Building a USB-C DAC in as small a package as possible

Submitted ⁨⁨1⁩ ⁨day⁩ ago⁩ by ⁨northernscrub@lemmy.world⁩ to ⁨askelectronics@discuss.tchncs.de⁩

Given the endless problems with attempting to properly initialise ALSA with the qualcomm chipset in my device, I’ve resorted to the idea that I’ll be designing a larger case, with a larger screen (and hopefully no shitty curvy corners) and an integrated DAC with probably a small headphone amplifier.

Ideally, I would like this to be addressable, and have the facility to run an equaliser on-board that can be configured via the USB connection, although I’ll settle for bluetooth if the former is too complicated. It will also need to fit inside the phone housing (which will likely be around 9-10mm). I plan on an aluminium frame, so heatsink facilities should be easily manageable. The USB connection will, of course, need to be a passthrough connection to facilitate charging the phone - having a separate USB-C socket on the board is fine, I can probably adjust for this.

Am I setting my aspirations too high, or are there components available that meet these specifications?

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roofuskit@lemmy.world ⁨1⁩ ⁨day⁩ ago
The USBC to 1/8 adapters for phones, particularly the iPhone have an integrated DAC.

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- northernscrub@lemmy.world ⁨1⁩ ⁨day⁩ ago
  I’ve looked at these, but they lack the integrated amplifier (afaik) and the configurable equaliser. Those are two super important features that pretty much break the idea for me.
  
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- PagPag@lemmy.world ⁨1⁩ ⁨day⁩ ago
  First thing I thought of too.
  
  Sorry OP, you’re not building anything smaller than this cheap item from apple.
  
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  - northernscrub@lemmy.world ⁨12⁩ ⁨hours⁩ ago
    After a night’s thought, this might be an interesting idea. Although I’d need to figure out how to add a programmable interface to it.
    
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quiescentcurrent@discuss.tchncs.de ⁨1⁩ ⁨day⁩ ago
It somehow feels like you put a lot of thought into this already and missed starting from the beginning in this post.

What device do you want to have a USB-C DAC for? What’s the actual size limitations and what power do you want to draw that would need a heatsink? Do you have specs in mind, or is there a comparable project already available to look at?

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- northernscrub@lemmy.world ⁨1⁩ ⁨day⁩ ago
  I’ve put some thought into it, but realistically I lack the experience to flesh out the idea.
  
  I’ve seen a few small DAC concepts out there, like www.elektroda.com/rtvforum/topic4091483.html or that iPhone modification that Strange Parts did a few years ago, but none of these really 100% match my needs. As for the sizing, the only real answer I have for you is “small” - whilst it is intended for integration into a phone, I’m going to be building a housing for that phone from scratch, so the size requirements are somewhat led by the dac itself. I had a few ideas about using a flexi-strip in place of a solid PCB too, but I think that’s aiming too high for my non-existent skillset. Instead, I have no problem redesigning the board to be long and thin if necessary, or squat and fat in the alternate. Realistically, it’s probably going to be somewhat L-shaped, but there’s a good two inches or more of width and something like six inches of height to work with - minus the PCB of the phone, that is.
  
  The actual handset it will be accompanying is a Sony Xperia 1 IV, but that’s largely meaningless as we can add pretty much any additional size to it up to a reasonably large handset within the last ten years (preferably with an OLED display, but I’ll be somewhat limited in terms of compatibility anyway and might have to end up running the screen in an alternate fashion somehow, I haven’t thought too hard about that side of things because the project is useless if I can’t design a DAC inthe first place).
  
  The heatsink stuff was really just a suggestion, I’m not actually sure if it will be necessary, but it’s good to have the option.
  
  Specifications wise, it essentially needs to do four things:
  
  Pass any connected headset microphone through to the handset
  
  Run an EQ that is addressable and configurable from the handset
  
  Have a volume ceiling at least comparable to a fifth-gen iPod video (i.e. a wolfson chip)
  
  Take power from, and pass data and power through to, the existing USB-C socket on the handset.
  
  The bit that I’m stuck on, really, is the addressable EQ. I could possibly go with some sort of Arduino-esque solution, but that’s a lot of lifting for a single-purpose device. I have no idea where else to start looking - I know there are RISC chips out there that run on nothing but a button cell, but again I’m clueless as to whether or not this is a good idea.
  
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  - quiescentcurrent@discuss.tchncs.de ⁨1⁩ ⁨day⁩ ago
    Thanks for the detailed answer, that helps a lot for my understanding.
    
    The project sounds like a lot of work, especially for such a niche application. Do you have a crowd to support this (with time or money) or do you plan pay for this and sell it in the end?
    
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