What about this DAC? Should the Onkyo app work properly, bypassing the iDevice dac?
Which DAC? I have an Onkyo AVR using a wi-fi adapter (a Netgear computer adapter w/ the same wi-fi chipset; the official Onkyo adapter gets terrible signal in my house due to location). So I do use the Onkyo app but not much and only as a remote control. Do Onkyo AVRs stream audio from the AVR inputs, or the "Net" features like Spotify, via wi-fi or bluetooth to the iOS and/or Android apps for listening? Wi-Fi and Bluetooth are both digital wireless standards. So what's coming from the Onkyo even if it's sourced digital, been processed to analog via the Onkyo AVR's DAC, it's going to a device app it's going digital. It's going as data. Which means something has to convert that digital data to analog audio information. On iOS devices, if it goes out the headphone jack, or out the Lightning connector via an Apple or 3rd-party adapter Lightning to line-out, it's going through a a DAC. Either the iOS devices DAC or the adapter's DAC. You can do a DAC in software. It's not very efficient on this scale, but you can do it. So the Onkyo app could have a software DAC that processes data from Onkyo AVRs, but really there's no way to bypass the digital path through a DAC related to the device. Android devices, I don't know, but I doubt it, not unless they're substantially hacked. And there's no reason to do it with popular Android devices because they support USB DAC+amp devices via their connector ports, even if an adapter is required to take a USB cable. Android device makers don't so often care if you drain the battery a lot faster than the device is rated. They warn you via a message on the device or in the manual and then let you connect about whatever will work via USB. Apple won't let you do that. You can't connect a USB device that reports in its profile, or is detected to, draw much power. The Apple USB adapter draws a little power, the SD card reader draws a little power, that's okay. A DAC+amp has at least the potential to draw a lot of power and if it accurately reports in its profile what it can draw, the iOS device isn't going to allow it to handshake up with the iOS device. You can plug it in but you can't use it and the iOS device will neither recognize it in the UI or provide it power.
The whole business of bypassing DACs on mobile devices is kind of a mess. A lot of people think they're using their alternative DAC+amp's DAC when they are not. They may have analog line-out but it's still going through either the device DAC or the adapter DAC. The only way I've seen to truly bypass the device DAC and the adapter DAC, if there is a DAC in that particular adapter, is a trick of putting a hub between the alternative DAC and the iOS device. Usually a powered hub but some unpowered hubs will work. It's whatever the hubs report as max power draw, is actually drawing, that's the thing the iOS device uses to decide. If the hub plays nice, you can connect a DAC+amp, and select it as the audio output device in iOS in the menu you where you'd normally select the usual audio output options (headphones -- DAC is iOS DAC, Airport Express for Airplay -- DAC is Airport Express DAC, Apple TV for Airplay -- DAC is Apple TV DAC). If the external USB DAC shows up there, you can bypass the onboard DACs. But this only works with 30-pin dock-connector iPads. iPhones always choke on the power draw. Lightning iPads using the Apple USB adapter choke on the power, using the Lightning-to-30-pin adapter with the old 30-pin dock connector line-out adapter, the Lightning-to-30-pin adapter has its own DAC and there is no way around that DAC. Besides which, you're connecting analog line-out, not USB digital, so there's no digital for the DAC in the external device to convert to analog.
There's a Wildlife Control song that makes a bit of fun of this whole analog vs. digital argument. The song says it really doesn't matter. The song is pretty much right. Ever since there was so-called audiophile equipment there have been components and cable wars, way before any content signal had to be converted from digital data to analog audio. Back when compact disc first came out it was part of the standard that a properly licensed product for the format be labeled with a code that indicated how it was produced. The Holy Grail was DDD. Digitally recorded, digitally produced, digitally mastered. It didn't exist. Studios didn't have digital equipment so everything was AAD. After a while some things were ADD. These day pretty much everything is DDD but nobody buys CDs anymore and they dropped the code requirement for CDs anyway. Probably because pretty much everything was DDD, or ADD, and possibly because the analog-is-better crowd had garnered enough public attention the Compact Disc consortium didn't want you to know you were buying a DDD recording.
It's well known Jack White was an analog-only nut for a long time. Apparently one day he woke up and realized he was putting himself and a bunch of production people to ridiculous pains as 99.99% of his product was going to be somewhere down the line processed digitally. So he quit bothering. Is pure analog better? I don't know. It often sounds different to some people, and it's a fact there's no such thing as an uncompressed digital recording. All digital formats are to some degree lossy. Lossless is a marketing word. You lose audio wave information when you convert it to to binary data. It's compressed by its nature and it's unavoidable. Lossless just means much less compressed. But is analog actually better? Well, for starters, good luck finding a way to listen to analog audio. Playing a vinyl LP through a modern amp is not an analog experience. I have a FiiO E12 Mont Blanc portable amp I like quite a bit. They call it analog. It's not analog. It's all analog-in and all analog-out but it's an amp-on-a-chip so whatever comes in through the analog input is getting digitally processed somewhere. Same for the overwhelming majority of modern AVRs and ARs. They're amp-on-chip designs. Everything is digitally processed at some point.
Vinyl and other older analog sourced technologies sound different, certainly. And I could show you a purely source analog signal on a signal analyzer compared with a digital-to-analog signal and I could point out how much is missing from the source digital signal. But it's not anything human ears can hear.
People come at this from the wrong side. They'll drop $500 on a tabletop headphone DAC+amp down and plug their laptops into them and listen to the output audio with $300 Beats or some similar sort of headphone. If they put a lot less money into just a decent pair of headphones, those headphones will make their sorry laptop amp and DAC shine. You can spend $3,500 on one of these fairly new Sennheiser tabletop DACs and Sennheiser headphones and it'll sound great off your computer but a week later you won't know the difference. $400 Sennheiser headphones alone would have been more than enough to give you the audience experience you want. I have a pair of Sennhesier HD201s. Thirty bucks. They're weak all over and I'm not a fan of mega-bass, but there's like no bass out of the HD201s. Pair them with a $150 desktop or portable amp-on-chip unit with a bass boost feature, they sound like premium headphones.
Anyway, start with the headphones. Then for a computer throw in a reasonably priced external DAC+amp. For portable devices, don't sweat the DAC and everything you'll to go through to use an external DAC. Portables devices, listening conditions are rarely ideal, anyway. A 5mph breeze will throw the whole deal. Good, durable headphones and if you want a little boost then an economical portable amp, that's plenty.
Sorry this is so long but a lot of people come to these forums less for technical help or general buying advice and more to find out how to spend a bunch of money to "get it right." There is no "right." The only "right" is what sounds right to you. And that will vary based upon what you're listening to. Jinkies, it will vary based on your mood. Putting together so-called audiophile systems is a hobby, like building Lego sets. If you know it's a hobby, it's how you choose to spend your time and money, and you realize you'll always be messing with this stuff, with connections, with new components, then you'll be fine. Trying to "get it right," you'll drive yourself crazy.
This "I can hear the air between the string" stuff is nonsense. I've been in production studios, symphony recordings you can hear one musician barely, just ever so slightly, bump her music stand with her knee and it rocks on its based for a few seconds. Wonderful. If you're an FBI audio analyst. But why would I want to hear that on a recording I'm playing to enjoy?
Like the song says, it really doesn't matter if it's analog or digital.
