Sound quality comparison

[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: 3x-powersupply-for-rpi-t4141.html?hilit=pins%202#p18118

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.



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