Hey I'm new on the forum, but a bit of an audio freak so I wanted to post about EQ settings and stuff.

In case of a little crackle, the audio output went above 0dB (normal). So eighter you have an EQ setting with a frequency set to +1, +2 or more, or you use SRS WOW wich can push audiolevels above normal or the audiofile itself has peaks above 0.

Turn SRS WOW off.
Make your maximum EQ frequency 0 and make the others relative to that.
-(so in stead of 2, 1, 1, 0, 1 use 0, -1, -1, -2, -1).
If you still hear it, it's most likely the source file. You can use lot's of free and paid software to normalize music. Just don't normalize to 0cB, use -0.1dB as peak value or to be safe -3dB.

If you still have a crackle after that, try different headphone's. Might be a cheap product or a wire fail.

Odd things can happen. For instance, I have some PX100s which work wonderfully. High impedance, so low nastyness.

Still, I had a problem develop with crackling coming from the left side. Very odd.

Eventually I realised that there was a hair which had penetrated the foam on the left ear piece. It had dropped on to the the diaphragm and was vibrating, causing the problem. After extraction, all's well.

So, anything can happen. If you have PX100s or other pad phones and you have long hair, or sideburns like me (Elvis Lives!), then remember this one...

That's an interesting point. I have some Panasonic buds that I used to consider quite good (as buds go), but recently they have been distorting badly with deep bass notes. And I don't turn the bass up high. I guess that they aren't designed to work with high amplitude deep low frequencies that you can get from a direct-coupled headphone amp. It's not the clix, because it still sounds great with the Shures.

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Clix 2 8GB Red Line Zen Touch 20GB
Shure SE530 Shure E2C Creative EP-630

i got jbl220 reference and its quite the same as ep630 and i can tell you that if your running when youre using it the earphones or your touching it you can hear it and its pretty enoing maybe thats why...