Q: Is there a dock for the iPod touch 2G that will allow me to connect my external headphones as if the iPod wasn’t on a dock? Seems all the existing docks have only a line out with no headphone amplification capability.
A: The output from the iPod Dock Connector is intended to be a “line-out” level output which bypasses the internal headphone circuitry on the device.
Theoretically this provides cleaner sound output when connecting to your own speakers or stereo system, since your signal is not passing through two different amplifiers.
Apple’s own Universal Dock provides volume control, but it should be noted that this attenuates the volume, rather than amplifying it.
In other words, it does not include any amplifier circuitry, but simply allows you to reduce the volume based on the iPod’s own volume settings. Since these docks require an Apple authentication chip to communicate the volume control signal with the iPod itself, most third-party manufacturers have not chosen to implement this feature on their own docks.