Review 1/2: Allo DigiOne Transport

Allo DigiOne Transport Review


What it is, and what it’s not:

The DigiOne is essentially a sound card for a Raspberry Pi computer. The Raspberry Pi has a built-in sound card but the sound quality is not nearly acceptable for even a beginner computer audiophile. It has timing issues, power issues and noise issues to name a few. But the rest of the Raspberry Pi is great for building a low powered networked audio player that brings your high quality lossless music files to your audio system, with lots of online resources and help forums.

So why don’t we just plug in an external USB DAC into the Pi and be done with it? Because, the Pi has a hardware limitation where the USB ports and the network adaptors (LAN and WiFi) shares the same communication bus. This just means that there is not enough bandwidth to receive and send the music data between the network and the USB DAC at the same time for very high-resolution files. Typically, 24bit/192khz files and up starts to have issues where the music starts to make snap crackle and pop noises. In some cases when the Pi CPU was under load I got issues from 24bit/96khz.

The solution is to use an add-on board that plugs directly into the GPIO header of the Pi. This board (like the DigiOne) connects directly to the I2S (Inter-IC Sound) interface that is a separate data bus from USB. Now you can receive the music files over USB, LAN or WiFi and send the output to the I2S interface essentially eliminating this mentioned bottleneck. What makes the DigiOne special is that it has a “dirty” region that receives the noisy power and data signals from the Raspberry Pi, cleans it up with various kinds of high quality electronics, reclocks the digital audio signal, and sends it over to a “clean” region where the jitter and electronic noise figures are measured and published at 0.6ps and 50uV respectively. And this is achieved with using a switch mode power supply. This essentially means that you get a super clean digital signal ready for the DAC to receive. The DigiOne only produces digital audio out in the form BNC and RCA S/PDIF signals. Allo also produces another product, the USBridge, which does the same, but also provides a super clean USB connection.

In summary, what the DigiOne does is to provide your existing external high-end DAC with a super clean S/PDIF signal, with the music source file ideally received over the network or from a USB hard drive connected to the Raspberry Pi. You can see it as a replacement device for your CD player.

What it does not do, is convert the digital signals to analog audio ready for your hi-fi amplifier. In other words, it has no DAC function. It just transports music to your DAC.

How I got hold of it – the customer’s experience:

While reading about the Allo DigiOne on various forums, I noticed a few trends. The majority of the guys says it sounds very good. They replace their existing Raspberry Pi-based transports and mini computers with the Allo DigiOne. They use ordinary power supplies and still get better results, while other guys who use linear power supplies report marginal or no improvements. The other trend is that whenever someone had issues, the Allo team responded immediately, helping them out with replacement units or whatever assistance they needed.

I therefore decided to contact Allo directly to find out how I can get my hands on a DigiOne Transport board for my Raspberry Pi. Andre responded the same day, assuring me that even though they could help me directly, they recommend I avoid shipping and customs issues by ordering from PiShop.co.za , who is their local authorized distributor in South Africa. He said “Rest assured that they will handle any issues you may have in the same professional manner that we would”. I also asked Andre a few very technical questions, which he answered. He even put me in contact with one of their engineers for the ones he could not answer. Excellent!

When I contacted the PiShop, they informed me that they would order their Allo stock within 2 weeks, and would contact me when it arrived. They advised me to place my order on the website. I indicated that I wanted 2x DigiOne Player Kits, one for me and one for a friend. The kit consists of a Raspberry Pi 3, a Allo DigiOne add-on board, Allo Power Supply, SD Card and a very nice laser cut acrylic enclosure. The kit costs slightly less than the individual parts.

After just more than a month after my first enquiry and a couple of update requests, the order arrived at my office. The kits were perfect, complete and well packed. However, a few other parts that I ordered on behalf of friends were incorrect. My initial efforts to have these parts exchanged were initially met with little to no support, to my frustration. Eventually, after a quick call to the PiShop, Johan Burger, one of the directors, stepped in and quickly sorted out the mess. I was impressed with his service and the lengths at which he went to fix the relationship.

Looking back, I can wholeheartedly recommend dealing with Allo.com (Andre) and PiShop.co.za (Johan). They look after their customers.

Here are some detailed pics of the kit and parts used:

Assembly and Setup:

The assembly was like building some fancy Lego Technic or Meccano toys. Very satisfying! You are also done before it gets boring. See pictures below:

The difficult part is to decide which software you want to use. I can only recommend two systems that work out of the box for me. The first is PiCorePlayer that works with a Logitech Media Server (LMS) system and converts your RaspberryPi into a Squeezebox. The ideal would be to have a separate LMS machine somewhere on the network and with the PiCorePlayer as an endpoint, similar to the very popular Roon system. PiCorePlayer also allows you to run the LMS system on the same RaspberryPi if you want to use only a single device (not tested by me). The second is Volumio, which is a standalone Music Player Daemon (MPD) based system, a fully functioning standalone player that can use local or networked storage for storing and playing your media. Volumio might at first feel slow, but keep in mind that it takes a lot of processing to index your media library on the Raspberry Pi, etc. If you added a massive music repository, leave it over night to settle down and index. The Volumio interface looks beautiful and makes up for some performance issues. Both systems sound great. I had the best functional results with PiCorePlayer. Here are some pictures of the Volumio interface on a web browser and on the Android app:


Both systems install with ease, following the same basic steps. In short you download the system image of choice and write it to the SD Card you got with the kit or already have. Then simply insert it into the Pi, power it up and wait a few minutes. Usually the system starts up and do the basic setup for you. You then connect to it with any web browser or applicable app on any device on your local network. I recommend using a network cable connection to the Pi for the first-time setup and configuration. Setup your WiFi and then remove the network cable. The full instructions should be on the website of the system you chose.

A word of advice: if you intend to use WiFi as main connection to your Raspberry Pi, but you do not have excellent WiFi reception or your Pi is not located very close to the router, do not assume the Raspberry Pi 3 built in WiFi wil be adequate. In fact, it is shockingly bad. I had reception issues 2m from my router with no obstructions in between. I think it has to do with the extra Allo DigiOne board on top of the Pi, which interferes with the signals. If you want reliable WiFi connetion, get a USB WiFi dongle. Solves lots of problems and headaches. I can recommend the Edimax EW-7811Un nano USB dongle or the Edimax EW-7612UAn USB dongle with antenna, both available from RS Components SA. I specifically tested these two dongles and they work beautifully.

My listening setup:

I have a networked Media PC hosting all my music and movies, running Windows 10 with PLEX and LMS installed. It is tucked away under my staircase where its cooling fans and spinning hard drives can make serious noise without bothering anyone. At my desk in another room I have the Schiit Modi Multibit DAC, the Schiit Magni 2 Uber headphone amp, the Raspberry Pi DigiOne Player and a nice pair of Audeze EL8 open back headphones.

The Multibit DAC has 3 inputs. USB, COAX and TosLink (optical). As explained in the introduction, my computer is hooked up to the USB input, and my trusty Chromecast Audio is connected to the optical input of the DAC. The DigiOne Player feeds my Multibit DAC via COAX. To switch between the inputs is a push of a button on the DAC. The Schiit components both have the stock Schiit supplied linear power supplies, and the Raspberry Pi with DigiOne uses the Allo provided switching mode power supply. An interesting remark is that all 3 power supplies comes from the exact same OEM supplier, Xing Yuan Electronics, just different specs and model numbers.

I compared the different options by playing the same song over all the inputs at the same time and then switching between them. This took weeks… It was difficult to pin point the differences. Even if you could hear they sound different, you couldn’t immediately say what the difference was or which sounded better.

How does it sound:

The Allo DigiOne combined with the Multibit DAC sounds fantastic. In order of preference on the Multibit DAC I would say COAX first, then USB, then optical. Or is it USB first…? I can honestly say that to me there was almost zero difference between USB (fed from my desktop PC) and COAX on my DAC. Now and again I almost believed there was something different, and then I would revisit it later and not be able to hear it. So I can’t say there is a difference with clear conviction. Optical sounded slightly more closed in and not so transparent as the other two. But if you have to take the cost of this optical source into account vs the USB and COAX sources, you can’t knock the optical input as it is still ridiculously close to the others.

I can now go and try to define the sound qualities by using all kinds of audiophile phrases that is totally subjective and misleading. All I can say is the music sounds like it should. It sounds like my Schiit Stack I am used to and nothing different. That just means that the new COAX source is doing the right things and doing it very well at an affordable price. 

Now, switching the USB input to feed from the Raspberry Pi is a different story. The DigiOne sound is for sure better than using the USB directly from the Pi. You hear those random pops and crackles very clearly (though I usually had to listen for about a half a minute to identify a clear pop), almost like the sounds a wood fire makes. These sounds are gone over the DigiOne output on the same Raspberry Pi. Take for instance the Tundra track from Amber Rubarth’s Sessions from the 17th Ward album that has lots of quiet pieces with loud percussions and echoes and some feint sounds coming from outside the building from the street. Turning up my amp a bit more, there was a slight but distinct hiss over USB from the Raspberry Pi, which is not there when you switch to the DigiOne. I could make out more details from the ambient sounds over the DigiOne than directly from the USB as the noise flushes over them. I have to also add that I used another exact same Raspberry Pi for USB input with the exact same power supply than the DigiOne, and thus the only difference is having the DigiOne on the one unit.

I found a glitch!

When you introduce any power spikes or dips to your DigiOne setup, the DigiOne stops working! Everything responds as it should, there is just no sound produced. To fix it, you simply soft reboot the Raspberry Pi and all is well again. No need to power cycle. This is super annoying! Apparently the DigiOne is super sensitive to sudden power spikes/dips as the designers were overprotective with the circuitry. This is probably a good thing for longevity of the device. I have posted this issue on the Volumio Forum and there are now two solutions to this. See https://volumio.org/forum/allo-digione-sound-after-cable-change-amp-switch-t7729.html.

Allo very kindly offered to exchange customer’s original units for a factory-modified DigiOne. So just keep this in mind when you decide to order and want yours already modified. This issue was particularly painful when you leave the DigiOne Player switched on, and switch off your amplifier or DAC, or change Coax cables, or change between BNC and RCA connector to hear differences and do comparisons. Some users have reported a similar issue when switching on lights on the same mains circuit.

Conclusion:

The most common DAC inputs are USB, Coax and Optical. To me there are pros and cons to all. This is my take on the 3 options, bearing costs in mind, and also not pairing with outrageous super high-end DACs and amplifiers, and headphones or speakers. Also bear in mind that the Modi Multibit DAC is limited to 24Bit/192khz.

For USB input, you need to spend some more money on a source computer, like at least an ODRIOD with proper USB implementation and faster CPU, maybe the Allo USBridge, a laptop computer, or some Apple device. But you need clean power and preferable no moving parts and noise. This could become expensive. You can also easily run into USB driver issues. You will probably have lots more processing power for DSD decoding on these devices. You can use a Raspberry Pi, but I really think you are missing out on super high-resolution files and DSD for instance. If you just have Redbook quality music and don’t care much for details, sure, try the standard Raspberry Pi, but at least upgrade the crappy power supply to a linear power supply to try and get rid of most of the noise. Lots of info on this online.

For Optical S/PDIF, you will be hard pressed to find something more user friendly, simple, efficient and CHEAP than a Chromecast Audio. Sure, there are other things available that might be cheaper, but try configuring and managing streaming services from the comfort of your seat on your phone with super-fast interface response times. I had a WD-Live Player, Mede8er, PlayStation and some other things with optical output. They are slow and suck against the Chromecasts. I also don’t think if you use an optical source that you are seeking super high-fidelity sound. Optical is limited to 192khz and seems to have lost of jitter by design due to conversions to and from optical apparently. But it is electrically isolated from the source that can be handy when you have lots of noise from ground loops etc.

For COAX RCA S/PDIF, I think the DigiOne is a winner. It uses a cheap Raspberry Pi as base. It can use a cheap power supply as it cleans up the nasties nicely by itself. The sound quality is as good as USB on similar equipment. It is dead quiet, generating no distracting ambient noise. OK, COAX is limited to 192khz as well, but it is less prone to jitter. If you can clean the electrical noise (and the DigiOne does) this is the better S/PDIF connection for your trusty external DAC. There are other add-on boards for the Pi you can try out, but reviews pointed me towards the DigiOne as overall better sounding than the direct competition. It is more expensive as well, but not by so much. It’s easy to setup and looks stunning on the desk or in a rack.

I now use all of the above inputs connected at the same time and it provides me absolute joy! I can have great PC sound over USB for YouTube, games and music while I work, usually using closed back headphones. For dedicated high-resolution music listening, in a quiet environment with open back headphones, I switch to the DigiOne Player over Coax. For multi room audio and background music using streaming services etc. over desktop speakers, I use the Chromecast Audio over the optical connection. I think I have found a very nice and versatile setup feeding my headphones and desktop speakers. I think that if I upgrade my Schiit Stack later, I will still keep the current digital sources as is.

The DigiOne is a keeper and a very welcome addition to my collection of audio gear.

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