brucehuang55
If you have Raspberry Pi, hifiberry digi+ and external DAC, did you ever compare the sound quality output from (1) USB port to external DAC (2) digi+ coaxial to external DAC? The music source could be from web-radio or USB flash or HD? If the answer is Item (1), does that means there's no need to mount hifiberry digi+, just use raspberry pi and external DAC? Appreciate for your comments.
Discovery
I had these circumstances. There was no discernible difference. So I stopped using the digi+
brucehuang55
Hi Discovery
Same comment as you. Thanks for your sharing. However, I might just keep it mounted on Raspberry Pi because I would like to power Raspberry Pi from digi+'s P3 pin holes by linear power supply.
Stephane
Why would you want to put a linear power supply on an all digital combo (pi and digi+)?
Discovery
... because the electricity supply can make a noticeable improvement in sound quality to many hifi components. However, the Pi - being a very basic machine - doesn't benefit much from a LPS because the weaknesses are on the Pi itself, i.e. the voltage regulator. This splits the incoming 5v into 5v and 3.3v for different parts of the circuit. It's a very cheap component and its task can be improved by bypassing it.
A very easy way to see this is to supply 5v to GPIO pins 2 and 6, instead of to the micro-USB connector. The difference in sound quality is immediately apparent. If you go further and modify the Pi to accept 5v and 3.3v in the right places, the difference is even greater, but this requires good soldering and electronics skills.
It's detailed here:
#41411
Be advised that, whilst beneficial, this is experimental and you need to be careful to avoid damage to your Pi.
Stephane
That is total nonsense, the PI is digital, the stream to the digi is digital, the stream out of the digi is digital, how can a linear PSU improve sound ?
Discovery
I know it may sound difficult to take on board but there are often noticeable improvements to improving the quality of power supplies in hifi.
As an example, your approach might expect that all 'bit perfect' streamers output just zeroes and ones, so they would all sound the same? As the fact is they don't, you might realise there is more to it than just ones and zeroes... It would take a much longer reply to begin to explain it but there is accompanying interference that can affect the sound quality and, if removed, the sound is cleaner - as an analogy, think of the distraction of background chatter in a restaurant when you're trying to have a conversation across your table with a friend.
I, and several others, have modified our Pi's, as described in the linked article. We are enjoying better quality sound - that is a fact so is indisputable. It's up to you how you wish to rationalise that. I don't argue with what my ears hear.
I hope this helps.
Stephane
Please take the time to explain and if you have any papers or studies about this give me the references.
Discovery
With great respect Stephane, I'm going to decline. I'm happy to agree to disagree. I don't need convincing - you do. Google is your friend - do your own research and see what you find.
Regards,
Trevor
ianhaynes
I was skeptical too but there's a video on YouTube where Hans Beekhuyzen compares three PI power supplies.
https://www.youtube.com/watch?v=L_i8UTa4rw4
He mentions testing with a Bob Dylan track 'Man with the long gray coat' and could hear differences on this track with the three PSUs, with a linear PSU giving a cleaner rendition of Dylan's voice at the beginning of the track.
I tried this, comparing my standard Pi 2A switched mode wall wart and a old linear supply I had to hand. I could indeed hear the difference. I've now built a more modern linear supply and it's definitely better than the wall wart. The difference isn't massive but it's definitely there.
Ian
Stephane
I can admit that a good power supply (linear or not) can affect the analog part (DAC output stage) but how can it make the digital part any better ?
Discovery
Hi Ian,
"He mentions testing with a Bob Dylan track 'Man with the long gray coat".
I saw this report, and was intrigued to hear what Hans was describing. I felt it was a great song, and the whole album (Oh Mercy) is very good.
Discovery
Hi Stephane,
Research 'jitter'. It's not the whole answer, but it's a starting point.
Or visit one of us who has a modified power supply and let your ears decide.
brucehuang55
Appreciate all your comments, but seems to focus on the arguments on the sound improvement by the location where linear power supply powers to Pi or digi+. Is there any comment on my original problem "If you run Raspberry Pi with external USB DAC, no need to mount digi+ because of not much sound quality difference between music from USB port of Pi or coaxial of digi+ to DAC"
Discovery
Hi brucehuang55,
ls the USB port on your external DAC asynchronously controlled? If so, this favours the USB connection over a coax or optical connection so the Digi+ has no advantage.
This view was advised to me by the award-winning designer of my DAC.
brucehuang55
Hi Discovery,
According to the DAC manual, It says it takes the "XMOS asynchronous transfer solution". I just translate from Chinese. I am not sure if it is same as you said. Anyway for me, there's no much sound quality difference of the music from USB port of Pi or from digi+'s coaxial to my DAC. In this case, I might dismount digi+ and power Raspberry Pi from 2&6 GPIO pins by linear power supply. I'm not sure if it'll be better sound quality than power digi+'s P3 holes without dismounting digi+. Thanks.
Discovery
Make sure you get the polarity right - pin 2 is 5v, pin 6 is ground.
Let us know how you get on.
DomieMic65
As far as I know only quite old DACs are not "Asynchronous".
Also many people in local forum comment that the USB is preffered conection over the i2s/spdif of the Raspberry!
And a question about LPS.
As I understand it from the comments here and on the "3x PS" thread... is it prefferable to conect it to the GPIO than the mini USB port?
I am asking because I do not have the skils to modify the rpi board and I want a simpler solution!
Discovery
Hi DomieMic65,
Yes, those of us who have tried it have found that the Pi sounds better powering it through the GPIO pins than the mini USB port. Try it and decide for yourself. Then update us...
DomieMic65
Discovery wroteHi DomieMic65,
Yes, those of us who have tried it have found that the Pi sounds better powering it through the GPIO pins than the mini USB port. Try it and decide for yourself. Then update us...
Thank you very much!
