HiFiBerry Digi+ Works Best on RCA...!

[Discovery]

Hi All,

I bought the HifiBerry Digi+ board for my RP2 as a bit of an experiment. I tried the optical output into my DAC because I was cautious about the USB output from the Pi. Anyway, swapping between these two sources on my DAC showed no material difference.

It never occurred to me to test the RCA connection...

Today, I saw a video by technology journalist Hans Beekhuyzen on the HiFiBerry website, He tested an RPI2 with Digi+ board running Runeaudio. He outputs it to a Chord Hugo DAC (see https://youtu.be/DmeUxk14vCc or https://www.hifiberry.com/news/). He goes into some detail about the USB concerns, hence his configuration with the Digi+. He found the optical link wasn't nearly as good as the RCA output, which gave a noticeable difference in bass response compared with the other two options. Naturally, I couldn't wait to try it on my own system. He's right! It goes so much deeper now with lovely smooth, controlled bass.

Hans tested the Digi+ with the dedicated output transformer (the version I have) which benefits from galvanic isolation from the electrical output.

If you have a Digi+ board and haven't tried the RCA output, give it a try and see what you think. I'd be astonished if you didn't smile.

Regards,

Trevor

[Surson]

Hi Trevor,

I also purchased a Hifiberry Digi+ board, but unfortunately the board looks dead (not recognized by Rune Audio), so I couldn't test it... I'm waiting for a solution for my board, but my plan was to use the optical output. Do you know why there is a significant difference between optical and coaxial liaison? (both should be pure digital outputs, and both are isolated if you have the version with transformer). By the way I will test both if I can get a new board and let you know if I can heard an audible difference...

Cheers.

[rastus]

I seen Hans' you-tube review; I also read the transcript of the review (http://thehbproject.com/en/reviews/162/ ... -RuneAudio). I am running Rune Audio on a Raspberry Pi 2 with a HiFiBerry Digi+ into a Yamaha RX-V2065 AVR (built in Burr-Brown DACs). I tried both the optical (SPDIF on Toslink) and coax (SPDIF on RCA, 75Ω cable) connections to feed the Yamaha. After spending hours today listening to music (mp3's and 44.1-192 kHz FLAC's) and switching between optical and coax I must say I don't hear any difference between the two connections. What I will say is, both optical and coax sound great fed through the Yamaha. Maybe the brand and type of coax cable used has an impact on sound quality (as Han's suggests and confirms in his review).

Surson > RuneAudio does not by default recognise the Digi+ card, you have to edit the config.txt file and add the following line:

dtoverlay=hifiberry-digi

Sorry if I've trod on anyone's toes, long time lurker here, first time poster.

[hondagx35]

[Surson]

[Discovery]

I'm really surprised the same difference hasn't been seen. I experienced exactly what the reviewer experienced - much deeper bass.

I'm running my Pi into an Audiolab MDAC, into a Quad 909 power amp then out to Quad 989 Electrostatic speakers. I knew the 989s were capable of good bass but the difference was immediately apparent - almost too much at first, but I've acclimatised nicely.

I was using an RCA cable of unknown origin I had in my collection but for a few pounds have since upgraded to a Van Damme cable and have downloaded the test track used in the review, that was suggested to have sibilance problems. The new cable is better in this regard than the non-descript original.

As someone mentioned, I, too, assumed the optical and S/PDIF output would be identical but they simply aren't (in my case, as per reviewer).

I might get my microphone and run a trace on REW to show the room frequencies being generated from each output (USB, Optical, S/PDIF) to measure the different bass levels achieved.

[HansBeekhuyzen]

To help out here a bit: I didnot listen to the optical output since I know that it, at best, is equal but most likely be less than the RCA output. This is due to bandwidth limitations of the optical TosLink connection. The difference in sound was between RCA out and USB. The result with USB will differ depending on a number of factors and since the Digi+ board is very affordable and very good, I consider that to be a better option. The audibility of jitter, that is the cause of the difference, will vary greatly amongst audio sets. Partly because some d/a-converters handle jitter better than others but also partly because high end sets (my set 1 is around € 20.000) have far higher resolution than more affordable sets.

[Mat]

This makes me really curious about difference between Optical and RCA output of HifiBerry digi+. Since HansBeekhuyzen did not try Optical output I guess there could be reason in DAC? It has to have different electronic for Optical and RCA input since signal is different.

Unfortunately I can't try RCA output since I have only Optical input in my DAC (active speakers) but makes me wonder if there is difference on other DACs too?

[HansBeekhuyzen]

The signal on RCA is amplified and fed to the TOSLink connector but since the TOSLink connector has less bandwidth the square waves that represent the ones and zeros are more distorted. See https://youtu.be/grzoqEb2KMk for an explanation on what goes wrong. And don't forget: the worst type of interface might perform best if the implementation of the other interface is very bad. Further more ground loops can distort the digital signal in electric connections as where optical connections do not suffer from ground loops (or high frequency interference due to electro magnetic strays).

[Surson]

Hi,

I just received a new working board from hifiberry (thanks to them!), I tried both coax and toslink, but to be honest my ears can't make a noticeable difference. Maybe I had to wait some hours for cable warming (just jocking).