The Peachtree iDecco will bypass the Ipod's DAC and use its own Sabre DAC. I love mine not only for Ipod, but also for use as a DAC for CDs and even sound from the cable box sounds much better (for example, watching concerts on Palladia and other music channels). I also use it as a preamp.
You also may want to check the settings on the Ipod settings to make sure that the EQ is turned off.
You also may want to check the settings on the Ipod settings to make sure that the EQ is turned off.