Review | Allo Revolution DAC, Part 1

PART I:  REVOLUTION COME, REVOLUTION GO

“On account of bad weather, German revolution took place in music”
(Kurt Tucholsky , 1890 - 1935, Die Weltbühne, 22.04.1930, Nr. 17 ) 

The Oxford English Dictionary (OED) suggests about 26 meanings encapsulated for a dozen definitions of the word  revolution, n. (rɛvəˈl(j)uːʃən).  Given the fact they do neither mention music nor computer audio,  we may want to select definition III. 6b.) instead when it comes to the  REVOLUTION DAC by Allo:

"An instance of great change or alteration in affairs or in some particular thing."

1. Allo & THE REVOLUTION

This REVOLUTION DAC was announced in MAY 2019 on DIY Audio and since then you could observe the expectations of the audiophiles who care about DACs costing less than $500. You could see the curious calls for reviews coming in at the end of last year and the pressure for this REVOLUTION was rising.

Designating an importance implicating moniker like "REVOLUTION" to a sub $300 digital to analog converter sounds like a bold move. However, it is also a sign of confidence, continuously won over the last years, when Allo moved from telecom equipment towards DIY Audio. The company now offers selected "Plug and Play" products on their website, which shows an astonishing complete set of more than 30 audio products. Allo says two years ago audio overcame telecom as a major driver for the tri-continental company, which was founded in Vancouver / Canada where the HQ still resides. Research and manufacturing happen in Bangalore / India, while development, distribution and customer service is located in Toulouse / France. Still, they are a small company by SME definition. Despite not being a boutique manufacturer they are a hands-on player in a very competitive low budget market segment of audio between DIY audio parts, accessories and ready-made audio units like streamers, amps or DACs. 

You may consider a challenge with the question: Is that really high-end audio? My response: High-end  is not defined by price alone.

The price/performance ratio of Allo products is first class. Engineering is excellent and sound quality has convinced many AS followers. If performance for the money is considered one important aspect when it comes to audio products, some of the Allo products we are discussing here on Audiophile Style can be wholeheartedly be called high-end, even if they aren't high priced boutique equipment.

Just to dial in some reality: when I talk to my eldest child, who loves gaming much more than Music, I can hear that a 600 bucks GPU can't be considered high end in his opinion. Subsequently, when I read his messages on my screen feed by an 8 year old GPU for then 100$ and my next PC is cornered around an APU solution he wasn't impressed at all.

However, an RPI and a suiting DAC are “too High End” for him for music processing. About the REVOLUTION DAC he told me: "too pricey although it has quite a lovely name."

When it comes to products from Allo we may note the famous DigiONE (Signature), the KATANA, BOSS and PIANO DACs, the Sparky or the Kali ReClocker. In Spring 2019 they announced 4 new products in their development pipe: the SHANTI LPS, the NIRVANA SMPS, the USB bridge SIG and the REVOLUTION DAC, which is the centre of interest for this review.

Again, a bold move and a lot to shoulder for a small player like Allo. Nevertheless, we've seen the arrival of the first three products during the year prior June 2020, and now the REVOLUTION is here. We should recall that this all happened despite COVID19 interrupting international logistics and supply chains since March 2020 and undeterred by the fact that companies and employees were facing lockdowns almost everywhere in the world.

"You say you got a real solution
Well, you know - We'd all love to see the plan"
(Morgan James - Revolution 1 - orig. The Beatles)

The REVOLUTION is the latest project in production, not because of lesser importance for their product range but for the need of minuscule, precise and time consuming development steps in the product's maturing process. Allo is committed to a high quality standard which indicative of the term REVOLUTION.

The REVOLUTION is a USB only DAC based on the ESS 9038q2m SABRE32 reference chip technology that ships for 286 USD to the USA and for 290 Euro into the European Union.

It's implemented on an Allo PCB board and benefits from the experience and the ideas of the Allo design team plus valuable input which they received during the development phase. Beside an exceptionally well measured THD+N of -114.5dB and THD performance at up to -124db on unbalanced RCA output, the DAC enables the user to manipulate the chip's THD compensation logic, meaning that you can choose between different 2nd and 3rd harmonics settings for perceived euphonic sq improvements, which in turn impacts the measurable THD/THD+N values diversely. For most DACs usually a low level chip function access and a voicing by design sounds more like the industry standard.

Combining both - the objectively measurable performance and subjective great perception - seems to be the rationale why the unit was called REVOLUTION.

According to the manual the Revolution offers

• 7 OS filters
• Oversampling function (OSF) bypass
• choice of sync/async mode for jitter reduction
• 2nd/3rd harmonics selection (8-step)
• multi-stepped Pop control, which works only in OSF mode

These settings can be changed manually using the mini-joystick at the front, whose functionality is mirrored on the optional remote control ($7.00) that integrates the volume control and a mute button. 

The REVOLUTION converts PCM signals up to 705.6 kHz and DSD up to octuple-rate DSD (DSD512). Like most HiFi equipment the DAC is said to perform best with a proper power supply - Allo offers the SHANTI LPS ($159) and the NIRVANA SMPS ($59) as bundle choices - and was reviewed conjointly with the  NIRVANA and the optional remote control at 355 USD (shipped). 

"Come so far yeah,
So just let me know when we get there if we get there"
(Fink - Sort of Revolution)

2 DESIGNER'S Q&A WITH IOAN B. FROM Allo

Allo in general:

Q: Is it fair to say that your company is divided into three different entities on three different continents/countries. (HQ/Canada - Development/Distribution/France, - Development/Production/India)?

A: Yes, that’s correct.

Q: Has DIY Audio already replaced Telecoms as the main line of business?

A: About 2 years ago, audio took over and became our main business.

Something personal:

Q: IOAN, who are you & what is your role in the Allo organization?

A: I am the architect of all Allo audio designs and I work with our team in Bangalore to refine it first then to do PCB placement and to test every power rail (CRO , Spectrum analyzer and Audio Precision ). In the same time, we send a few samples to 3-4 testers for audio quality …so we test both THD+N and sound quality.

 
Developers brainchild:

Q: Could you please explain the developer's idea about the product in not more than 5 sentences?

A: A competitively priced DAC that has great THD+N numbers ( jitter etc) and also sounds great….it's not the same thing.

Q: There had been major changes from the product announced in 2019 and the real REVOLUTION 2020. Which changes would you describe as the ones with major impact?

A: As far as changes…we constantly take readings in each power rail (and we have about 50) and we tweak components until we get a very quiet rail. (lowering noise)

Q: Which are the allo.com engineering components/competences that were used for enhancing the ESS9038Q2m DAC chip's performance? (i.e. Reclocking, Caps, Op Amps, Filter)?

A: We used a 6 layers PCB then we used LDOs on every rail. More importantly, Revolution has 2 clocks so it can apply the correct clock to the  2 major sample rates. At last Rev is using about 8 supercaps , so in fact you are “listening “ to audio delivered by one of the purest forms of electricity .

Q: Did you overcome the commonly known "ESS THD Hump"? And how did you do so?

A: Yes we did , it's about Op Amp feedback caps value.

Q: How important is the power supply to the REVOLUTION DAC performance?
 

A: It's always important . No matter how many filters we have (or LDOs) it seems to me that once noise reaches the PCB , it somehow changes the output. The funny thing is that I am unable to see it on THD+N numbers.

THD/THD+N:

Q: Could you provide some insight about your vision regarding THD/THD+N vs. perceived sound quality?

A: Once you reach a certain level of THD+N (and I would argue for -110) no further SQ improvements can be had using THD as a guide. Further SQ improvement can be reached by tweaking the analog stage, ... clocks and more.

Q: I'd like to ask  about the THD+N and THD values for the Revolution:

A: Latest tech data taken with AP555 shows THD+N at -117 % from 0-20 Khz at 90Khz bandwidth (higher bandwidth shows ultrasonic not included in a 20Khz)I will have the new data available in about 3-4 weeks when I can use a new machine from AP India.

THD (through 6th harmonic) less than  -130 !!! %, 2.2 Vrms, 20 Hz – 20 kHz, unity gain

Q: And could you provide a short explanation for the non-engineer why the results per channel are showing  0dB to appr. -10dB differences in your measurement data?

A: It's normal for any DAC to show a difference on harmonics depending on the channel . 

ESS 9038q2m

Q: In which setting the Revolution's 9038q2m chip plays in what ESS calls "DSD phase mode" aka "Native DSD", "DSD direct mode" or "DSD bypass" (AKM)?

A: DSD playback is not affected by any settings…aka you cannot change how DSD is played

Q: As ESS offers - according to its datasheet - two DSD modes for the ESS9038q2m, which one you've chosen: "DSD normal mode" or "DSD phase mode"?

A: They are both “Native DSD” . It's not possible to choose one vs. another in the DAC register. There is no control. At page 51 you will see that in fact they seem to be both the same , on phase mode,  one complimentary data is ignored.

Q: Does OSF bypass leave the PCM bit stream unaltered as well inside the revolution?

A: OSF is bypassed…my understanding is that 8x oversampling is removed…
 

Q: Does the OSM bypass mode, as a consequence, have effects on the volume settings?
 

A: Yes as per manual OSF bypass will remove volume control.

Q: How many filters are provided for the REVOLUTION?
 

A: The REVOLUTION has implemented 7 User configurable filter settings.

USB only:

Q: What would be the technical reason to deploy USB only?

A: It’s a very mature interface and it's convenient.

Q: Can we expect an upgraded version with balanced design/output and more input variability from allo.com in the future? Something like a SIGNATURE REVOLUTION ?

A: Yes but at a different price point.

Q: You will finally pursue a route for USB power with an split USB/Power cable, that "will change the REVOLUTION in a pure USB DAC"?

A: (It is) Not yet in stock, it will take a while, China manufacturing is very slow and uneven nowadays.

Firmware upgrade:

Q: Do you permanently refine the firmware (XMOS and Thesycon) and how does the customer receive notice about the newest (stable) firmware?

A: Yes we will keep upgrading the firmware . We will add something on the web page to show the latest firmware.

Q: To my understanding, the upgrading process is simultaneously as well the way of providing the change of firmware?

A: It’s a firmware change

Q: You provide drivers for LINUX and WINDOWS, however, no information for Apple devices is officially available (at the time of asking).

A:  Mac is native DSD 256 and Linux us also native up to DSD 512 (no driver)

Q: Is it correct that the device XMOS firmware is driverless supported by Apple and in accordance with Apple's USB 2.0 implementation, and that it is able to play 24/192 PCM and up to DSD256 when fed from Apple devices? 

A: Yes

Q: What happens for APPLE users if the device comes with Thesycon firmware ? Does the user then need to connect to either a Linux or a Windows machine to change/enable/upgrade to XMOS firmware? Pls excuse and correct any misconceptions, I am not an Apple guy ....

A: Thesycon firmware is Mac compatible. No change. At this point we don’t have a document on how to flash the firmware using a MAC pc.

Q:  At that point I need to ask: Are you thinking about a solution regarding a less complex process for the Firmware change?

A: Firmware upgrade is not made by us but by Thysecon (Germany) . As such we have no control

Q: What is the possibly perceived difference of the two firmwares, objectively and subjectively ?

A:  None for me.

Thank you, Ioan !!!

"At every corner of the city at every stone
where the wind blows Revolution"
(Gianna Nannini - Revolution)

4 REVIEW SETUP

Due to my belief in the value of comparative reviews, I considered from the start, focusing on two ways of comparing the Allo Revolution:

First, I'd compare the device in standard setting against two popular DACs in the audiophile community which I own and know well. Both, the Khadas Tone Board DAC (KTBD) and iFi Micro iDSD BL have had their proper review here at Audiophile Style and they offer their owners a big bang for the budget.

About the iFi I wrote in 2017: "The BL, playing music up-sampled to DSD512, in my system and with my ears,  gives more grip and flesh to the low end, is delicately nice to the upper midst without softening, but profits from a good yet not enormous soundstage and the darkest background I have heard so far in my system. The placement and presence of instruments are very special and I tend to think the sound is clear, not bright but muscular and dynamic".

The KTBD also got some praise, especially for its clarity. Separation and dynamics are beyond price level, however this implementation can be perceived as fatiguing (too bright) in some cases.

Second, I want to explore more specifically the audible differences because of changes in sync/async mode, OSF bypass , filter selection and changing of 2nd/3rd order harmonics values.

For these reasons I used two different setups:

1) I have retired my NAS for the summertime (today we have again 100.4°F, not for the first time this year) as a first step to keep my office climate below 30 degrees C. I am using my old CAPS ZUMA build (ASUS Q87/16Gbyte/Audiophile optimized Win 10 Pro/Roon) as a ROON server and local storage machine in conjunction with Qobuz. It is connected to a Netgear 108t switch, as are the Gentoo flavored RPI 4/4Gb which is using the ROON Bridge endpoint software and the MOON ACE that serves as an pre/poweramp fed by the REVOLUTION's output signal into one of its two analogue inputs.

All other DACs for comparison were likewise fit to the Moon's analogue stage and fed by the RPI4's USB output. The Revolution got powered by the $59 Allo NIRVANA SMPS. The Pi alternately by an iFi 5v SMPS or by the 5v output of the HDPLEX 100w LPS. I exchanged NIRVANA and HDPLEX power feed between REVOLUTION and RPi several times for comparison but couldn't notice perceptible changes. The speakers are B&W 805s, the pair of subwoofers you'll find in my profile weren't in use.

2) The critical listening setup associates the RPi powered by iFi 5v SMPS, the Allo Revolution DAC powered by the Allo NIRVANA SMPS, the JDS Labs ATOM amp and the Focal Elegia Headphones.

The PCM files were provided by Qobuz mostly through streaming or taken from the local SSD at the ZUMA. The Revolution was left in the default settings for DAC comparison:

Sync mode, no OSF bypass , filter selection (3) and no changing of 2nd/3rd (1/8) order harmonics values. The device was always grounded with the Nirvana SMPS .

"It looks, It feels, It moves, It sounds, It smells
like a revolution
Well I don't care what you heard
This is more than just a word
(Calvin Russell - Like a Revolution)

5 REVOLUTION PLAYLIST

In the weeks before I have received the REVOLUTION I have started to created an open Qobuz playlist called "REVOLUTION PLAYLIST" which you find under: https://play.qobuz.com/playlist/3459177

Please feel free to attach your personal favorite songs about REVOLUTION to that playlist. I have selected a dozen of these songs for my critical listening plus some that weren't available with the streaming service. Especially more Classical and Jazz tracks would be greatly appreciated. 

"Don't you know
They're talkin' 'bout a revolution
It sounds like a whisper"
(Tracy Chapman - Talkin' Bout A Revolution)

6 PREVIEW

I decided in accordance with Chris to cut the review in 2 parts, as my neighbors started to cut, for several days, their hedge row in front of my listening room. This made it difficult to find time and space for finishing the critical listening sessions.

Quick executive summary :

I compared the KDTB and the iFi Micro iDSD BL to the Revolution, listening to some selected tracks from the REVOLUTION PLAYLIST starting with the native bitrates, then upsampled to 192kHz, to 384kHz,  to DSD256 and finally into DSD512. The details will consequently be found in the 2nd part of the review not only deals with the critical listening sessions.

The KTBD - within its limits - doesn't need to hide against the REV/iFi when it comes to SQ vs. price correlation, while there is a distinctive SQ difference in favor of the latter ones when it comes to 1:1 comparison. The major differences apart from the listening fatigue which is undeniably underrepresented with the iFi and the REVOLUTION are soundstage (width and depth), blacker background (iFi) and delicious details (REVOLUTION). The iFi to my ears shows more maturity by  punching a bit harder with - in my perception - less clarity, where the REVOLUTION impresses with details, width of soundstage and a certain depth & articulation I began to admire by heart.

The next part will offer inside shots of the device, a detailed analysis of the revolutionary & critical listening session with selected music from the REVOLUTION PLAYLIST. A run-through concerning the firmware change, a reflection on the Achilles' heel of USB Audio and finally you'll get a verdict with the pros & cons of that REVOLUTION device.

Community Star Ratings and Reviews

I encourage those who have experience with theAllo Revolution DAC to leave a star rating and quick review on our new Polestar platform.

Product Information:

• Allo Revolution DAC ($259)
• Allo Revolution Product Page
• Allo Revolution User Manual (172KB PDF)
• Allo Revolution Test Data (1.2MB PDF)

Where to Buy

• Allo.com