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  1. #1
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    YAP: Yet Another Player

    Hi All,

    so some lifestyle changes resulted in listening a bit more through a pair of cans and to that I dusted off my (vintage?) AKG K-500 that I still like. The spare SB3 that I kept in a drawer doesn't have the oempf to drive these headphones properly. So something was needed and through fellow DIY'ers I was pointed towards to TI's TPA6120A2 headphone amplifier chip. I could have build a standalone amplifier that takes the signal from the SB3 but that would result in a less practical solution (2 boxes, cables, ...) to move around in the house. A single box solution is preferred and now that winter is upon us and we have long evenings it is perfect time for a DIY project (instead of being a coach potato). There are many other headphone amps designs out there but I liked the simplicity of using the TPA. Although 'simplicity': the TPA needs some thoughtful PCB design to prevent stability issues.

    So far I got myself a Pi Zero 2W and a DAC from Hifiberry. To my surprise the headphone amp on that DAC board drives my AKG a bit better, but still need to crank up the volume quite a bit. So I guess I still am on for an amp with some more gain.

    The player will not be outfitted with a screen or IR receiver (at least for now) but will get some buttons. Most of time I use a tablet/phone to control LMS. But it is good to have a few buttons like play/pauze/mute/volume. The internals should be a tidy as possible, I dislike multiple boards tied together with a cable loom. Parts, case, schematic, look and feel. It goes all hand in hand and influence each other so I made already some possible Cases, PCB layout concepts.

    The case will likely be something like this (this one is about 25cm/10" wide) but will not be the final version.

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    Obviously working on a schematic too.

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    And gettig some idea about the pcb (although this is already out-dated....)

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    As you see I'll not stack the DAC on the Zero, I don't want the DAC to cover the antenna area, it probably will not be a real issue (I have it stacked at the moment too without issues) but I also want the whole PCB to have a low profile.

    Software to be used: PiCorePlayer, SqueezeLite (duh), SqueezeButtonPi.

    So far for now.
    Last edited by hsmeets; 2021-12-11 at 03:01.
    does the all-black SB sound better than the white SB?

  2. #2
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    Name:  A35F0AE6-494B-4FAF-AEE8-3F74C06D1BAF.jpg
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    Seriously considering touch controls. Not a tft display but sensors behind a sheet of PMMA.
    Last edited by hsmeets; 2021-12-17 at 11:59.
    does the all-black SB sound better than the white SB?

  3. #3
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    Some progress. 3 out of 5 schematics and PCB's.

    Carrier board for RPI + DAC, with some GPIO's available on the righthand side connector (uController/Frontpanel)
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    PSU: 1 small SMPS for uController, 1 larger for RPI and DAC and 1 linear -12 and +12 for the head-amp.
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    Amplifier: 4 layer board, using the TPA6120 and an OPA2134 as input buffer (composite) to keep the DC offset from the TPA6120 in check.
    Name:  Schermafbeelding 2022-01-03 om 22.09.57.jpg
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    does the all-black SB sound better than the white SB?

  4. #4
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    Quote Originally Posted by hsmeets View Post
    Some progress. 3 out of 5 schematics and PCB's.

    Amplifier: 4 layer board, using the TPA6120 and an OPA2134 as input buffer (composite) to keep the DC offset from the TPA6120 in check.
    Name:  Schermafbeelding 2022-01-03 om 22.09.57.jpg
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    Nice idea and nice 3D pictures.
    What kind of program are you using ?

    Where is it possible to manage HW switches to control functions ? I'm very interested!

    Thanks
    Last edited by PaulH; 2022-01-12 at 12:24.

  5. #5
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    Quote Originally Posted by PaulH View Post
    Nice idea and nice 3D pictures.
    What kind of program are you using ?

    Where is it possible to manage HW switches to control functions ? I'm very interested!

    Thanks
    Software for schematics and PCB design is KiCad (Version 6). It also does the rendering.

    PCP/LMS control via HW switches connected to GPIO was tested succesfully using the SqueezePiButton extension.

    Specifically I will use touchsensors using the AT42QT1010. For testing porpose I used the Adafruit touchsensor using the same chip.

    Regards,

    Huib
    does the all-black SB sound better than the white SB?

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