Some of you have seen my previous measurements of Sonore MicroRendu (http://www.audiosciencereview.com/f...asurements-of-sonore-microrendu-streamer.577/). If you have not, this is a device that "remotes" your DAC by letting you use Ethernet networking to connect to a USB DAC. Outside of this functionality, many buy this for the presumed improvement in audio fidelity. My measurements did not show such improvement however. And to this date, no one has produced any that show otherwise.
For a part 2 of this project I thought I open the unit and show what is inside. The unit is inside of a small, cheezy aluminum case. Put aside any expectation of high-end fit and finish here. A couple of screws opens the one end and lets the guts slide out. What is inside is a main "I/O" board on which there is a daughter card that holds the main CPU that runs all the software.
Dealing with the CPU part, it is a typical all-in-one SoC (System on a Chip) on a PC Board with very little other parts than memory. This is typical of Single Board Computers (SBCs) or Evaluation Modules (EVMs) that CPU manufacturers design to make it easier for others to use the part.
The board is an off-the-shelf unit (i.e. NOT designed by Sonore) offered for sale by the company, SolidRun. See this document for the full specification: https://www.solid-run.com/wiki/lib/...rosom:docs:sr-data_sheet-imx6-microsom-i2.pdf
In single unit quantities it retails for $66 which is quite expensive for what it offers. It is just CPU and memory with no networking interface. It even lacks actual USB connectors. The much more widely used Raspberry Pi 3 board retails for almost half as much and has all of these features plus Quad Core CPU.
That said, I am puzzled by the speed and capabilities of this CPU. It is "too good!" If you are going to build a computer that is supposed to be more quiet than a PC which is Sonore's objective, then I would go as slow as possible, and as few devices running at high speed. This same board comes in one core for example. Why use dual core? Why clock at 1 Ghz? Odd choices to be sure.
The "value add" by Sonore is the board that this CPU is mounted on which I call the "I/O" card (short for input/output):
It looks complicated but it is not. Starting from top left, we have the power supply input using the typical barrel type jack. That supply immediately goes into LTM4625 which is a switching step-down regulator. This allows the unit to accept variable input at higher voltages which then gets converted to fixed output needed for the board. Being a switching regulator, it has high efficiency (>80%).
Of note, no matter how clean your input power supply is, the switchmode "post regulator" above will make it "dirty" again, assuming everyone agrees that switching regulators are dirtier than Linear Power Supplies. In that sense, I don't see the focus on using different external power supplies here. Indeed in my testing with two different linear power supplies, there was no difference in performance.
That "dirty" output voltage gets laundered up through yet another set of linear regulators before feeding other circuits. You see a number of examples of them with all that I have noted with the word "regulator" on them. Those linear regulators seem pricey, high performance units so kudos for going the extra miles and being true to their objective of having "clean supply."
The main new functionality there is on top right which is the SMSC USB2412, 2-port USB hub. While I have not checked, I am assuming this is the same approach and part used in Regen. The USB2412 though is nothing special. It is a standard USB hub with no aspirations to doing anything better than taking one input USB port and providing two outputs.
One improvement could come from the clock/crystal that feeds it. That is right below the SMSC input (the part in gold color). The markings say 24.01 Mhz. The spec sheet for the SMSC though says the input clock is 24 Mhz. It is unclear to me why a slightly faster part is used.
Alas, I could not find any parts matching the designations on that crystal. Maybe the "0.01" doesn't mean that it is 24.01 Mhz. And with lack of data on the part, it is impossible to know if it is a premium part or some ordinary crystal.
The rest of the parts from SD card to Ethernet Transceiver are the parts that should have been on the CPU board but are not.
BOM Costs
My quick, back of the envelop cost of material for this unit is around $120 for low quantities. Sonore retails the MicroRendu at $640. So there is a bit of profit in there
.
Summary
Sonore MicroRendu uses an off-the-shelf hobby CPU board as its main computing engine. A simple I/O board with a handful of regulators, some I/O hardware and a USB Hub complete the picture. There is nothing in the design that is unusual or in my opinion, necessary to get better performance out of a high performance DAC. It is the job of a high-performance USB DAC to not care what is upstream of it.
If you are using Sonore MicroRendu for its functionality, i.e. putting your DAC far from the music server computer, that it does. A much more reasonable approach though would be to use Raspberry Pi implementations which will be much cheaper (the Pi 3 retails for just $35).
As usual, I welcome comments/questions/corrections from members and manufacturers.
For a part 2 of this project I thought I open the unit and show what is inside. The unit is inside of a small, cheezy aluminum case. Put aside any expectation of high-end fit and finish here. A couple of screws opens the one end and lets the guts slide out. What is inside is a main "I/O" board on which there is a daughter card that holds the main CPU that runs all the software.
Dealing with the CPU part, it is a typical all-in-one SoC (System on a Chip) on a PC Board with very little other parts than memory. This is typical of Single Board Computers (SBCs) or Evaluation Modules (EVMs) that CPU manufacturers design to make it easier for others to use the part.
The board is an off-the-shelf unit (i.e. NOT designed by Sonore) offered for sale by the company, SolidRun. See this document for the full specification: https://www.solid-run.com/wiki/lib/...rosom:docs:sr-data_sheet-imx6-microsom-i2.pdf
In single unit quantities it retails for $66 which is quite expensive for what it offers. It is just CPU and memory with no networking interface. It even lacks actual USB connectors. The much more widely used Raspberry Pi 3 board retails for almost half as much and has all of these features plus Quad Core CPU.
That said, I am puzzled by the speed and capabilities of this CPU. It is "too good!" If you are going to build a computer that is supposed to be more quiet than a PC which is Sonore's objective, then I would go as slow as possible, and as few devices running at high speed. This same board comes in one core for example. Why use dual core? Why clock at 1 Ghz? Odd choices to be sure.
The "value add" by Sonore is the board that this CPU is mounted on which I call the "I/O" card (short for input/output):
It looks complicated but it is not. Starting from top left, we have the power supply input using the typical barrel type jack. That supply immediately goes into LTM4625 which is a switching step-down regulator. This allows the unit to accept variable input at higher voltages which then gets converted to fixed output needed for the board. Being a switching regulator, it has high efficiency (>80%).
Of note, no matter how clean your input power supply is, the switchmode "post regulator" above will make it "dirty" again, assuming everyone agrees that switching regulators are dirtier than Linear Power Supplies. In that sense, I don't see the focus on using different external power supplies here. Indeed in my testing with two different linear power supplies, there was no difference in performance.
That "dirty" output voltage gets laundered up through yet another set of linear regulators before feeding other circuits. You see a number of examples of them with all that I have noted with the word "regulator" on them. Those linear regulators seem pricey, high performance units so kudos for going the extra miles and being true to their objective of having "clean supply."
The main new functionality there is on top right which is the SMSC USB2412, 2-port USB hub. While I have not checked, I am assuming this is the same approach and part used in Regen. The USB2412 though is nothing special. It is a standard USB hub with no aspirations to doing anything better than taking one input USB port and providing two outputs.
One improvement could come from the clock/crystal that feeds it. That is right below the SMSC input (the part in gold color). The markings say 24.01 Mhz. The spec sheet for the SMSC though says the input clock is 24 Mhz. It is unclear to me why a slightly faster part is used.
Alas, I could not find any parts matching the designations on that crystal. Maybe the "0.01" doesn't mean that it is 24.01 Mhz. And with lack of data on the part, it is impossible to know if it is a premium part or some ordinary crystal.
The rest of the parts from SD card to Ethernet Transceiver are the parts that should have been on the CPU board but are not.
BOM Costs
My quick, back of the envelop cost of material for this unit is around $120 for low quantities. Sonore retails the MicroRendu at $640. So there is a bit of profit in there
.Summary
Sonore MicroRendu uses an off-the-shelf hobby CPU board as its main computing engine. A simple I/O board with a handful of regulators, some I/O hardware and a USB Hub complete the picture. There is nothing in the design that is unusual or in my opinion, necessary to get better performance out of a high performance DAC. It is the job of a high-performance USB DAC to not care what is upstream of it.
If you are using Sonore MicroRendu for its functionality, i.e. putting your DAC far from the music server computer, that it does. A much more reasonable approach though would be to use Raspberry Pi implementations which will be much cheaper (the Pi 3 retails for just $35).
As usual, I welcome comments/questions/corrections from members and manufacturers.
