HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

First success for the new power supply. I've used a USB Type A (the big flat one) plug. I noticed on the USB connector that there appeared to be power rails from the top to the board mount, so I figured it would be possible to use a large external usb drive since it would get it's power from my psu and not from the Pi board. Well that seems to work. Of course it means that all the USB connections are now used up (so there's no room for a wifi dongle, for instanct. I'll try it on my newer, four usb port model and see it if works on that.

I'll give the PSU a bit more time to run in and them I'll try a number of variations on the power supply side:

1. Walwart PSU vs my PSU
2. Walwart in BMU vs my PSU
3. My PSU in BMU

If I haven't driven myself mad by then, I may even dig out the TFS.

Terry - don't know if you've seen this, it's a discussion about noise being introduced into the Pi from the Ethernet link (grounding connection in cable). Possible influences on the Hifiberry analogue output. The solution they offer is to input via Wifi. Does not affect Hifiberry Digi's though.

http://www.crazy-audio.com/2013/10/trac ... pberry-pi/

Interesting but so far as I can see what they are saying is the noise is the result of grounding from the shielding of the Ethernet cable.

Most Ethernet cable used is utp (unshielded twisted pair) not stp (shielded twisted pair). (Mine is utp.)

I've tried wifi and couldn't get the bandwidth in the setup I used (ripped CDs skipped and high res files hardly played at all). But I do have one HiFiBerry which I control using wifi with the music on a usb stick.

Also not sure if this applies to your generation of pi (which is supposed to have a better power supply).

I have made the mistake of combining two experiments. I wanted to see if I could get a large usb powered external disk working with my power supply and it does (in fact it appears to work with just the wall wart) but this does seem to have an impact on the sound quality. This rather negated what I've been trying to do which was to see if the new Power supply impacted sound quality.

I think I have UTP cabling. And the Digi models don't seem to have any problems here, mine has the extra galvanic shielding transformer for noise protection on the coax output.

Does the USB power system take wattage away from the Pi processor?

You could also load music files directly onto the microSD chip. I've got a 32Gb card in there which the
Pi seems to be happy with, although I haven't tried that yet.

You probably do have utp cabling. STP cabling is typically used outside of a building (e.g. to link up to an external radio link).

I read somewhere that the Old Pi couldn't run an external USB HDD because of the power the HDD took - I'm doubting that now.

I've not tried loading music files onto the SD card. I discounted that because of the size of filestore I have.

OK. In the blue corner I have a Raspberry Pi B/HifiBerry Dac with wall wart power supply and Super Sound Pipe and in the red corner and identical PiB/HifiBerry Dac with my MkII power supply plugged into the BMU and Sound Pipe. Both plugged into the P90. Both have Volumio 1.55 on the SD Card newly written today.

When I've done this sort of thing before, I've been trying to compare DAC boards and came to the conclusion that any difference I heard was probably down to the difference in cables.

This time there is, after my first session, I think a clear difference.

The wall wart powered Pie sounds OK - well that's which I've been living with for some time now and have thought that it sounds good. But the MkII PSU/BMU powered one is more musical.

I've just been playing some of Pletnev/Mozart Piano Concerto 20 in D Minor on both and switching between the two. With the MkII PSU/BMU there's just more musical detail: I think I hear more subtle dynamics within short phrases of music; Pletnev's playing is smoother and the notes a little more defined; the piano sounds more like a piano; the timing and interplay with the orchestra is more comprehensible; there's a little more separate between the various instrumental voices; and more of a sense of space and depth in the sound. All of which adds up to it sounding like more emotion is being conveyed through the music.

Looks like a clear win for the improved power supply PSU/BMU. Are the USB drives still causing any trouble?

Next stop - Durio?

Still some listening to do, I think. The differences aren't so marked on other music sources.
USB problems resolved but that's out of the when at the moment.

Terry, have you tried i/c other way round? Would that make margin bigger towards diy psu?

Another stupid question

Could the improved power supply have a built-in BMU? I mean, one item wouldn't need the humungous transformer that is in the pukka BMU would it? One smaller transformer supplying another?

The above is possibly nonsense, since the transformers I work with have a +ve, -ve and centre '0' on the secondaries! Oh Gawd, I wish I really knew what I'm on about here