Allo DIgiOne review

I have been playing with the DigiOne with almost a month now, and I’ve been able to listen to it with a variety of DACs I do know well.
I’ve never been a huge fan of S/PDIF interface, and I always preferred to use good old USB or I2S when it comes to PI. This is because I believe that shorter the signal path, the better (as you might know from my earlier posts).

Nevertheless, I decided to free my mind from the above prejudice and use an analytical approach with the DigiOne. So, my first step was trying to understand why Allo released an S/PDIF transport that costs about 3 times than similar gear: I know them too better to think they are overpricing, or adding useless components to their boards, so I was curious to see the rationale behind their choice.
Just from a visual inspection you will immediately notice that this board is literally filled with components. I was just wondering why all this stuff for S/PDIF…

From what I’ve understood Allo’s design is based on 3 principles:

  • Completely discard the shitty Raspberry Pi clock, and instead use the DigiOne as a “Master DAC”. By doing so the clock (crucial for the time-domain musical message) will be way better than what the Raspberry PI can offer. This is achieved by placing 2 high quality clocks.
  • Clean the Power supply coming from the raspberry PI through hi performances DC regulators and filtering capacitors. As always, the cleaner the power is, better the musical outcomes (Signal to noise ratio).
  • Isolate each stage of the signal path: there is a galvanic isolator separating the Raspberry PI from the clocks, and the clocks themselves are isolated from the WM8805 (which is the S/PDIF transmitter).

Allo themselves quote that the DigiOne, in fact, is “a master codec with digital/electrical/ground isolation from RPI AND wm8805 and a reclocker”.

I definitely see the advantage of setting the DigiOne as a master clock and cleaning Power Supply as much as possible (which has been a tradition by Allo since the Kali, and IMHO this should be a precondition of every good audio product). I, however, do understand less the advantage of galvanic isolation with S/PDIF, but this is just my lack of knowledge.

So, on paper we have for sure the best implementation of an S/PDIF transport shield (no-one has master clocks, PSU cleaning, re-clocking and galvanic isolation altogether). But how will it sound?

I tried it on 3 “good enough” DACs, which I usually use connected via USB, in order to compare the outcome of the total chain.
I was impressed: never thought S/PDIF could sound that good. My previous experiences were with other shields and there is a very evident difference. Especially for the things I do care about: detail, soundstage and musicality.

Basically, for me at least, the DigiOne has become the only S/PDIF source that I would have in my system. I find the same level of enjoyment that I do have with the Mini86 and ipurifier (on the same DAC, but connected with its XMOS based USB receiver). I won’t be making any further comparison because it will be like comparing apple and oranges (the implementation of the USB Receiver and S/PDIF receiver of the same DAC can be of different quality level).

So, sonically speaking, well done Allo: this is the only S/PDIF I managed to actually like.

Now, what I don’t like about this. I would have preferred to have a way to feed the DigiOne and the Pi separately. Allo claims there is no need (and they are probably right, considering the DC regulators and galvanic isolation) but I think this is anyway a Nice to have feature.
Then a side note, we got various reports (and I was not able to re-create that situation in my system, or just did not notice) that on some systems, when changing sample rate, the first bits of a songs were not being played. Allo quantifies the delay from 25 to 250ms. Considering this happens only when you change sample rate, and it might be solved in future software updates (given is not an hardware limitation), this is just a minor issue.

So my conclusion is: the DigiOne is expensive when compared to similar solution, but it’s definitely worth every penny of it. What we have here is something that was not designed to sound good, but to sound as best as possible (on Raspberry PI), and this is not yet another case of over-engineering: they made clear design choices which my listening impressions confirm to be correct.

To me, the DigiOne (or DigiOne Player, if you look for a complete player) are the best choice possible as of now if you own an S/PDIF DAC, or if you know for sure that the implementation of S/PDIF receiver in your DAC is superior than the USB side.

Again, and I start to repeat myself here, bravo Allo!

So which are your favorite tracks to evaluate these characteristics? Thx.

Hi michelangelo,

Thank’s for your review.
But little precision. In digital world, SNR have no place (almost…). SNR is for analog part. Yes, you must have a good power supply, the only thing is to not have signal perturbation to high. I ever see lot of digital circuit running well with -6db of noise. In digital world this is binary : 1 or 0.

For this particular card. Yes, all the job is made by the WM8805. Because it is use as a Master clock. 95% of the job is to have a regular clean clock to elapse the flow of data.
There is no galvanic isolation but digital isolator. This is not the same. To make this possible, Allo use plenty of LDO. A good DC/DC regulator (LT3042) is use for clean powering the WM8805.

Galvanic isolation would have been the best solution for coupling the card with DAC (floating circuit, non interference distribution), but the choice is to use digital isolation. Normal, it miss some space and will give some jitters problem. In this choice, your are electrical coupled with the DAC. So, if you don’t want to send some noise to your DAC, you must take a particular attention to have a clean signal to send without pollute the other part. It is why the power stage is so developed on all part of the card.

Thank’s for your review, thank’s for Allo for this good card !

Ludo.

The output stage is galvanically isolated from WM8805 and RPI.

We are using digital isolators for signal and DC/DC isolated convertor to power the next stage (and then we clean it with filters and LDOs). So we have 2 isolated grounds ( dirty and clean ground)

Hi Allo,

I’m just found a hidef picture of the card and i can now clearly see the 2 separation of grounding on each part of the Si8641 Digital Isolators.
I also see the DC/DC converter between the two ground plan.

But my question is : Why did you put the WM8805 to the nasty part of the card ?

Generally we put digital isolator on I2s signal (between I2S output of the Pi and the input of the WM8805) to have all components on proper side of the card, WM8805 is a sensitive part.
The clock will appreciate to be much closer of this IC without crossing the Si8641.
But the goal is reached, we have a galvanic separation between the noisy Pi and the outside DAC.

Ludo.

Simple. Even WM8805 is noisy. On the clean side we keep the absolute minimum components . The clock (has to be on clean side) , buffer and flipflops.

So basically you have the SPIDIF signal passing the barrier. Of course it will get some jitter (digital isolators add jitter)

What we do, its recloaking the signal with a very clean mclk. So your spidif signal has now the MCLK jitter (measured at about 0.4ps)

Hello i bought the digione to test against digi +pro.
I would like to know what are the power pins from the rpi that feed the digione.
I m using shunt regulator on digi pro separated from pi and this was a big improvement.
So i will bend rpi pins and feed my power supply to the digione. Just need to know the pin numbers.
Tks

Enviado do meu SM-J500F através de Tapatalk

Hello ,

Digiones takes the 5V pins from RPI (not 3.3V)

Ok thank you. I will test it normal…before all.
After i will feed my shunt regulator 5v to digione only to see if it has a big difference.

This comparison looks very interesting. Please share your impressions with us.

I have been using the DigiOne for a few days now. Running 2.203 (2.246 doesn’t boot).
Volumio still crashes (root filesystem or boot records get munged). Reminage the SD, and good to go.

Previous tried to PiFi spdif. Which was a horrible, sounded as bad as SqueezeBox Touch.

The bit stream is converted using old reference dCS Ring DAC (Delius/Purcell). These are
extremely musical when fed by my Goldmund 36 transport.

So how good is the DigiOne against a reference transport?

Pretty good (provided the files are on the a local fast access USB key). The DigiOne has
a little more more bass and better bass resolution (SPDIF via RCA). But it still suffers from
some digital haze. The Goldmund (via AES/EBU) sound are softer, more laid back, less fatigue.

Toss up, trading less fatigue for a little more bass. The deal kicker is Volumio and 1200+ hours
of music at my finger tips from the tablet or phone. And my transport can only deliver a
RED BOOK 16/44 bitstream to the DACs. DigiOne can get me 24/196.

This is the closest I have come in 5 years to a FLAC delivery solution that rivals a good
CD transport.

The price for performance is insane. At $99, it is essentially free. (Joke, a pair of WBT RCA
connectors cost more and they don’t even make the sound better!)

Many thanks for sharing your impressions.
Have you made some comparison with the USB output too? In my tests, the USB output of the Raspberry (and of the Raspberry only; on a x86 PC it sounds good) sounds bad.

I will test against a reference transport too in this case an 3000 $ arcam from a friend that sounded better than hb digi pro but not for a large margin

I don’t own a USB dac yet. The dCS (Delius/Purcell) are from 15 years old. I haven’t found a need
yet to move up.

I am just very happy to find a transport (in this case, almost free) that can deliver almost what I
get off my transport. Previously, I had to cut CDs from my FLACs to enjoy the music. With DigiOne,
the hassle is gone. 8)))

If I get bored, I will grab an Allo Boss and see how it compare. I have Piano 2.1 without Kali - use in
the bedroom. For laughs, I put in on my mains feeding the AR Ref1/Ref75SE/ESL-988. It doesn’t
fair well against the dDCS. It really needs Kali for a fair comparison.

The only reason for me to go USB is for sourcing > 24/192 data stream. Most of the music I listen
to is ancient. Recorded on tapes in the 50s and 60s. The recent REDBOOK 16/44 remasters
are still extracting more information that I hear the improvements over the last remasters.

I am beginning to see 24/96 remasters from DG, but it will be a while before they go to 24/176
or even higher. A good SPDIF will keep me happy for some time to come.

Listening for 2 days… digione is good… but similar to hifiberry digi pro with a good power supply.
But i need to test more time.
Sounds thinner in my system than hb digi pro with external power supply.
Digione needs burn in period?

What power supply are you recommending?

Yes. It will improve more at about 50h of burn in.

PSU should not make a difference since we have our own DC/DC isolated PSU on board.

However reality is that PSU does make a difference because of interaction with the rest of your system. We recommend a good PSU (low noise output low noise to the mains)

Hello… i m very impressed… the sound has been improved after some hours…
Instaled diet pi … great sound i think is better than max2play… but i have to listen more…

Allo did a very good board… sounds very very good… i have to test with ext power supply to see if can improve further.
Thks for bringing good products …
Finaly i m listening to music…not computer sounds…