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PostPosted: Fri Feb 17 2017 00:43
by michelangelo
As you know, since Allo stepped into the SBC related audio scene, they proved to be a constant source of satisfaction. So, when they told me they had a new "Master DAC" under works, well, I just wanted to listen to it.
The time has come and now I have their latest BOSS DAC playing with Volumio in my system.

So, what does "Master DAC" mean? Basically, a master DAC does not take the clock from the PI itself but rather uses a separate clock (oscillators, 2 are needed, one for 22hz and 24hz and their multiples). This is nothing particularly fancy, as almost any I2S DAC uses this approach.
The clever bits of their design comes from the fact that they added some clever stuff under the hood:

- 3 different power rails, with individual filtering. One for the DAC chip itself and the digital side, one for the analog stage and one for the oscillators. On paper, this should translate with very very low noise floor and better clock accuracy
- Film capacitors on the output stage to reduce distortion, coupled with a super-capacitor to enhance bass representation
- Good oscillators

Allo suggests at least 50 hours of break-in before critical listening (I guess the super capacitor is the reason they suggest this). I'm not deeply concerned of burn in generally, but I left it playing music for a couple of days before listening to it, just in case.

By listening to it, seems that Allo did it again. If we want to make it short, I love how it sounds. The bass is punchy and present but yet very controlled. This is the best bass I've heard from any I2S DAC.
That does not mean this DAC has a "dark" sound signature since it delivers a balanced reproduction.
Another very evident feature is that its dead silent. There is no noise whatsoever, therefore dynamics and detail are really standing out. And I mean it: the instrumental separation and level of detail is one of the best I've ever heard.
As for its sound signature, I think its very neutral, just with a little more bass than you would expect. Which for me, is a good thing.
Acoustic guitars and bass guitars are just fantastic with the BOSS.

To give you some comparisons, I think this can be considered a Kali + Piano on steroids: it has the same sound signature, with a bit more bass, details and overall balance but a bit less focused stereo image.

Last, my personal favorite feature of this DAC is that it delivers an engaging musical representation. I found myself repeatedly beating my foot following the rhythm of the music, and
I got really involved in the emotional part of music during my listenings. I know some of you might think I'm talking audiophile's bullshit, but this part of the musical message
for me is quite important and recognizable. Mark Wheeler from TNT, can surely describe such phenomenon better than me, and he calls it PRaT ( ).
Altough this term was introduced in the good old days of turntables, it describes quite well the ability of a system to foster appreciation and enjoyment of music.
And the BOSS does exactly that.

Allo, bravi!

The playlist of the test

Bob Dylan - Blowing in the Wind
Waldeck - Get Up.. Carmen
Metronomy - The look
Red Hot Chilli Peppers - I could have lied
Rodriguez - Sugar man
Rino Gaetano - Cogli la mia rosa d'amore
Alabama Shakes - Don't wanna fight
The Alan Parsons Project - Mammagamma
Whomadewho - Every minute alone
Led Zeppelin - Since I've been loving you
Pink Floyd - One of these days
Sebastian Tellier - La ritournelle
The Offspring - Pay the man
Tom Waits - Clap Hands
The Beatles - I want you (she's so heavy)
The Rapture - In the grace of your love

Re: ALLO Boss

PostPosted: Fri Feb 17 2017 06:55
by marcellom
Great Michelangelo, great review. The Boss seems a "must have" Dac. I like basses in rock music.. but in classical music too. Have you try to listen something like Orff's Carmina Burana or similar?
Anyway... ill wait for the next super hiend DAC from Allo...
Great job Allo, and tnx Michelangelo :)


PostPosted: Fri Feb 17 2017 08:29
by Olivier
The new Boss dac work with volumio ? If yes what is it the choice dac ?
Thank in advance


PostPosted: Fri Feb 17 2017 08:52
by allo
Thx you Michelangelo for your review.

I would like to add a few things on the BOSS.

First , all review units have a small problem. On the last RC filter (analog signal) we made a mistake and instead of having the cutoff frequency at 100Khz (out of human hearing) we have it at 15Khz (0-20Khz is human hearing)...we are correcting that in mass production units.

Michelangelo, if you liked the review unit, I think you will love the mass production one. Anyway we will try to send you asap a second unit.

Our design goal with BOSS was very simple. Implement the best PCM51xx in analog. Ask the important is the DAC IC vs implementation.

First we looked at jitter. By placing the NDK oscillators a few cm from TI dac ic , we reduced the jitter from ps (Kali) to femtoseconds. Second we added the supercapacitor. You see , low frequency (bass) needs a lot of power and with a capacitor that has 0.2F (yes 0.2Farad) that power is now available. Everyone talks about "bass booster" or some other way of bass cheating...but the simple truth is that power/electrons = bass. Boss has the real deal.

Third we looked at capacitors in the analog path. Instead of using cheap ceramics we are using PPS film. Only very hi end dacs use PPS capacitors (film capacitors don't distort the analog signal like ceramics) fact the big film capacitor (fancy looking one ) you see on the dac costs as much as the DAC Ic itself.

In the end the second question still stands . Take our BOSS , with one of the best implementation of the TI IC and compare it with hiend dacs (Ess Sabre , AKM) and tell us: Is the implementation or the brand of the DAC ic thats important.

No matter what your answer is , enjoy the Boss at 59$. Like Michelangelo says , it will make you dance.

Re: ALLO Boss

PostPosted: Fri Feb 17 2017 09:15
by marcellom
The important is not the brand....but what my ears like :)


PostPosted: Fri Feb 17 2017 09:53
by Saiyato
Wow now I am curious, I was leaning towards trying the piano 2.1 + kali setup, but I might take on this setup first (also because it fits the budget better obviously).

According to the site we are one week away from mass production availability :). This new design eliminates the need for the reclocker right? Because of the different approach?

@Michelangelo, I too am curious which DAC model should be chosen for the BOSS, but then again I might be a tad bit unpatient. ;)

Great work guys and great write-up!


PostPosted: Fri Feb 17 2017 10:28
by allo
Boss has its own clocks...its like a reclocker + dac


PostPosted: Mon Feb 20 2017 13:15
by Saiyato
allo wrote:Boss has its own clocks...its like a reclocker + dac

Thanks! I'll be waiting for availability, is there a case available too upon launch? :)


PostPosted: Tue Feb 21 2017 02:35
by stunta
@michelangelo, this is what Allo said about the Boss on another thread.

allo wrote:Seems like a good choice. If you have already Kali + Pianos (or some other slave DAC) it might not be worth to buy the BOSS.

It would be good to support your subjective findings with objective measurements. That way your post does not look like a paid advertisement, which I am sure its not ;)


PostPosted: Wed Feb 22 2017 18:06
by RDaneel
@Michelangelo: the Allo Boss Dac requires a new driver in the Linux kernel: the current image available for the download already contains it? It is more than two months old, so I think you will have to release a new Volumio image?

Furthermore I read that two lines must be changed in the /boot/config.txt file:

Code: Select all

Will we need to manually add them, or will they automatically set by Volumio?