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Electronics RaspberryPi Amp Box - UPDATE - up and running!

Discussion in 'Modding' started by talladega, 14 Feb 2013.

  1. talladega

    talladega I'm Squidward

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    So I got myself a raspberry pi last year not knowing what I was going to do with it at the time. After a while I decided I wanted to build a music player for our bedroom so once I had the time I got the Pi hooked up and installed SqueezePlug and SqueezeLite on it (http://www.squeezeplug.de/). I installed Logitech Media Server on my WHS 2011 box, connected my Pi to a little amp and was able to stream all our music through the Pi.

    So my goal in the end is to have one box that has/can do the following

    1. Hold the RaspberryPi, Amp, DAC, and Power Supply
    2. Connect to my network wirelessly to stream music from my server and internet radio
    3. Be able to control it with a laptop or smartphone/tablet
    4. Have multiple inputs on the amp to switch between the Pi, a front 3.5mm input, and an RCA Stereo input on the rear.
    5. Line out (if possible) so I can connect this to another amp if I felt like it.
    6. Power Supply all internal for the Amp/DAC/Pi/USB Hub so I can have one plain PC power cord to plug in



    Here is the hardware I was thinking of using


    Startech USB Hub
    USB DAC
    TA 2020 Amp - These seem to be liked over at DiyAudio
    12V Power Supply
    12V to 5V Converter
    Speaker Posts
    RCA Input/Outputs
    2x Power Switches for the amp and raspberry pi
    AC Power Socket with Switch
    Input Selector Rotary Switch


    Here is a very pathetic mspaint drawing of what I want to do.
    [​IMG]


    I will desolder the power input from the amp board and solder wires to it from the 12v power supply with a switch inbetween that connection so I can turn on or off the amp by itself.
    I will also remove the rca connections on the amp board and solder wires from the input switch to the amp.

    The 5v power to the usb hub and raspberry pi will also have a power switch so I can turn those on and off by themselves as well. (incase I need to reboot the raspberry pi)


    Now I am pretty sure this should all function the way I'm wanting it to. However, is this the best and cheapest way to do it? Is there going to be noise problems with all these devices in one box? Is there something that I will need to do a certain way to make this work?
    It's a lot of money to spend so I need to make sure I cover all my bases here and do it right.

    Any input would be very helpful :rock:
     
    Last edited: 20 Apr 2013
  2. jrs77

    jrs77 Modder

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    Shielding, shielding, shielding! That's the most necessary and cruicial part of such a box, especially the PSU and the amp needs to be shielded, as they tend to interfere with each other and the WiFi.

    Or you could buy a nice nuForce Icon 2 and make a box for the Pi that looks exactly the same.

    I've recently purchased a Scythe Kamabay Amp and it's a very good amp for the money. You could use that and integrate it into a case for the Pi. This would do away with the PSU and the shielding-problems.
     
    Last edited: 14 Feb 2013
  3. talladega

    talladega I'm Squidward

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    How and what do I use for shielding?
    And does my plan even look realistic/possible?
     
  4. coolamasta

    coolamasta Folding@Home CC Captain 2010/11/12

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    Nice little project there, will be watching with interest :)
     
  5. jrs77

    jrs77 Modder

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    Looks quiet possible to me.

    For the shielding you need metalcages, like a faraday cage. Simply read up on electromagnetic shielding and go from there.
    Make sure that the amp, DAC and PI are shielded against the electromagnetic field of the PSU. The amp also needs shielding against the WiFi.

    Basically you simply build faraday cages around the Pi, the DAC and the amp. And make sure that everything is properly grounded.

    EDIT: The mini-amps like the TA2020 one you linked above, or the ones I linked usually have external powerbricks, which makes additional shielding against other components unnecessary, as the enclosure works as shielding allready.
     
    Last edited: 14 Feb 2013
  6. talladega

    talladega I'm Squidward

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    So you're saying that if I use an external power brick for the amp instead of that internal one I linked to, I don't have to worry about EMI?

    If thats the case, then can I take the 12V power from that power brick and also run it into that 12v to 5v step down to power the Pi and USB Hub?
    So basically the design would look the exact same except the 12V power supply would be external.
     
  7. jrs77

    jrs77 Modder

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    You still need to shield the amp from the WiFi, if you use a USB-Dongle without external antenna ;)
     
  8. talladega

    talladega I'm Squidward

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    Is there a way I can test that to see if it will be needed or not? I have a little Lepai TA2020 Amp sitting out outside of its casing. I guess I could power on the raspberry pi right next to it and see if it does anything?

    What would happen from interference? Background noise in the speakers?


    I wonder if all of these problems would be eliminated if I made one case for the Pi/usb hub/dac , and one case for the amp/input selector? I would still need external Power Supplies for each to not have any interference, right?
     
  9. jrs77

    jrs77 Modder

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    Yeah, white noise is usually to be heard, when components are not shielded good enough. Bad/cheap powersupplies have the same effect.

    White noise is aswell a problem with some onboard audio-chips, but a USB-DAC cancelles that problem.
     
  10. talladega

    talladega I'm Squidward

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    Oh I see. So the only thing that would be affected here is the amp because the Pi uses a DAC?

    I guess then if running the Pi next to the amp give no noise, then I can have all devices in one box and just use external power? Then I'll build a fancy enclosure for the PSU! :)
     
  11. jrs77

    jrs77 Modder

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    I played a bit in SketchUp after aquiring the measurements of all the parts...

    [​IMG]

    Three enclosures of the same footprint, stackable atop of each other. The box for the AMP/DAC can be a little bit less high tho.
    Footprint would be 150x90mm and the both bigger ones would be 50mm high and the AMP/DAC could be only 30mm.

    There would be enough room in the AMP/DAC box for the input-selector and all the jacks and knobs.
     
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  12. talladega

    talladega I'm Squidward

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    you are a mind reader. lol
    that was exactly my plan when I first started thinking about doing this!

    So with this I could have a regular PC power cord going to the PSU box, then a short power cord going from the PSU box to the Pi box, and another to the AMP.

    This would be nice as I could use them as individual piece if I chose to.

    Do you think wifi signal would be strong enough using one internally, or would an external antenna be needed?
     
  13. alpaca

    alpaca llama eats dremel

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    Depends on if you will 'faraday cage' it (is that a verb? to faraday cage? to cage faraday?:lol:) If it's a non-conductive material, your range would be a bit diminished, but not gone if the signal is strong enough, if it is, your range would be gone, and you'd need an external antenna.
     
  14. jrs77

    jrs77 Modder

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    Just place an USB-jack in the case, so that you can plug the WiFi-dongle in from the outside. Would be a good idea anyways to have the USB-plugs on the outside of the case, for easier access.
     
  15. talladega

    talladega I'm Squidward

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    Yeah, that would probably be best.
    Now can I make these cases out of wood or do they have to be metal to prevent EMI?
    Reason I ask is the cheapest no crap boxes I can find will be $50 for 3. Thats alot just for a box.
     
  16. jrs77

    jrs77 Modder

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    Seeing that the PSU you linked is basically shielded allready by it's own housing, additional shielding is probably not needed, but you could use some thin sheet of copper and make a very basic shielding.
    However, you might still want to think about building the boxes out of metal, just to make the boxes nicer and more "professional" looking. There's a company for that and they even have their own free software for you to model the thingy -> http://www.protocase.com/

    You can get an instant quote for the pricing there aswell -> http://www.protocase.com/price/instant_quote_ushape.php. A U-shaped satin black painted box from 0.06" 16 gauge metal shouldn't be that expensive.
     
    Last edited: 15 Feb 2013
  17. GuilleAcoustic

    GuilleAcoustic Ook ? Ook !

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    MuMetal all the way :D. A 1:1 isolation transformer between the PSU and the amplifier board could be nice to avoid ground loop.
     
    Last edited: 15 Feb 2013
  18. jrs77

    jrs77 Modder

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    Yeah, sure, if you have sources for MuMetal around the corner :p
     
  19. GuilleAcoustic

    GuilleAcoustic Ook ? Ook !

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  20. jrs77

    jrs77 Modder

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    Ah, OK.

    Anyways. I made a fast sketch of how to build a very nice looking box. All you need is some 1mm aluminum and then something like 3-5mm acryl.

    [​IMG]

    Easy to build, and very good looking. All the holes needed are very easy to drill in 1mm aluminum aswell.

    If you know someone, who can cut and bend the aluminum for you it's even easier to do, allthough 1mm aluminum is easy to bend even without a bending break.
     
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