Q: I have a fourth-generation 20 GB iPod that I use in my car with a Dock Connector that was installed to share the satellite input. I’d like to replace it with a larger capacity iPod but I don’t want to lose the ability to use the Dock Connector which did not work with my first-generation iPhone and will not work with an iPhone 4S. Is there an adapter I can use with a current generation iPod classic? Or what is the latest generation iPod I can use with a Dock Connector that works with a 4G?
A: For the purposes of analog audio playback the 30-pin Dock Connector has remained essentially unchanged since it was introduced with the third-generation iPod in 2003. Any properly designed speaker system or other accessory that simply plays music via the Dock Connector should work fine for that purpose on all iPod, iPhone and iPad models that still include the 30-pin Dock Connector.
Beyond simply providing analog audio output, however, the issue gets somewhat murkier, as the standards for data transfer and charging have changed a couple of times over the years. Specifically, the original Dock Connector on the third-generation iPod in 2003 only supported charging from a 12V FireWire power source; this was later expanded to allow for either 12V FireWire or 5V USB power with the iPod mini and fourth-generation iPod, and continued across all later iPod models, and even the original iPhone, until the release of the iPhone 3G in 2008. From this point onward, 12V FireWire charging was dropped from all subsequent iPod and iPhone models with the notable exception of the iPod classic, which has basically only received modest design changes anyway since it was first released in 2007.
For data communication over the Dock Connector, the third- and fourth-generation iPod and the iPod mini supported both FireWire and USB data transfer in 2003 and 2004; the fifth-generation iPod and original iPod nano dropped this support to USB only in 2005, which continued on with all subsequent iPod models as well as the iPhone and the iPad.
What this means in practical terms is that if your in-car system simply takes audio from the Dock Connector it should work fine for playing audio from an iPod classic or even any iPhone or iPad model—subject to physical size limitations, of course. It is unlikely that it will continue to charge any newer iPod models except for the iPod classic, which still continues to support 12V FireWire power. You can also power an iPhone, iPod touch or iPod nano simply by using a third-party FireWire to USB charging adapter such as the Scosche Passport.
If your in-car system actually reads data from the iPod, which many do in order to display on-screen menus and playlists for example, then compatibility will depend on whether your system was designed to communicate with the iPod over FireWire or USB. However, FireWire was only supported for data communication via the Dock Connector for a two-year period, with USB also supported for that entire time, and has not been supported in any iPod model sold since mid-2005. Therefore, in-car systems that use FireWire to communicate with an iPod would be relatively uncommon. If you do find yourself in this situation, you should consider upgrading or replacing your in-car system if at all possible, since the only other option is to mess with expensive ($200+) and relatively obscure FireWire-to-USB adapter solutions. Some companies sell simple and inexpensive FireWire-to-USB pin adapters, but these border on being snake oil and will not only definitely not work, but may even put your equipment at risk; FireWire and USB are completely different communication standards that can’t be converted with a simple pin reconfiguration any more than you can plug a coaxial television cable into your headphone jack to listen to cable TV audio.