Static issue with some new iPods

iPodlounge.com is reporting a problem with some new (4th generation, Click Wheel) iPods where static/noise can be heard through the headphone jack when the iPod's hard drive is accessed. This generally occurs when the iPod is transferring data from its hard drive to its RAM buffer (for example, after extended listening or when skipping songs frequently).

The issue is clearly not affecting all new iPods -- a MacFixIt editor has one of the new models and has not experienced the problem, and a majority of respondents to the iPodlounge story note that their iPods don't have it -- and may in fact only be affecting a very small number of users. However, there have been enough reports that it appears this is more than an isolated issue.

Unfortunately, it's difficult to accurately assess how many iPods actually exhibit this behavior, as it's only observable in specific circumstances: in a quiet environment (or using headphones that isolate external sound), with the iPod hard drive spinning, and using headphones with high efficiency and good reproduction of detail. In noisy environments, the static may be masked by external noise. Similarly, whereas headphones with significant isolation, high efficiency, and detailed resolution -- such as the Shure E2c or E3c or Etymotic ER-6 or ER-4P -- make it very easy to hear such static, many other headphones may not reveal the problem. Finally, even in the "ideal" circumstances, users with less than perfect hearing may have a hard time detecting this noise, which, by all accounts, isn't loud.

(iPodlounge also cautions users not to confuse this problematic headphone noise -- present in only some new iPods and apparently transmitted through the headphone jack -- with the normal sound of the iPod's hard drive, audible if you place the iPod itself near your ear.)

Hardware or software? The issue appears to be isolated to the iPod's headphone jack; the dock connector, which provides a line-level audio signal, does not exhibit the problem. However, during testing with a user whose iPod has this problem, we've concluded that it's most likely not a feedback issue between the hard drive and the iPod's actual headphone jack: When using the iPod in FireWire disk mode with headphones connected, the static is not present, indicating the noise is somehow contained in the audio signal, not the headphone jack itself. This leads us to believe that the problem is assocated with the iPod's headphone amplifier and/or audio circuitry. If true, this is encouraging, as it means it's more likely that the issue can be fixed with a simple firmware update. (Although without knowing more specifics, we can't make any definitive predictions.)

That being said, some users have speculated that the issue is simply one of grounding: on some iPods, the headphone jack is too "flush" and some headphone plugs are thus coming in contact with the iPod's metal case. We haven't been able to test/verify this, as we don't have any iPods that exhibit the problem.

Apple aware of the problem? One iPodlounge reader posted the following in the comments section of the iPodlounge article, indicating that Apple is aware of reports of the problem:

"After speaking with Apple support, i was told that they were aware of the issue, that it is due to caching of a track, don't intend for that noise to be audible, and to 'be patient, be vigilant and watch for updates.'"

We'll keep you updated as we learn more.

Are you experiencing this issue? Drop us an email at Late-breakers@macfixit.com.

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