Testing Raspberry Pi with Digi+

[Grundgütiger]

For what it's worth I "tested" my Naim Unitiserve 2TB version against the Raspberry Pi 2 Model B with an attached audio board Digi+ transformer from HiFiberry (I switched off the volume control in RuneAudio's MPD settings). Both were connected directly to a pair of nuPro A-300 active speakers from Nubert (Germany) that claim to do a full digital signal processing. As I don't have an adapter for the Naim's electrical digital output it was connectid via Toslink to the loudspeakers, so the Raspberry's connection was with the electrical cable. I used mid-priced audio cables from Belkin. For the test I played David Bowie's "Space Oddity" album in its 2015 remastered version in FLAC 24/96 resolution. The Naim has an internal 2TB hard drive, the music for the Raspberry Pi came from an attached 1TB USB hard drive (no extra power supply). Both players were plugged into the loudspeakers, so all I needed to do was using the loudspeakers' remote control to switch between the electrical and the optical SPDIF input. There was nearly no switching gap between the source selections. To make an one hour listening and remote pressing session short: I couldn't hear a difference in sound quality between the Raspberry Pi set-up and the more than 20 times more expensive Naim Unitiserve. The only difference was with the volume: The Raspberry was much "louder" than the Naim. But other than that I was impressed. After a while of listening and pressing buttons I really forgot which signal was from which machine and I couldn't tell where it came from, even when I thought that Naim should bring the better quality.

After that I tested the Raspberry with both SPDIF cables, the electrical coax cable and the optical Toslink cable. Both were connected to the nuPros and again I could switch between both input signals. This time there was no difference in the volume and again, no difference in sound quality. So I couldn't confirm Hans Beekhuyzen's test on YouTube, who noticed a remarcable difference between the electrical and optical connection.

...

[Discovery]

Hi Grundgütiger,

FWIW, I was originally very aware of the difference between TOSLink output and S/PDIF output on the Digi+ (there was significantly fuller bass on S/PDIF - the TOSLink sounded 'thin' in comparison, and definitely missing something). However, on experimenting today, the difference has gone. Perhaps, there's a burn-in period for the board until it settles down and gives its best performance?

Regards,

Trevor

[Grundgütiger]

[HansBeekhuyzen]

I did a two piece video on DAC interfacing: https://youtu.be/AWM8fOCCVW4 for part 1. In short it comes down that when implemented perfectly, there is no difference when used within specs and in a perfectly set up set. But that's like stating that accidents are unnecessary if everyone would drive perfectly safe. It's true but apparently far from the reality of the day. Optical connections provide galvanic separation preventing ground loops but optical connectors are limited in bandwidth and can get polluted. Electrical connections can cause ground loops unless a decoupling transformer (like the ones on the HiFiBerry Digi+Transformer and the Audiosonics DigiPi+) are used. Electrical connections are also sensitive to tray magnetic fields (as around power cords) so you need not only use a cable that is 75Ω (for SPDIF) over a wide spectrum but also is shielded very well. AES/EBU needs 110Ω cabling and is slightly less sensitive to stray magnetic fields due to the symmetrical build up. Using shielded power cables or placing the power supply at least half a meter from the audio cables therefore good practice. If you everything wrong, setting only one thing right will not lead to noticeably better sound. Only when you took all measures mentioned above, and if your stereo is sescerning enough, you will hear clear differences. And if you don't give a damn, that's fine too. As long as you enjoy the music.

[rastus]

HansBeekhuyzen > Is this really you, Hans Beekhuyzen? Or someone just taking the piss...

PS: You sure write like Hans does. I've watched all your vids about the Pi's and added hat's, and read the 'scripts' (written words) of same on your web site. THANK you for doing them vids, great stuff.... and especially thanks for putting up the scripts. My goodness, the Internet is a fun old place.... never know who I might run across. Anyway man, thanks for all the hard work! Helped me, and many others too!