RPi3 / Screen / HiFiBerry Dac+ Pro Questions

[Fenric77]

Hi All,

I'm relatively new the the RPI but am really enjoying the experience, and recently bought HiFiBerry Dac+ Pro. I have mounted my RPi3 on the official 7inch touchscreen, then mounted the Dac+ Pro on top.

I am currently powering the RPi, the Screen and the DAC using the official RPi 5v power supply. I have powered the DAC by soldering the red and black wires to to the first and fourth pins (Like this: but soldered on, rather than jumpers. ) I have updated config.txt and the DAC is now playing music beautifully through OpenElec/Kodi (I'll explore other Music player solutions later - just used Kodi as i already had a working copy install).

I would now like to improve sound quality by removing the R14 resistorr and power the analogue circuits on the DAC using a battery back recommended on another forum (liner PSU is too expensive at this early stage) -

I have four questions (apologies for my newbie ignorance) (if you can only help with one or two of them, I'd appreciate anything you can advice me!) :

1. When the online guides to performing this upgrade to the Dac+ Pro says 'connect your external 5V power supply to the pin header P3 (left GND, right +5V)', does this mean solder the wires onto the metal the edge of the hole? I'm new to soldering but when soldering the red and whtie wires to power the DAC, there were posts to connect them to, and I just want to check if it's the same when there's only a hole.

2. I currently have the DAC, screen and PI powered by an official RPi 5v power supply, connected to the micro USB socket on the RPi (and using the jumper cables mentioned above). If i carry out this modification to power the the DAc's analogue circuits from the battery pack with my power arranged in this way, will I actually be bypasing using he USB power supply for the analgue circuits as I intend?

3. I am playing my music as Wavs from a 4tb USB drive powerered solely from the USB socket on the RPi (and it powers and plays fine, currently), will I get better sound quality and/or remove USB interference (as well as reducing problems from power-drain on the RPi power supply) if i connect a double USB lead to the 4tb drive? The power connected could also go into the battery pack, whilst the data connected still going into the RPi? Or would this make no difference to sound (or power-drain, as the systems is currently working fine with the RPi powering the HD?)

4. Finally. when I'm soldering wires from the battery pack onto the edges of the appropriate holes on DAC, do I simply cut the micro-connector off the end of the normal USB charging lead the comes with the battery back and strip the wires? Also, if I do this, how do I know which wire is grnd and which is 5v? Is the stripped USB cable likely to be black and red inside?


Again, my apologies for any newbie ignorance!





Many thanks,



ANDREW

[PeteB]

Hi Andrew, and welcome to RuneAudio!

First, you should use headers and jumpers if possible. There are good reasons why those were invented! Since I know you probably do not want to do that (chuckle)... :

1) To do it right, you should put a wire, a 2-pin header, or some other kind of lead THROUGH the holes at P3, and then solder it so the solder wicks up into the hole, and forms a solid connection. If you see a hole, it means something is supposed to go through it.

2) Yes, IF you remove the resistor. That is the link between the two power supply rails. (R14 is actually a zero-ohm jumper in the form of a resistor, so it can be assembled and soldered by machine in the factory)

3) It will relieve the power supply, so indirectly it may improve the sound, but probably not if all is working now.

4) Depends on the cable. You might need a thicker (higher awg*) cable, like the 20 awg cables advertised on amazon.com, from Anker for example. In either case, you should use a meter to check, but normally the shield is the return (ground), and the thicker 20 awg wire, usually red insulation, is 5V. I posted a pic here:



Best of luck,

Pete

* edit: this should read "lower" awg (preferrably 22 or 20 awg)

[Fenric77]

Hi Pete,

Many thanks for your help and advice.

Can I ask another questions, if that's ok?

It's just on how to go about most effectively attaching a power supply to headers on the 5v and GRND sockets, as you suggest.

Can you advise what socket / header I need to solder to the DAC to most effectively attach a power supply? I would prefer not to solder the wires directly, so I can still unplug the PI from all power easily, so a female micro usb socket would be ideal as then I could plug and unplug my power supply with straining the joints, but I'm at a loss for how to achieve this., This would also mean I could use a standard micro to usb cable from my power pack without wiring on another connector.

My problem is tracking down an appropriate header to be able to do this. All USB headers seem to be 4pin, with this power and ground on the outside pins. The 5v and GRND holes on the DAC are too close together to be able to use these headers.

I see there are high-cost linear power supplies for the DAC available online, and they appear to have hard-drive to motherboard style power connectors on them, but how would they connect to the DAC?

If soldering a female micro USB socket is not possible, is there an appropriate 2pin header that I can I solder to the DAC, which will allow me to easily affix an unpluggable power cable (after I attach an appropriate connect to the power cable's stripped red and black wires)?

I'm sorry to be so vague, I'm just not finding anything appropriate on Amazon, Ebay or online parts suppliers. I realise I can trip a bigger header down to 2 pinks, but that just gives me two pole to attach normal jumper cables to, and I'm looking for something with a proper disconnectable connector (ideally micro USB, but a power connector would be fine).

Many thanks in advance!

ANDREW

[hondagx35]

[Fenric77]

Many thanks, Frank, the connectors look perfect!

My only worry, if that I have 20awg Anker usb cable (standard male USB on one end to connect to the battery pack and micro male usb on the other to attach to the DAC - or to strip and connect / solder to wires connected to the DAC).

I'd prefer not to have to solder the thin wires such as those in your link on to the end of the thicker wire, which would then go through two connectors before attaching to the DAC.

Is it possible to mount the female connector directly onto the DAC, and to attach the male connector directly onto the stripped red/black ends of my Anker USB cable after I cut off the male micro usb socket?

I'm led to believe that using the single 20awg cable will make for a 'cleaner' power supply to the DAC's analogue circuits, and hence better sound (which is of course the point of using a separate PSU). I don't want to reduce the effect of this by using standard thin cable soldered to my 20awg cable.

What are your thoughts? Am I being paranoid, or is there a solution I can find with just connectors that can be soldered to the DAC (female) and attached to my Anker lead (male)?

As ever, many thanks for your interest and assistance!

ANDREW

[hondagx35]

Hi Andrew,

with a bit searching you will also find them in 20AWG or thicker.
And yes they are also available as pinheader for circuit boards.
Search google for
2 pole pin header
You have to find the right size 2mm or 2.54mm

Frank

[PeteB]