I'm just playing around with my new iPhone, and as an iNoob, I probably have a hard time understanding the differences between SoundCheck and ReplayGain (which i'm quite familar with).

I'm using headphones that really needs a bassboost, so i'm using the bassboost EQ (not sure what it's called on english iPhones). When this is enabled, almost every track is extremely distorted, even though the volume is not turned all the way up. In theory this should leave some headroom for EQ amplification.

I have enabled the 2nd option under iPhone, iPod properties ("Lydkontrol" in danish) - I'm not sure if it's related to SoundCheck or if it's similar to vlevel foobar2000-component? If SoundCheck-data are found, will they always be used?

I've read that mp3-gaining the files will help, and I'm almost certain that it will, but I'd like to get around this problem without altering my mp3's and changing my headphones if possible.

Generally I'm using foobar2000 with foo_dop component to transfer my music, but the problem also appears with purchases through iTunes-store.

Hope someone can enlighten me

I have an iPod Classic, I'm on my third iPod. EQ to me is all but useless, it does distort audio, especially loudness-war-victim songs. I don't see why it should matter (it doesn't anyway) whether the volume is not turned up, since clipping is occurring on the EQ stage, it's already distorted when it reaches the volume stage. Sound Check is also independent of the volume, since it works on line out.

There is a volume limiter, perhaps that's what you're referring to with "Lydkontrol"? That doesn't do anything but limit how far up you can raise the volume, it doesn't normalize or anything like that. Sound Check IMO kinda sucks. I think it's just a simple normalization. Sometimes it seems like there's more of a difference between two particular songs, instead of less. I think you can analyze with ReplayGain and then transfer those gain numbers into SoundCheck, but I haven't tried to do that yet. Others here should know better I'm sure.

My point was that if EQ did attenuate the sound or you were able to decrease the level before the EQ stage, it wouldn't matter, since I'm still able to compensate for that using the volumecontrol.


I don't think that SoundCheck differs much from ReplayGain in methology. The foobar2000 component uses ReplayGain values converted into SoundCheck values when it transfers them.

In my experience certain EQ settings will cause clipping on MP3s that are already close to 0 dB FS.

The only solution is to MP3gain all your files, this will mean the files are very unlikely to clip.

It may not differ in how it is applied. The big difference is how it is calculated and here iTunes has a different algorithm. As far as I know, if iTunes calculates the SoundCheck values, it does not use the loudness but rather peak values only.