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Old 29th January 2012, 11:14 PM   #1
juanito is offline juanito  Europe
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Default USB dac and ipod question

Is it possible to plug an Ipod with the USB cable to an USB DAC? Will sound go via the USB cable and then to the DAC?? not sure, I whant to buy a DAC or something to swich between my amp and a MP3 device, such as the Ipod and a Sony. But I have the impression that it will only work via minijack...
Can any body help please with this issue? I was planing to get a lampucera board.
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Old 31st January 2012, 03:37 PM   #2
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Nope.

Digital stream can only be accessed from the dock, and only if you have the secret code from Apple that they give to certain manufacturers. There are a few "digital" docks like the Onkyo ND-S1 and the Pure i20. None of these are built for portability.

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Old 31st January 2012, 03:58 PM   #3
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Buck has it exactly. You can hook a USB DAC up to your computer, but the only way to hook it up to your iPod is through a docking station with the special Apple decoding hardware. There are by my count about five of these out there now (Onkyo ND-S1, Pure i20 and Wadia, plus a couple of higher-priced products). None are portable or designed to be.
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Old 31st January 2012, 04:02 PM   #4
GloBug is offline GloBug  Canada
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Well there is a project for somebody.
It sounds similar to the tricks they use for charging the devices. It might just be a matter of applying a certain voltage to a certain pin(s).
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Old 31st January 2012, 09:29 PM   #5
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The way it's been talked about, it sounds like more of a digital handshake or key. The killer app would be a portable doc/dac/headphone amp that would cradle the iPod and not be too big and bulky.
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Old 31st January 2012, 10:01 PM   #6
juanito is offline juanito  Europe
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Thanks!! I've been searching and arrived to same conclusion: now confirmed. If it's not the wadia is the onkyo and pure. I'm surprised that chinese haven't discover it yet. I thought ebay would be full of these docks, but nope. I'm looking other docks that may use this same digital out put without D to A conversion. Pro-ject and creative may have some similar docks too.
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Old 31st January 2012, 10:40 PM   #7
Nanook is offline Nanook  Canada
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Default the "handshake"

AFAIK, if you purchase an item that states "made for iPod" whatever the iPod looks for is there. Then access the pins. You can purchase new cable sockets cheaply.

I have a YBA "designs" iPod dock. It is "made for iPod". If I can add a few wires and take them to the correct pins, then I should be able to digital out. So far it has eluded me.
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Old 2nd February 2012, 01:09 AM   #8
qusp is offline qusp  Australia
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no, that is not correct and that is why its not working for you, in order for this to work, the ipod must be slaved to the dac, the ipod cannot act as a USB audio host as the standard protocol requires the host to provide power to the slaves transceiver (and dac if its usb powered) and being portable devices with limited battery life and limited current capability as host, this option is not enabled.

there is already 2 semi portable devices which do this around for a bit over a year. one is called the CLAS (Cypher labs Algorithm solo yes they spell it wrong) which is just a dac only (Wolfson) and has spdif output also, not cheap and from reports doesnt measure so hot, but sounds decent; another is by Fostex, who also have a number of new recording/live performance solutions using ipod or ipad. the portable unit, which is a bit more compact than the CLAS is called the HP-P1, but this contains an AKM dac and built in headphone amp, as well as some ability to set pcm filter settings. both of these devices act as both USB and i2s master; it is unclear whether the transfer is synchronous or asynchronous, but strangely it would appear the former rather than the latter.

the ipad is a slightly different story, you can use this with the apple camera connection kit to connect to certain usb 1.1 and 2 dacs, as long as the transceiver and dac/amp is either self powered and sets this register, or has a transceiver that has sufficiently low current draw as to stay within the current limit set by the ipad. it will of course not work with any dac that uses a driver that is not the native USB audio codec.

hope that helps. none of this is written out for the general public, so there is probably some details i've missed or are perhaps incorrectly stated broadly. much of the above info has been discovered by trial and error over some years by those like myself who are involved heavily in high quality 'portable' headphone audio (inverted commas because some of the rigs are not pocket sized and come under the heading transportable audio)

fostex HP-P1



CypherLabs CLAS


it is true that the idevice dock contains several accessory enable pins that will enable connection to a raft of different devices including chargers. it uses a system of pullup/down resistors to set registers. but that by itself this will never enable connection to a dac

for home there are several solutions as already mentioned and with ipad you can likely use the camera connection kit depending on the usb input of that dac. you can also access the lineout (analogue) via the dock at the bottom, the exact pinout for enabling the lineout will vary depending on the model ipod/ipad

Last edited by qusp; 2nd February 2012 at 01:28 AM.
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Old 2nd February 2012, 01:18 AM   #9
GloBug is offline GloBug  Canada
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That was very good.
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Old 2nd February 2012, 01:34 AM   #10
qusp is offline qusp  Australia
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thanks its something of a black art still, the required info is only available officially under NDA and license agreement that covers both the hardware/software, but also because you are exposing the digital stream, copy protection for the music.

part of my business (actually a pretty large part) is making bespoke compact/low profile LODs (Line out docks) to gain analogue line level for portable headphone amps and in the case of the 2 devices mentioned above, USB digital audio. that along with headphone mods and recables forms the core of my every day business, but i've begged and borrowed all the info to do this, I dont have 'made for ipod' status, but rather a custom niche one man business that started out as a hobby.
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