A number of contributors to a leading audiophile forum have warned that the latest 1.1 iPod firmware update comes with some potentially nasty side-effects.

According to several members of head-fi.org, the 1.1 update affects the power circuit of the 80GB and 160GB iPod Classic models, causing DC offset in both the headphone jack and the docking port. One member claims to have measured this at 500mV – even when the iPod had been manually shut down.

Clearly, the consequences of an iPod sending electrical impulses through its two external ports aren’t going to be good. If the reports are indeed true, then affected iPod owners could experience a reduction in battery life, plus a loss of sound quality. Several forum members have already reported hearing 'hiss' and 'buzzing' on their updated devices.

The most worrying aspect though is the affect the alleged power surges could have on sensitive headphones or hi-fi equipment. As one member puts it, “it could cause permanent damage. You generally wouldn't connect your headphones to a headphone amp unless it had less than 10mV of DC offset – 500mV is really a lot.”

And, of course, if you regularly connect your iPod to an expensive hi-fi system through its docking port then you probably don’t want your amplifier and speakers spiked with up to 500mV of DC current at regular intervals either.

As usual, Apple remains tight-lipped about the alleged bug. But iPod owners may well want to hold off any firmware upgrades until the situation becomes clearer.