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My new Boss - another PI-HAT
My new Boss - another PI-HAT
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Old 19th February 2017, 08:15 AM   #1
soundcheck is offline soundcheck  Germany
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Join Date: Mar 2005
Location: DUS
Default My new Boss - another PI-HAT

Hi folks.

Allo provided me - free of charge - with their newest HAT-DAC - "The Boss".
It's based on the TI PCM5122 DAC.
The same chip as used on the HifiBerry DAC+ Pro.

"Free of charge" though is not exact what it is. I had to spent hours
to get their driver integrated and updated.
And it still had some minor flaws. (Which are resolved by now)
And. Allo did not expect me to write this up!!! Just to make that clear.

Beside that the drivers still doesn't support 354k8 and 384k samplerates!!!
Consequence: There's no way to bypass the internal DAC filters!

Not sure why I did spent all that work.
Perhaps I just got bored since my Sabre9023 HAT-DAC performs extremely well since weeks.

I actually told Allo first - I'm not interested, since I don't like the PCM5122
DAC (based on my HifiBerry DAC+ Pro experience) .

What changed my mind, was a 2nd glance at the DAC.
Inmate "cdsgames" (from Allo) is sneaking around for quite some time.
He's been collecting quite some ingredients over here to end up with a promising recipe. That became obvious.

If you look at the MamboBerry or HifiBerry thread, you realize that most mods follow the recipe : clean and fast power is key.

The MamboBerry could IMO be considered one of the best HAT-DAC solutions, if not the best, during those days.
The Boss IMO tops all that by a large margin.
Allo e.g. uses 3 LT3042 LDOs to power analog, digital and clock voltages.
I think, you can't do better then that. They also apply extensive filtering in front of it.

They also put a special focus on the clocks, clock lines and clocking scheme.
E.g. The HifiBerry DAC+ Pro is facing serious interference with the PI (Wifi).

Allo did that much better.

From what understand they even buffer the clocks.

Another top feature is a super-cap for the analog voltage pins.
Yep. They've done their homework.

All DACs I tried benefited from having their own supply. That's where Allo
fails. They don't offer that option. It would require HW modifications to accomplish this. That's IMO a NoGo. However. The question would be if
a 2nd supply would even be required for the Boss. If the Boss would
get along with a single supply solution, that'd be another strong selling/buying point.

The external power jack that could be used after a modification (removing a resistor) though, would IMO be on the wrong side of the board.
And it's not a very common format. As I told you Dear Allo, there's IMO some homework to be done if you ever consider a Boss REV2!!!

Now. How does it sound!?!?

I've been using a single iPower, a PI3, and my own OS btw. And I'm still on my testsystem (Adam A5X)

It sounds good. Really good. Lot's of (lowl-level) detail and very clean. I've had a hard time to pin any flaws.
I'd even doubt that Kali would make a relevant difference.
Very nice.

I'd say. For now it's the best "stock" HAT-DAC I had in my hands.
Considering the parts list, the current price tag is IMO more than fair.
Modification cost might not even pop up. Playing around with boutique LDOs is IMO not required.
That'll save you a lot.

I'd still would have to integrate the DAC into my main system to come to a final conclusion though.

To summarize the weak spots for now:

1. Driver availability
The DAC requires a custom driver which is still not widely available
2. Lack of 384k and 354k8 support because of driver
3. No separate power option.
4. Modifications almost impossible (tiny parts) - but probably not needed anyhow

Bottom line.

Well done Allo.

Great to see the progress in the HAT-DAC arena.

Enjoy.

PS: I already prepared the kernels and drivers for Moode Audio. It's up to Tim to release them.
Attached Images
File Type: jpg AlloBoss.jpg (906.4 KB, 1993 views)

Last edited by soundcheck; 19th February 2017 at 08:30 AM.
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Old 19th February 2017, 09:01 PM   #2
hopkins is offline hopkins  France
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Thanks and very interested in this DAC.
Here is another interesting review : https://community.roonlabs.com/t/all...eview/20575/12
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Old 20th February 2017, 01:04 AM   #3
ZacharyP is offline ZacharyP  United States
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Well done soundcheck, and congratulations to Allo on a great product.
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Old 20th February 2017, 06:20 AM   #4
soundcheck is offline soundcheck  Germany
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They did have a problem with the output filter!!

Make sure that you get the updated version of the DAC!
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Old 20th February 2017, 07:45 AM   #5
soundcheck is offline soundcheck  Germany
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Just had a look at the Boss review on roonlabs.

In fact - interesting.

But obviously there are different opinions out there what's actually better.

Kali/Piano or Boss. Some also consider Boss to be the winner.

Nobody seems to mention what DSP settings are used on the
PCM5122. And these IMO do make a difference.
OS and OS setup also make a difference btw!

Non of them had 354k8 or 384k working.


And then there's still the output filter issue.

Obviously the DAC needs a couple of days break-in.

Some other points just crossed my mind.

The Piano might get cleaner power from the Kali.
The Boss gets the mess straight from the Pi.
The Kali also must be considered a RFI/EMI shield for the DAC btw!
There might be differences.


However.

I mentioned before, that I'm not really a fan of these PCM51xx DACs.

My highly tweaked Sabre ES9023, with the Kali feeding synchronous I2S
and separate PS sounds just great and very natural (right choice of caps!).
No upsampling required!

To be honest. I feel absolutely no pressure to get it replaced by the Boss.
To be fair I should at least give it a try.

The Audiophonics 9018 solution IMO comes with certain weaknesses, just by looking at it. (opamp output stage, asynch clocking, average power scheme, ...)
There are many people out there who prefer a well implemented 9023 over a 9018. I don't feel the slightest temptation to order that AudioPhonics DAC.

However.

I suggested towards Allo to build & sell a very stripped down ES9023 plus Kali combo in I2S sync mode (no local DAC clock).
They'd just take a LT3042 - it needs just one - apply the same filtering and power/decoupling/buffer scheme and they'd be set.
Beside that all the 5122 I2C clock handling (complex drivers) and that DSP nonsense would be gone.
And. They should not forget an external powering option again!

Let see how things are developing.

Enjoy.

Last edited by soundcheck; 20th February 2017 at 08:09 AM.
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Old 20th February 2017, 11:09 AM   #6
ZacharyP is offline ZacharyP  United States
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Quote:
Originally Posted by soundcheck View Post
They did have a problem with the output filter!!

Make sure that you get the updated version of the DAC!
I'm just waiting on them to ship out the updated version to me for testing
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Old 20th February 2017, 12:42 PM   #7
cdsgames is offline cdsgames  Canada
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Thx Soundcheck for your review and for integrating with Moode.

Your points and advice were noted. Like you correctly said , we designed this DAC as a good entry point for people to join the revolution that its happening right now with streamed music based on RPIs.

For the esssabre 9023 , its definitely something that we are interested in. We are just finalizing the Kali 2 (lower pricing) so it will be a perfect compliment .

One question, did you modify yourself the RC filter ? In your pics I see the 15Khz one..
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Old 20th February 2017, 01:08 PM   #8
soundcheck is offline soundcheck  Germany
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No. I did not modify the filter.
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Old 21st February 2017, 08:17 AM   #9
cdsgames is offline cdsgames  Canada
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With the correct filter there is a bump in SQ. We will send the units with corrected LPF shortly. The last resistor on the PCB (next to RCA )has to be changed from 470R to 75-100R with 75R being better.
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Old 21st February 2017, 09:48 AM   #10
soundcheck is offline soundcheck  Germany
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On my MamboBerry I bypassed that resistor altogether.
The Sabre datasheet expects a 0R anyhow.
And the amp does some HF filtering.

Bottom line.

The best resistor is no resistor (in the signal path).
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