is human nature, but it may lead to placement of the microRendu in the same category as Macs and PCs or custom music servers. The microRendu is in a category all by itself. Sure it contains a CPU, RAM, USB, Ethernet, etc..., but that's where the similarities end. The microRendu is a combination of software and hardware, designed to work in concert, to keep processing and ground plane noise a low as possible, while receiving audio over Ethernet and outputting audio over USB to deliver the best possible signal to a digital to analog converter. The end goal is to reproduce the best sound quality possible. How it accomplishes this goal is discussed below in great detail.
First, let's look at this from a more general perspective.
Input bread, depress lever, wait, receive toasted bread. Toasters are dead simple and work every time. Thus, the microRendu's code name of Toaster. Not only must the microRendu produce sonically, it was designed to function like a toaster. Connect to network, play music, hear music. At least that was the idea, and based on my extensive testing, the microRendu is the configurable toaster of computer audio.
The microRendu has a single audio input (Ethernet) and a single audio output (USB). Installation entails connecting the unit to your network and to a USB DAC (or D to D converter like the Berkeley Alpha USB) and powering it up (power options discussed later as well). Configuration, calling it that is a stretch, is done via a web browser by selecting one of about five audio output modes. There are other options that may be necessary depending on one's desired use of the unit, but for the most part it works like a toaster.
I'm sure some readers are wondering why they'd ever need the microRendu or wondering how they might use it in different scenarios. I get it, these same questions were popular when USB DACs entered the market. People used to say, "Why use a computer, can't I just use my CD/SACD player?" The answer is, you can stick with the status quo if that feels more comfortable. You don't need the microRendu in the same sense that you need food and water, but I believe many people reading this will very much want a microRendu. Here are five scenarios where the microRendu really shines.
1. Simplification in combination with sound quality. These two don't often go hand in hand, but the microRendu makes this possible. Currently many people are using a NAS for storage of TBs worth of local music and a music server (Mac Mini, PC, CAPS, etc...) connected via USB to their audio systems. Control is frequently handled by an iOS or Android device. Inserting the microRendu into this chain enables one to remove the music server entirely. This simplifies the audio chain and removes the maintenance and cost of an "extra" computer and all its accessories. The new playback path is simply NAS to microRendu to audio system. All controlled by the an iOS or Android device.
2. A few people in the industry frequently talk about removing the computer from the listening room. Whether this is because their computers are noisy or they just don't like having computers in their listening rooms, that's beside the point. They just don't want one, but they still want all the benefits of using a music server. In essence, the microRendu takes care of this issue. Even though it's really another computer, it's more appropriate to think of it like an audiophile appliance. Once installed, it just works without requiring maintenance. One example of this scenario is the person who has a music server with a few TBs of internal storage sitting in his audio rack and connected to his USB DAC. Maybe the server runs JRiver Media Center or Roon, and it's controlled by an iOS or Android device. This music server can now be placed in any other room of the house, as long as it's network connected, and send audio to the microRendu that is dropped right into the system where the music server was located. Same Ethernet input and same USB output, but now the "computer" has been removed form the audio room and I'm willing to bet the sound quality is even better.
3. Many audiophiles have components with AES, S/PDIF, or USB inputs and they wish they had an Ethernet interface for sending audio the network. Based on the cost of replacing one's component(s) to get that Ethernet interface or the fact that they may have to switch to an inferior product just to get a networkable component, I don't think many people are lining up at HiFi shops to get this functionality if they are already down the non-networkable road. This is where the microRendu comes into play. Connect a microRendu to a USB DAC or D to D converter and one instantly has a networkable audio system. No need to replace one's favorite DAC with something of lesser quality or greater price, when all that's needed is a microRendu.
4. High quality multi-room audio. Using multiple microRendus connected to any number of USB audio devices in different locations throughout one's house is a great way to get the highest of resolutions to almost any system. Streaming 24 bit / 192 kHz or DSD256 to the same or different microRendus is a piece of cake. Use Roon or JRemote for music selection and control of each zone and call it a day.
5. Audiophiles want the best sounding playback system they can afford. Based on my functionality tests and listening sessions, the microRendu could be the solution. I've never had better sounding audio in my room with any other device or server or streamer. Period. Much more on that later. Those who want the best must give the microRendu a spin.
The microRendu's hardware was no small task to design. It took John Swenson over a year to get it right. This often meant getting new boards produced with the smallest of tweaks to eke out the final ounces of performance. In fact very close to the data of launch, Jesus decided to throw away all the newly delivered boards because of a single design change. This change could have been made to the existing boards after the fact, but this team is all about perfection. So, out went the "production" boards and a new order was placed.
At a high level, the microRendu consists of a tiny processor module (System On Module) that's directly connected to a carrier board. The processor module contains an i.MX6 chip with a dual core processor and RAM. The processor module is attached to the carrier board via two 80 pin headers. It's this carrier board combined with custom software that separates the men from the boys and turns the microRendu into a true audiophile class component.
The carrier board contains the regulators, oscillators, USB port, and Ethernet port. Let's start with the Ethernet input and work our way to the USB output. The microRendu contains a 10/100/1000 Gbps Ethernet interface. This interface is limited to 470 Mbps due to the internal i.MX6 bus. Audiophile needn't worry about this "limitation" because 470 Mbps is still hundreds of Mbps more than is required for even the highest resolution audio files. The microRendu features signal conditioning, signal isolation, and EMI suppression on this Ethernet input in part by using a radical power network with multiple regulators between the power to the Ethernet PHY and the power to the USB subsystem. These regulators have a very high power supply rejection ration or PSSR. The PSSR is used to describe the amount of noise that can be rejected from a source of power. Readers familiar with commercial motherboards built to hit the lowest price point will understand this is a huge difference because those cheap boards don't contain much isolation between the power to the Ethernet PHY and USB subsystem. This extensive design may be responsible for some of the network immunity or lack of sensitivity I've found with the microRendu. No matter what I do prior to the Ethernet input of the unit, the sound remains the same. Even using CAT7 shielded cables that break the inherent galvanic isolation of Ethernet by using connected shields on both ends.
The carrier board features a very low jitter oscillator that feeds the hub chip, PLL, and clock network that has anything to do with the USB subsystem. The other on-chip oscillator is used to drive the processor and memory. This is where the software customization comes into play. The design team was able to shut off the processor module's internal oscillator circuit and externally clock the chip from the much better oscillators on the carrier board. Just like externally clocking a DAC, Sonore changed the reference clock of the PLLs to point to the external clock that's fed with the low jitter main clock.
The microRendu has extremely low ground noise due in part to its design and linear regulators, but also because everything not used for audio purposes has been eliminated or completely shut off. There are many noisy processor circuits not simply unused, but totally shut off.
The USB output of the microRendu is equally as special as anything else contained on the carrier board. Most, if not all, commercial motherboards contain extremely noisy DC to DC converters and switch mode regulators. Thus, even though an expensive linear power supply may be used on the outside, the power signal is going through a gauntlet of garbage once it hits the motherboard on its way to the USB output that feeds power to the USB DAC. It's like running a linear supply though a terrible switching supply in order to feed one's DAC. This isn't the case with the microRendu. The incoming power goes through a linear regulator on its way out the USB port and on to the USB DAC. This ultra clean path completely avoids switching regulators.
In addition the design of the microRendu's USB architecture generates a completely new USB data signal and is highly optimized for signal integrity and impedance matching. To quote John Swenson, designer of both the microRendu and USB REGEN, "The microRendu does contain a circuit which is essentially an improved REGEN. There is no need to add an external REGEN between it and a DAC."
The microRendu requires between 6 and 9 volts of power. During its approximately twenty-five second boot time it peaks at about 0.4A and during regular playback settles in at about 0.2A. Using the forthcoming Sonore 7V power supply provided for this review by Sonore, the microRendu uses 1.4 watts during playback.
One of the beauties of the microRendu's design is its' separate power supply domains. The individual supply domains receive the appropriate regulation scheme for their functions. The processor domain uses a high quality switching regulator since it requires low voltage at high current.
The PLLs that generate clock signals for many different systems use a single ultra low noise regulator, while the USB subsystem uses three ultra low noise regulators.
One additional note about the hardware design. One of the first items I noticed upon receiving my unit was the SD card. This card is required, as it's loaded with the operating system. I figured that storing the OS on FLASH (eMMC embedded MultiMedia Card) or NVRAM would have been a better option. It's a good thing I didn't attempt to design the microRendu because my figuring was a bit off. According to John Swenson, "The i.MX6 has three memory subsystems, the DDR3, which we need to use for the main memory of the system, a very small simple, low power SD card subsystem, and the generic everything else memory subsystem. The later is what you use for NVRAM, flash chips etc. It is a large complex system designed to run very fast. This uses a lot of power and generates a lot of noise in the chip. "
The SD card controller is slow, low power and generates very little noise, and on top of that has its own power supply pins on the chip which cuts down even more on the noise it generates. So by using the SD card rather than something like NVRAM I can drastically cut down on the noise in the chip. There are also things like SSDs, but they all need some form of high power bus to talk to (SATA, PCIE etc), which would mean I would have to turn on those subsystems.
On the reliability front, I have actually found that using on board FLASH or NVRAM is actually less reliable. I have worked with several embedded boards over the last few years that have had flash chips, that have had problems far more often than ones that run straight off an SD card. I think it has to do with where the controller is. With SD card the flash controller is built into the card, the software doesn't have to know anything about that. The inexpensive flash chips used with these systems do not have a built in controller, they require the OS to deal with the issues specific to flash memory. Linux has some good code for this, but if something happens with the kernel during runtime, it is very easy for the flash to get corrupted. I had one board that if power went out during boot the flash was guaranteed to be corrupted."
The SD card simply clicks into the microRendu and sits there without requiring any user intervention. If the OS is somehow corrupted or there's a problem with the unit, a new SD card can be placed into the slot very easily. I like this option much better than sending the unit back to Sonore to get re-flashed if onboard solid state storage was used.
Part 1 Wrap-up
This is it for part one of the Sonore microRendu review. I hope readers have an understanding of how the product came to be, who designed and brought the product to market, what the product is, how it works, and some of the main hardware design elements. Of course there are some proprietary features that Sonore won't tell me about and some that I can't tell you about, but that's to be expected with a bold new product like the microRendu.
In part two of this review I'll dig deeper into the Sonicorbiter operating system, selectable audio output modes, and compare the microRendu to the Sonicorbiter SE, and discuss the external power supply options. I'll conclude the review with my assessment of how my audio system sounds with the microRendu connected to different D to A and D to D converters. Before heading off to the Super Bowl of audio shows that is Munich High End, I'll leave readers with this listening impression - I've spent hours on end listening to music since I took delivery of the microRendu. I wanted to make sure I wasn't burned by expectation bias, so I compared it to many other sources and methods of audio playback (both blind and sighted). After all this, I can unequivocally say that with the microRendu in place, my audio system has never sounded better than right now.
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