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What causes hiss?

post #1 of 9
Thread Starter 
Easy question for those in the know.

What causes hiss?

I've got a few things that hiss like woah with my ER4P (its a bit like really loud tinnitus or walking through one of those scanners at shops with your headphones on), and my Sansa Clip doesnt have any audible hiss.
post #2 of 9
All electronics have a certain background level of noise. (Read about "thermal noise" for more info) If an amplifier has enough gain (amount of amplification) and/or your phones or speakers are sensitive enough you will hear the amplified noise as a constant background hiss.
post #3 of 9
oops, double post!
post #4 of 9
ground lloop
post #5 of 9
poor quality amplification or ground loop (though usually more of a buzz than hiss) or dirty power source
post #6 of 9
Ground loop does not make the noise he is describing. He is describing thermal noise which is a white noise like hiss.
post #7 of 9
Its a good question.

My system was hissing the other day. I assumed my valve pre amp had bust a valve (again) so I swapped all the valves one at a time and it was still doing it. I thought I was going nuts, I couldn't find anything wrong. Turns out the power chord wasn't pushed fully into the power amp. Doh!

the cause for hiss I think wikipedia have something about it, apparently some white noise picked up by radio /TV is leftovers from the big bang. If you're into the math I reckon quantum physics could be a go.
Noise (electronics) - Wikipedia, the free encyclopedia
post #8 of 9
Thread Starter 
Quote:
Originally Posted by Budgie View Post
Ground loop does not make the noise he is describing. He is describing thermal noise which is a white noise like hiss.
Yeah, definitely not a ground loop. I am familiar with the groundloop sound.

I know it's due to poor quality amplification, as its just an extra on a piece of hardware I have (it has line outs that are totally clean). I'm not sure if it has to do with gain or not, because its always the same volume regardless of the volume i set to the headphone out.

It could be thermal noise, as as I have said the volume is the same regardless of the voltage applied (volume knob doesnt affect it), but it certainly doenst sound equal throughout the spectrum. The sound(s) produced are above 6khz.
post #9 of 9
If the volume control does not affect the noise's level, it is because the source of hiss is after the volume control in the amplifier circuit. Usually a volume pot is at the input of an amplifier, so I suspect the amplifier is the source of the noise, which would not be unusual. Are you sure it is band limited to above 6k, or does it just sound like it is? I know when I listen to white noise (like the FM interstation hiss shark jump mentions) It does not sound like it is full spectrum, even though it is.

edit - This Wikipedia page has a sound file you can compare to-
http://en.wikipedia.org/wiki/White_noise
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