Metrum Acoustics AMBRE: a network player that connects in more than one way
Following a first introductory article on the Metrum Acoustics Amber, today we are to look deeper into this device.
Metrum Acoustics is a manufacturer recognized for its R2R-based DACs. They have however a larger range of products including a power amplifier called FORTE and a DAC Headphone Amp, the AMETHYST
Metrum Acoustics offers a modular hardware approach to its products, leaving open the field of evolution. As an example, we can mention the availability of modules providing the MQA functionality for DACs, but also i2s input modules (on RJ45) instead of USB. As such Metrum Acoustics offers to support its customers for the connectivity of the i2S which is far from standardized. For information, you will find on this link, a document that consolidates the different variants and wiring of the i2S. Metrum Acoustics practices direct sales only and a 30-day loan (product purchase and refund) is possible.
AMBRE, available in black or silver facade, completes the range by offering the reading of dematerialized music files. This product consists of:
a substantial power supply that seems to be the same as the DAC / Amethyst Headphone Amplifier.
a main board managing input / output (AES / SPDIF / TOSLINK / i2S) but also the interface with the heart of the network drive
Raspberry Pi 3 B +. This Raspberry is connected to the main board via its connector. The power supply of the Pi as well as the management of the inputs / outputs of the main board are done only through this connector (no power of the Pi by the micro-USB connector of 5V for example).
There is an ethernet link between the Pi and the main board. This link is all about “optical decoupling” between the pi and the main board. The link being provided by a simple ethernet cable. The ethernet link is galvanically isolated and does not directly use the Pi Ethernet input.
The main board houses the TOSLINK, AES and i2S connectors. The SPDIF connector on RCA is remote, I guess for lack of space on the PCB vs product size. This has at least the advantage of being able to replace the RCA with a BNC for those interested.
The facade carries 3 LED indicators: one for the LAN connection, a second showing the playback of an audio file and the third blue color on which I will return later, representing the product startup status.
There is no particular decoupling at the level of the feet which proves to be fairly standard products in “rubber”.
The “smart” heart of this product is therefore a 3rd generation Raspberry Pi in its latest version (B +). This approach already implemented by many manufacturers (we can mention Allo who just released the signature version of its best-seller: the DigiOne) brings modularity and scalability both in hardware and software. Metrum Acoustics was therefore initially dedicated to making its network drive compatible and Roon certified. They started from a low-consumption distribution base (loaded in RAM) and implemented Roon: RoPieee. You will find below a brief description of this distribution.
For the tech savvy: it’s Archlinux based, runs a custom 4.9.x kernel
with the latest DSD patches, runs completely in RAM, uses the F2FS file
system for preserving the flash card as much as possible, supports
native DSD for a reasonable set of DAC’s and updates itself automatically. For that I’ve (for now at least)
implemented a crude mechanism where the RPi reboots once every 24 hours
and after that checks for updates. So basically, it follows Archlinux
rolling release model, with on top of that Ropieee’s software and the
At present, Metrum Acoustics has certified its device at Roon on the basis of this distribution. In this sense, when RoPiee has finished loading, the blue front LED stops blinking, which is not the case if you want to use other distributions. One point Metrum Acoustics is working on since ‘they are looking to open up more of their product to the community.
You can access the settings of the distribution and the device by pointing to the IP address of the Amber in a browser. Access to SSH for is always possible using the Username / Password common (root / root).
This distribution can reboot at regular intervals in order to validate the presence of updates in “stable” or “beta” version, to be configured via the “advanced” tab.
The base of Amber being a Raspberry Pi with a part “sound card” identified as “Hifiberry Digi + Pro”, it is quite possible to install other distributions. Note that Metrum Acoustics is quite open to users continuing their experience in this direction, by allowing the opening of the Amber to be able to make changes to SD cards.
So I started implementing Dietpi and PCP by customizing my need for Dietpi(GMediaRender, Squeezelite, Shairport, BubbleUPnP Server). This customization makes it possible, among other things, to access Qobuz’s streaming via OpenHome or LMS). I used the configuration tools of dietpi to cut the wifi I do not use, turn off the Bluetooth and reduce the consumption of usb ports(no need).
Everything works perfectly except the blue LED on the front that keeps blinking. While waiting for Metrum Acoustics to take this into account, the masking tape method is certainly the best.
Metrum Acoustics relies on two clocks from Tentlabs. In 44.1 and 48kHz of course handling the multiples of these frequencies.
I picked up some usual playlists:
Birdy – Live in London: Skinny Love
Rodrigo y Gabriela – Live in Japan: Stairway to Heaven & Tamacun
Vianney – The Acoustics: Man Down
Avishai Cohen (Double Bass) – Live Blue Rating: Remembering
Aron Ottignon – Live @ Funkhaus Berlin: Waterfalls
Sophie Hunger – 1983: The wind will bring us
Hadouk Trio – Live @ FIP: Loukoumotive
As far as the tests are concerned, they have confined themselves to trying the AES and SPDIF outputs because of not having a compatible i2S DAC at hand. Regardless, these two outputs should be the most commonly used by customers of this product. In terms of distribution, the returns below are based on RoPiee, thus the base distribution of Metrum Acoustics. I will add my feelings about the other distributions (if there are any) in the days to come.
What strikes as soon as the product is powered is its ability to manage the pace of titles but also different sound plans. However, I was raised very early in the streamers excelling in this field (BelCanto RefStream, dCS Network Bridge), and clearly this Amber has this legacy. It is important to be able to compare this product with a Pi-based equivalence. On the rhythm and scene axes, and it’s still happy considering the price difference,
AMBRE brings much more than a DigiOne Player (with stock supply Allo or linear power supply 5V). Switching on the DigiOne Player in SPDIF is a real challenge: the reading of “Tamacun” Rodrigo y Gabriella or their cover of “Stairway to Heaven” appears as located between the speakers with a game of two guitars much more difficult to follow. No problems with timbres or dynamics (Aron Ottignon at the Funkhaus or “Man Down” by Vianney) just this aeration that is so obvious on Amber.
This aspect is all the more striking on the live Birdy and the title “Skinny Love”: the sound allows to transcribe in a realistic way the sound stage and the interaction with the public. The DigiOne, but we could also mention the Auralic Aris G2, cannot reproduce these different plans. Not that restitution is uncountable on these two products but we expect necessarily better. The reading of the cymbal game in the background of the “Wind will carry us” (recovery of Sophia Hunger) is much less immersive and jubilant on these last two devices (Allo DigiOne and Auralic Ariès G2) and despite some artifices of the G2 including at the level of filters.
Whatever the titles, this aeration appears as obvious and can raise the overall performance of this Amber to a level of the dCS Network Bridge. Is Amber better than the latter? The answer is not particularly on dense titles in terms of instruments and complex in terms of sound stage.
Regarding the different inputs, I must say that I perceived a slight difference between the AES and the SPDIF including the rising voices that tend to be slightly aggressive in configuration AES (Coincident cable and Synergistic Research CTS). This aggression was reduced by switching to SPDIF (Coincident and Mad Scientist). Is it linked to the outputs of Amber or the entries of my DAC … only additional tests will say (in progress). It was necessary to find a small flat to this product, but this point is in no way unacceptable seen from me as to the choice of this product.
Keep in mind that prices between an Amber and a Network Bridge vary from one to three, and achieving this level of performance at this price level can be considered a great feat. While it is not a “Swiss army knife” such as the Auralic Aris G2, but I retain from this essay, the various interactions with Metrum Acoustics that have always been open and willing to evolve the product of a point software and hardware. Metrum listens to its customers in particular by their desire to remain flexible in the features. For those who wish to go further (forgetting the warranty), this product is a nice base for optimization.
In conclusion, I would not have today a dCS Network Bridge at home, I think that the choice would be difficult between the dCS and Amber. In my configuration, this product meets 90% of my criteria (it lacks a USB output) and from a sound reproduction point of view it must be able here again to meet most of my expectations. In this sense, he is likely to stay at home on a second system oriented around listening to headphones during my insomnia attacks.
Regarding the rest, I will spend more time listening to different distributions on this device (PCP, Dietpi, …), shaping these distributions according to my needs (streaming Radio, Qobuz, UPnP, LMS, Roon , etc …) and my limited skills in Linux.