Wondering if the hiss is in the recording. It seems like every single recording has some hiss, I think this is called a noise floor, and the louder you turn it the more you hear it. But on my ifuzen amp it seems louder then on the iphone 4. Could this be because its brighter? Its a little bit more hissy, even on dead silent parts. Would that be because of more treble emphasis. But if there is no other things going on, like no bass or anything except the hiss, i'd think it'd be the same.
How does amp hiss sound?
Even my iphone hisses a tiny bit. After you pause a song it hisses for like 4 seconds then it goes away. Its so faint you can barely hear it but it seems every noise source does this to a tiny extent. Is a trebly amp just amplifying that sound?
Impedence, if it does not have a compatible impedence, then it will generally hiss a bit. This is mainly more with the more sensitive headphones. Sensitivity does not directly equal a small impedence though but is generally a quality they will share.
Apple has a design where if no music or audio is played for a set amount of time ( a few seconds), then the whole amp circuit will shut off to save power and reduce that hisssing.
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Locate yourself in a completely silent environment, or as near to it as possible.
plug/unplug/plug/unplug your headphones with the volume down and no music playing. Now do the same with the volume up and no music playing. Whatever you hear as you plug and unplug is an artifact of the circuit, not the recording. It will typically sound like "SSSSSSSSSSSSS" or "SSSSSHHHHHH". In the case of AC hum in tube circuits it will be a "warmer" kind of sound "mmmmmmmmmm" around ~100 Hz or so.
A well designed circuit and a properly chosen headphone impedance load for that circuit should be completely silent.
Edited by kramer5150 - 1/19/13 at 11:07am
No. More powerful does not mean more hiss.
What is probably happening is that your headphones impedence does not match Apple's specs for their device. And thus it hisses.
If you get another large headphone and try it. You may find that there is no noise.
Large and powerful but low impedence amps are out there. The E12 I am listening to right now is an example.
I just tested some hissy 16 ohm IEM's with my 4S. There is a very small amount of hiss. Just barely detectable.
What is your question? How and why an amp may hiss has been described. Are you asking on how to stop this from happening with your current set up?