JustBoom Raspberry Pi Digi HAT

I currently use Volumio on a Raspberry Pi 3 which is connected to a Denon PMA-50 via USB (type A to B). In my opinion the sound quality is pretty good, though I’m certainly not an expert. I’m curious what kind of quality improvement (if any) I could expect by connecting the Pi 3 to the Denon amplifier via an optical/coaxial cable by using the JustBoom Raspberry Pi Digi HAT or a smiliar product. Any opinions are greatly appreciated.


I would not recommend the optical connexion. For the price of a good interconnect, better to invest in a DAC HAT like the Boss or the Justboom and go analog to the Denon.


Dominique T

If you are playing hires flac, i would recommend a coaxial cable 24bit/192khz instead of the optical 24/96.

Thanks guys, but you didn’t really answer my question. The question is not whether to use coaxial or optical, but rather if I could expect any quality gain by replacing the USB connection with a DIGI HAT. Besides, why would you send an analog signal to the Denon (which is capable of receiving a digtal signal)? I don’t see at all how this could improve the quality.

How is the sound getting to the amp? Via USB.
In that case is the Pi actually using the Denon as the sound card.
I have not seen the USB used to just pass audio.

If this is the case then I don’t think you would get any improvement. If the Denon is the DAC that is.

On the RPi, anything that moves stuff away from USB is going to be an improvement. The whole Ethernet/USB portion of the RPi is run by a single chip and if you’re trying to move stuff into the RPi via any form of networking, it’s going to reduce the amount of time available for USB. By going coax over a SP/DIF I2S card, you’re going to get the best out of the RPi. Whether this makes any perceptible difference is down to the rest of the chain (interlinks, speakers, soft furnishings etc.) but at least you’re not overloading the RPi…

Chris M

Another thought occurs; have a look at the difference between the Justboom stuff and the HiFiBerry Digi+ Pro. HFB claim that their improved clocking reduces jitter better, meaning more accurate music. Allo do something like it as well…

Chris M

Thanks Chris, that’s some helpful advice! Any thoughts why you would use coaxial? Logically speaking Optical (toslink) makes the most sense to me as there is no danger of electrical interference, but then I couldn’t really claim I hear the difference.

Optical has, because of its working principle, more jitter than coaxial (electric). That’s why Allo for instance just got rid of the optical connection on its Digi One.

i) Whether or not you can hear a difference depends on the rest of your setup, your ears, …
ii) As you’ve already pointed out, coaxial has the disadvantage of electrical interference.
iii) That’s why coaxial output often has galvanic isolation. But for that to work, your DAC unit has to be grounded. Otherwise there can be transmission errors…