Well I went and tried a few different firmware versions including some for different countries. However, like hakujin, the only version that records without the "cyclical noise" is the "iriver music manager" (IMM) version, (that's the and iFP-900(us)_V165 version below and, I guess, the same version developed for other countries will also work perfectly).
For what it's worth, if anyone wants to try those I didn't to make sure, I tried ifp900T(eu)-umsV13, iFP900T(jp)-umsV130, iFP-900(eu)_V185ums, iFP-900(jp)_V185ums and iFP-900(us)_V165 and iFP-900(us)_V165 was the only one without the squeaking.
Interestingly, the IMM version allows recording bitrates up to 320kbps at 44.1kHz where as the MSC version 1.85 (that allows file transfer plug-and-play usb use) only allows 96kbps at 44.1kHz (apparently the same as all the rest?) What's with that? Why is the latest IMM version so much better? The Latest IMM version and the Latest MSC version were released on the same date so one would think the quality of recording would be the same in both...right?
I'm now wondering if there will be a new firmware release where this problem could be fixed. I suppose that as the product has been discontinued iriver will have lost interest in developing the firmware?
It's a real annoyance because as well as a great radio and mp3 player, and in all other respects apart from the squeaking, a great recorder, it is incredibly bloody useful as a usb stick to move texts from uni to home and so on.
Looks to me like we're stuck with it, matthiaselmo. If you do find a fix let us know! Good luck. Anyway, I'm off to try rockbox on my new (secondhand) H320
