Understanding iPhones/iPods - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th December 2014, 08:14 PM   #1
diyAudio Member
 
Join Date: Dec 2014
Default Understanding iPhones/iPods

When an iPhone/iPod is connected to a compatible receiver via USB, how does it send audio through?

On older iPods sporting the 30-pin connector, there are line out connections on the connector, but these aren't connected to the USB end of the cable. This would imply that audio signals are sent digitally.

Here's where I get confused:

- audio receivers would typically expect a mass storage device when a USB connection is established, meaning it looks for audio files. In that case, how do streaming services such as Spotify work?

- since iPods do not act as storage devices, does this imply that all audio is streamed digitally?



I really hope someone can help clarify this for me.


Thanks!!
  Reply With Quote
Old 6th December 2014, 11:35 PM   #2
diyAudio Member
 
Join Date: Mar 2002
Location: Glasgow
Many Apple devices actually support USB audio. It used to be possible to plug a USB DAC into the IPhone/iPad camera connection kit. So, the receiver probably just looks like a USB soundcard to the iDevice.
__________________
"Some of the arguments conjure images of white-coated engineers with putty in their ears, designing audio equipment and not caring how it sounds, only how it measures. I have never met such a person"http://scopeboy.com/amps
  Reply With Quote
Old 7th December 2014, 12:07 AM   #3
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
There are two ways USB audio works.
1/ Device acts like flash drive to hold audio files.
2/ Device converts immediately digital data to analogue data.

I have a MP3 player that does (1).
I have a NDX900 USB player that does (2).

Last edited by nigelwright7557; 7th December 2014 at 12:10 AM.
  Reply With Quote
Old 7th December 2014, 01:18 AM   #4
diyAudio Member
 
Join Date: Dec 2014
Thanks for the replies.

I can see how the iPod would see the receiver as some soundcard, but how does the receiver distinguish an iPod from a flashdrive?
  Reply With Quote
Old 7th December 2014, 02:22 AM   #5
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
In Apples developer infothey may have the specifics. If it is out via USB it will be as if you were using a computer to feed your DAC via USB.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 7th December 2014, 11:03 AM   #6
diyAudio Member
 
Join Date: Mar 2002
Location: Glasgow
Quote:
Originally Posted by cukaracha View Post
Thanks for the replies.

I can see how the iPod would see the receiver as some soundcard, but how does the receiver distinguish an iPod from a flashdrive?
It is not even the same way round. The phone is the USB host, the receiver is the USB device.

Most phones have "USB On The Go" which can work either way round depending on the status of a selector pin. My Android phone appears as a USB device to my computer, but using an OTG adaptor lead I can plug a flash drive or USB audio DAC into the phone.

Apple probably have USB OTG too, just hidden in a proprietary connector and augmented with a secret chip that makes it only talk to Apple approved devices.

If the receiver can accept a flash drive and an iPod in the same USB port, and transfer audio digitally, then it must have some sort of OTG functionality too.
__________________
"Some of the arguments conjure images of white-coated engineers with putty in their ears, designing audio equipment and not caring how it sounds, only how it measures. I have never met such a person"http://scopeboy.com/amps
  Reply With Quote
Old 7th December 2014, 04:50 PM   #7
diyAudio Member
 
Join Date: Dec 2014
Thanks again for all the replies.


Quote:
Originally Posted by scopeboy View Post
My Android phone appears as a USB device to my computer, but using an OTG adaptor lead I can plug a flash drive or USB audio DAC into the phone.

If the receiver can accept a flash drive and an iPod in the same USB port, and transfer audio digitally, then it must have some sort of OTG functionality too.
Interesting. In that case, does the receiver distinguish from mass storage and OTG via impedance (or some other physical electrical quantity), or by communicating with the device? I know that Arduinos have Apple Accessory libraries that allow it to be recognized as an Apple accessory, so I'm guessing that the communication protocol is what cues the receiver?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Creating a iphones/ipods sound system for univeristy project Vettel Construction Tips 6 2nd March 2011 05:16 AM


New To Site? Need Help?

All times are GMT. The time now is 06:41 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2