iPod touch 4 limited like iPhone 4
While built-in cameras and a microphone are exciting additions to the newest iPod touch, the same I/O limitations that plague the iPhone 4 as an audio/acoustics analyzer platform remain. In other words, the existing audio inputs on the 4th generation iPod touch suffer from significant low-frequency roll-off, just as the other iPhone and iPod touch models do. Also, existing analog line-level input accessories that worked with earlier iPod touch and iPhone devices (before the iPhone 4) are not compatible with the latest iPod touch.
In spite of the present limitations, however, I’m sure it’s only a matter of time before suitable input options become available for the latest and greatest iOS devices…