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transport audio through Wifi instead of USB OTG to USB DAC

  1. autur
    The problem: I hate cables and the thought of plugging back and forth my smartphone from its charger to the USB OTG cable connected to a DAC is off-putting. My ideal setup would include smartphone --> (wireless) --> wifi device (instead of USB OTG) --> usb DAC. Question: are there any wifi devices that can transport data from a smartphone to a usb DAC in a pass-through manner without decoding the files? Like this one on Indigogo that failed to get support.

    I know that that there are small wifi DACs like the Chromecast Audio that can stream from your smartphone, but from what I understand it cannot purely transport audio to external DAC, and it supports only 24/96khz.
    Last edited: Feb 25, 2018
  2. ProtegeManiac Contributor
    If you just want to maintain the interface of the smartphone why not just run a Headless Audio Server? Take a miniPC, particularly an Android MiniPC or some Intel NUCs that way you can run mostly fanless (ie no more noise than the smartphone), and after initial setup the smartphone will serve as both screen and remote. If you prefer certain apps for playing music or running EQ/Crossfeed, you can run Android apps on the Android miniPC like a Raspberry Pi or any prebuilt as long as it runs Android. It won't be any larger than your DAC (probably smaller even), so you can set it near the DAC and connect to it via USB. You can access any NAS on your network via LAN as long as the player app supports it.

    A slightly easier set up would be to use a music server, but: 1) these can be expensive and 2) not all of them run all streaming services (newer ones at best run Spotify).
  3. autur
    Music servers / SBCs are ideal for people who have large storage needs (need to fit their music on 1+TB hard drives) and dont mind the extra space and energy consumption. Since I'm using Tidal/Spotify and dont need more than a microsd card, I want a small efficient setup involving no more than smartphone and a pile of Schiit for cans like the HD 650 :)

    Would you not agree that there is a market for the kind of wifi device I'm talking about? I don't quite understand why it doesn't already exist.
  4. ProtegeManiac Contributor
    Because your phone has to deal with its own power consumption isses, ie, a battery, and an Android miniPC using a comparable mobile device processor won't necessarily consume more power on top of not having to charge a battery and hence doesn't add to chemical waste? HDDs need power too, but you don't necessarily have to run a mass storage NAS. You can put one portable HDD into a USB port on a Minix Neo. Or just put an SD card into the miniPC - some have them built in.

    Second, smartphones were optimized more for the easier connection with BT, so you can more easily find BT receivers with hi-fi equipment 2v line output than DACs with WiFi for direct streaming from a phone. Basically, on top of the DAC itself, they'd have to write up the software to get this to work, which they already do...on music servers. By their market study they might as well ptu the WiFi on that and get more sales to people who need them for accessing massive storage solutions.
  5. autur
    I hear you on all your points, but there is already a significant market of people who use USB OTG from their smartphone to a DAC who I'm sure would love to free themselves of another pesky usb cable. And we already have wifi DACs like the Chromecast audio, so the technology is already available for a rather simple wireless audio bridge that could cost even less than the Chromecast. In short, I think there is potential demand and no tech barriers, but then again the device I'm describing may already exist, which is why I put forth the question.
  6. onevstheworld
    Doesn't @ProtegeManiac Raspberry Pi suggestion tick all those boxes? It runs off a phone charger, so power consumption shouldn't be an issue. And even with a case, it's less than half the size of your stack's Modi.

    AFAIK the CCA does send a digital signal directly to a DAC via optical. Also is the max resolution even a limitation if using Tidal? Doesn't Tidal max out at 24bit 96khz?
  7. ProtegeManiac Contributor
    Yes, and that includes me.

    However "significant" does not always translate to "significant enough to make manufacturing sense." You don't even have to get to WiFi input on DACs for that - look at how many desktop units aren't even tested by manufacturers (let alone designed from the ground up) to work with USB OTG. You'd think the "significant number of people using USB OTG" would have motivated that, but no, it hasn't, which is also why we're not yet at the "helping people free themselves of another pesky usb cable" part.

    Don't mistake the mass market to just translate to the Hi-Fi market like that. Apple had the Airport, so they had the tech to stream from HDDs, but people still went for iPod docks that convert them into digital transports, even for people on pure 2ch (ie no surround, no TVs) that have to get up to switch albums/playlists since they can't see the screen. That was still a step forward from the 256kbps max res that the Airport can handle, assuming the iPods were fllled with ALAC.

    Similar problem with the Chromecast. Even if it can handle 16/44.1, hifi manufacturers are looking at 24/96 as the future (ie digital albums nowadays are shifting to digital download sales as either 320kbps 16/44.1 or 24/96 FLAC) along with DSD, plus there's an ongoing trend of vinyl resurgence, so chances are they're still trying to figure out how to get that much bandwidth to run FLAC beyond 16/44.1 apart from music servers that basically just trade a CD transport for a LAN cable and a NAS (or just an HDD on USB), which, given the file size, is naturally what developed first. If you want to look at demand, that's where they projected it would be, given file size, ie, a bank of HDDs in another room would have a huge advantage in storage over microSDs in smartphones (which not all phones have to begin with) without the mechanical and cooling noise penalty.

    By contrast it's easy enough to get the Chromecast out there given the use people will have for them - running Spotify on a living room HT system they got cheap in some big store. You'd have to wait for manufacturers to see that Tidal is as much of a thing as people downloading albums (which again are now being sold at 24/96) or ripping their own CDs to put WiFi input on DACs. There are music servers that run as DACs of course but again, the way they're structured, the phone is the interface, and they directly access Spotify (just like MiniPCs or HT receivers) and the phone is relegated to an interface device for those who don't have this kind of device in an HT system (for the screen).

    You can always either just use a Raspberry Pi with an external HDD, or just replace your DAC with a BT receiver so you can still use the phone as a wireless server.
  8. kkl10
    If your smartphone features bluetooth, then you want a bluetooth receiver. The market is getting flooded by bluetooth devices that do exactly what you want.
  9. autur
    To the last three repliers, I appreciate your thoughts and suggestions. CCA indeed sends a digital signal directly to a DAC via optical and supports max 24-bit/96khz, but from what I've read, this is not in a purely passive manner (I'm not so savvy about the technical details, so please correct me if you know better). For example, what happens if you're streaming local-stored files that are 24/192?

    Regarding the BT suggestions, as you all probably know BT is not a solution for lossless playback and even the newer aptX standard uses a lossy codec. It's obviously not bad, but it's a step below USB OTG. I'm talking wireless transfer of the same data that would be transferred through USB. And I agree or am aware that this can be avoided by just having Raspberry Pi or some other SBC do all the streaming/playing, while your smartphone acts as a remote control. I suppose that's what most people who want remote access do.
    Last edited: Feb 26, 2018
  10. ProtegeManiac Contributor
    It's downsampled to 24/96. You only need to worry about it if the resampling is done on the fly, which you can circumvent by keeping 24/192 in archive and use a program to resample them to 24/96 for what you'll use to listen with. Otherwise, 24/192 isn't really any advantage over 96khz or 88khz anyway.

    It's being suggested to be used for Spotify if your main concern is convenience more than not messing with the signal in ways that will degrade the source material. If it's more important that you can charge then do that. I dock my phone when I get home to charge on the dock the nswitch it out for the OTG cable when I'm ready to listen, ie, I've cooked, eaten, showered, fed the cat. Also by that point the tube will already be past its warm up phase (during which time I have a cheap tablet running Spotify to BT speakers in the kitchen, because as much as I prefer the sound of my IEMs, they're a bad idea when cooking or around cats, not to mention chewing with those in your ears will make every chewing sound louder than the music).
  11. onevstheworld
    Last edited: Feb 27, 2018
  12. autur
    I think I came across that article in the past. From the Conclusion: "My testing revealed that the device can be picky when it comes to supported file formats. Some FLACs play perfect while others don't. I'm certainly not going to convert my entire 60,000 track library to a specific level of FLAC compression with a specific encoding application in order to play the files on the Chromecast Audio, but people who libraries are already in the supported format should be happy."

    CCA is fine for many people, but for those who want bit perfect music at highest resolutions with no downsampling, it's not there yet. (I'm not one of them; just making an observation).
    Last edited: Feb 28, 2018
  13. labrat
    Chord MoJo with the Poly module attached can receive WiFi (though at a price for this small setup!) !
    Most smartphones can act as a WiFi hotspot.
    But I cannot see if any smartphone can transmit music directly to the WiFi .
    Maybe a tablet?
    So if you can make an app for your smartphone to do this, you have your solution!

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