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Could someone answer this question please,> The New Allo Boss 2 HAT Dac,
can it sit on top of the GPIO pins like the other ordinary hat DAC's such as the Piano and so forth, I was thinking of putting it on top of a RPi 3 in a clear plastic case. I have heard the BOSS 2 has a part that juts out, and in the way of the processor, so, have not heard anything otherwise, ie, I just want to use it as a straightforward HAT dac. Will it be OK with RPi 3??
AND, can it be powered by the same power source (I have a 3Amp 5 volt) that goes to the Pi? ie, does it have that power jumper thing that can be adjusted, or removed.?? Any info or advice would be appreciated. thanks. Edward.
Follow Ups:
Allo's documentation on the BOSS 2 isn't great IMHO. They offer the DAC with their own Acrylic case with OLED screen (you add the Pi) or the Player version can be purchased pre-assembled in a nice aluminum case.It doesn't appear that the Boss 2 can mount ON TOP of the Pi like a HAT. In the photos I've seen on the Allo website and elsewhere, it appears that the BOSS 2 is mounted to the side of the Raspberry Pi board rather than on top. This restricts you to using one of Allo's cases rather than a variety of standard cases on the market.
It can be powered with a single supply or separate supplies depending on a jumper setting.
That being said, it might still be a decent setup. I have the older Boss 1.2 DAC and it was OK for a secondary audio system. In my case I used it in the garage with powered speakers. However, there are much better sounding outboard DACs available.
A better sounding setup for Raspberry Pi 3 IMHO is to use the Allo SPDIF HAT (DigiOne) and run that out to an external DAC over coax. Or with the Raspberry Pi 4, just run USB out to your external USB DAC. USB in the Raspberry Pi 3 was not good. It is much improved in the Raspberry Pi 4.
My earlier version BOSS DAC HAT on top of RPI3
Supercap on bottom of BOSS DAC bumps up against heat sink on top of RPI3
The Allo Boss DAC (not the Boss2 version) supercap bumping the heatsink can be avoided by using an even lower profile heatsink or no heatsink at all and take your chances. On the other hand, the heatsink is electrically isolated so it's not like it shorts out to anything.
Edits: 10/07/21 10/07/21 10/07/21 10/07/21
The Allo Boss 2 is not a typical HAT.
It'll occupy the GPIO header, but sits side by side with the RPI motherboard.
IMO not very nice is that the DAC board still covers a small part of the RPI.
E.g. That'll make quality cooling a challenge.
Beside that you've got that control panel, which you can not detach and which covers the Wifi antenna. Therefore Allo recommends to us a Wifi dongle. Gee.
Let's not talk about that flimsy display.
And yes. You could power the whole thing with one supply. I think that Allo Nirvana would be a nice choice.
All in all, I'd never buy that device myself. A pity that they havn't managed to design a "real" Boss2 HAT. The current Boss 2 has nothing to do with the original. I was really disappointed when I saw it. (Over @DIY you find my feedback towards Allo.)
Enjoy.
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blog latest >> The Audio Streaming Series - tuning kit pCP
"A pity that they haven't managed to design a "real" Boss2 HAT."As I mentioned over a year ago, no one will ever produce an outstanding sounding HAT DAC for RPi because there is simply not enough PC board real estate on a HAT to use quality caps and other discrete active and passive components for high quality audio. They will ALWAYS be constrained by HAT size and limited in audio quality.
I think Allo made another DAC (Katana) but that abortion consisted of an unwieldy stack of HATs that was a totally botched mess - IMHO.
The Allo Katana DAC:
Edits: 10/07/21 10/07/21
You are wrong now, and you were wrong a year ago. ;)
I do think that they could have done better.
And the Boss1 wasn't a bad DAC, we shouldn't forget that.
My Khadas TB1, is a hybrid HAT/USB DAC, there'd be plenty of
space left on that device.
The KTB1 isn't much worse (in my config) than my tweaked Gustard.
Actually the stock Gustard A18 performed IMO worse then my slightly tweaked KTB1. It took me a lot of tweaking to get the Gustard where it is now.
For the HATs it is important to get them separately and properly powered You need a cap buffer or very short cable to your PS (such as Allo Shanti). You can't work with 5ft 5V DAC cables.
Isolation/reclockers HATs etc. can help if that functionality is not covered by the DAC HAT.
I haven't listened to the Boss2. I do believe it is not a bad device - soundwise.
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blog latest >> The Audio Streaming Series - tuning kit pCP
Well, maybe someone will magically break the straight-jacket constraints imposed by the tiny HAT form factor in producing a decent sounding DAC. I have the Boss 1.2 and it is OK for what it is but easily outclassed by several outboard DACs that I have had in my setup.
I wouldn't mind hearing the Boss2 DAC myself. At least it has a bit more PCB real estate so the designer isn't so confined in his component choices.
On a separate topic, I have a hunch that 5VDC just isn't enough for a good DAC. Call it intuition but it seems to me that more voltage, especially in the analog circuits, can make a big difference in dynamics and clarity. Every GOOD sounding DAC that I have owned ran larger internal power supplies or much more than 5VDC with an outboard power supply. Just a gut feeling I have about the power supply voltage. The Chord DAC I had was OK running just 5VDC but it couldn't match some others I've had with larger and higher voltage supplies. This seems to correlate with dynamics but it's just a gut feeling.
Look.
The 5V gets usually upscaled to meet the requirements of higher voltages in the output stages. So, It's not the 5V. It's the "upscaling" that makes the difference between DACs with higher "native" voltages.
Much more important is that you separate analog and digital supply rails.
And that you separate the RPI power rails from the audio device rails.
And these rails must be fed with very low ESR, low noise supply rails.
Low voltages and higher loads require a high transient response and transient recovery on the rails. Again, you won't achieve that with a 5ft 5V DC cable.
There are solutions:
https://www.audiophonics.fr/en/raspberry-pi-and-other-sbc-accessories/ian-canada-conditionerpi-ultra-capacitor-conditioner-board-for-raspberry-pi-p-14596.html
Now. 3/4 or more of a DAC footprint goes into the PS section, UI control section, (USB) interface and I/O section. Since a HAT doesn't really need most of it the footprint of a HAT is IMO more than sufficient
for a high quality DAC layout .
And if you really need more real estate you add a piggy-back-HAT.
The main issue with highest quality HATs is the tiny addressable market.
That's why there's very limited progress.
Low/medium quality, low cost stuff like HifiBerry can address a
much wider market. The seems to work nicely.
That's one reason why Allo replaced its Katana (which was a major disaster - quality wise - I have one of them around ) rather quickly with the Revolution DAC. Simply to address a wider market.
I do also think that the Allo Boss2-streamer will not be a success. It's basically a very inflexible product and comes with certain weak spots.
And it's also not that cheap if you add up the entire BoM. It'll address a tiny niche market.
Anyhow. As long as you (Abe) simply keep swapping commercial DACs every other month all that is gonna be none of your business anyhow. ;)
Enjoy.
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blog latest >> The Audio Streaming Series - tuning kit pCP
"The 5V gets usually upscaled to meet the requirements of higher voltages in the output stages."
Which DACs do this? The Boss DAC HAT certainly doesn't do this. And if the 5V DC is 'upscaled' as you say, how do you think this is accomplished?
"Now. 3/4 or more of a DAC footprint goes into the PS section, UI control section, (USB) interface and I/O section. Since a HAT doesn't really need most of it the footprint of a HAT is IMO more than sufficient for a high quality DAC layout."
Possibly but I'm not convinced. I've had a few DACs and even if you remove the power supply and input board, the DAC chips and analog section are still several times larger than a tiny RPi HAT. My main point here is that there's not enough space on a HAT to accommodate high quality discrete active components and passive parts for the analog stage and the DAC. ALL of these parts need to fit on that tiny HAT.
"And if you really need more real estate you add a piggy-back-HAT."
And look what happened with the Allo Katana DAC. It was a stacked mess of RPi HATs with quality problems. Yes, there's a limited market for these things because no one wants a kludged together stack of HAT boards.
Sure, they're fun to play with but in the end, I don't think the form factor constraints warrant serious consideration in producing a good sounding DAC.
My current DAC is Huge compared to the others I've Owned. The Dual Power Supplies take up a substantial amount of room. The difference in Sound Quality was Immediate and undeniable between my Gustard X26 Pro and any DACs of the Dozen I've Auditioned in my place.
The Katana does DC/DC conversion for its Class-A stage. ;)
Anyhow. The PI4 improved heavily on the USB side, for me reason enough
to get back to USB DACs and to forget about HATs. The audio HAT evolution is pretty much dead for quite a while now. It's a pity, since most of these USB DACs still require heavy USB tweaking to get the flaws under control. With an I2S HAT all that USB audio nightmare was gone at least.
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blog latest >> The Audio Streaming Series - tuning kit pCP
" The Katana does DC/DC conversion for its Class-A stage."And DC/DC conversion means a switching circuit much like a switching power supply, pretty much defeating the reason for using a linear power supply as the main source supply. ;-)
I like the RPi4 as a streamer but not so much as a platform for a HAT DAC. As you said, USB is much improved on the RPi4 negating the need for a SPDIF HAT like the Allo DigiOne. I drive my USB DAC directly off my RPi4 USB port and it performs very nicely.
P.S. Stupid FAN in my Argon ONE case started to develop bearing noise so I removed the FAN entirely and reinstalled fresh thermal pads between a couple RPi4 chips and the case. It still runs surprisingly cool. I like the Argon ONE case because it allows access to ALL RPi4 I/O connectors and power from the back of the case.
Edits: 10/08/21
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