The Wadia 170i transport is recognized as the first non-Apple unit to get digital sound out of an IPod in about 2007-8. They stated that a USB connection will not suffice. It takes Apple authentication going into the IPod for it to bypass the audio analog lineout and send out digital audio. The USB connection clearly sends out digital non-audio data for the display. Perhaps the simple question is there an Apple authentication chip or some equivalent in the car headunits to get digital audio, not just digital nonaudio data for the display? Pins 3 and 4 in the 30 pin connector give analog line output which bypasses audio manipulation that would come out of using the earbud port, but is not digital and does not bypass the IPod DAC.

Quote from Wadia Digital.
'"I thought it was impossible to bypass the iPod's DAC. "So did we," said Wadia president John W. Schaffer. "Then we discovered the little-known fact that Apple had a process called 'authentication' that allowed mobile electronics companies to bypass the iPod's internal DAC."

"Authentication" refers to Apple's authentication chip, which essentially tells the iPod that it's okay to output raw digital audio or video data to the chip-enhanced component. The authentication chips are only available in Apple products or from products made by Apple-licensed third-party developers. After Wadia first began developing what became the iTransport, Apple opened up the authentication program to more third-party vendors. The iTransport may be the first audio product of its kind, but it probably won't be the last. But however you slice it, being firstest is a great coup.

"I think Apple approved our working on the iTransport because of our reputation as a high-end component manufacturer. Apple thinks of the iPod as a high-end source, so it made sense to them," said Schaffer."'

Cambridge and Onkyo have done similar, and give similar explanations.

Any car headunits really get digital audio from the IPod, not just the digital data display? Do they explain how? I have seen some advertisements but they did not distinguish digital audio from USB data, they seem to assume that they are the same.

 

I don't really know but Alpine uses a single usb and has a 24bit dac built in. That leads to me to believe it is a digital signal.

Kenwood uses usb with a separate audio connector which I always assumed was analog since it is 3 pin. But then Kenwood also uses a single usb on models.

 

Car units have DAC for other functions such as ditigal MP3 and CD, not just IPod. From the information from Wadia, and similar from Onkyo and Cambridge, and Pure it seems that either digital or analog can be brought out of the USB. Depends on the authentication chip from what I can read.

 

from alpine website

 

I just looked up a usb connector, it only has 4 pins. For some reason I thought they had more.

With only 4 pins, you need power, ground and data +/-, there would no pins left over. Looking at it that way, if all there is only a usb connector, you would have to get a digital signal over the usb data.

 

In that case then all USB connections to IPod are digital sound. How did/does Wadia and the others sell anything??? The units with authentication chips have been tested by ear, and equipment, on HiFi sites and seem for real. I could be makeing false assumptions, but would like to understand. If USB connection is automatically digital audio, then what happened to authentication? I was aware of the Alpine quote and some other companies, and looked at the USB pins. Car headunits do not claim the authenticaiton chip. I am trying to get an explanation of seemingly contradictory facts by Wadia vs the car headunits manufacturers/sellers about digital audio.

 

interesting @ that description from alpine

When u hook em up via usb, it's still using the shitty dac in the ipod itself. I doubt it's bypassed on an analog signal.