background hiss, mains hum, and hi freq noise, where do they come from?

plonkywonki

plonkywonki

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Hi,

I've renewed my interest in the sounds in found in dead silence with an amp on reasonable our louder level, and what you then can hear in an amp's background noises, sometimes only via the headphone output. Everything just seems to "live".
I talk about background hiss, mains hum, or high frequencies that can be made audible. I'm totally aware that all systems make noise and produce hiss, hum etc.

For me one thing is curious though, I notice in various systems that there seems high pitched interference being picked up, that goes on and off in a slow wave / cycle, what is this?
Further I wonder does anyone try to surpress it or just leave it as is? Just curious about our common thoughts on this subject matter.
 
Hum is almost always a grounding issue.

Hiss - some amps have more than others. Usually totally inaudible in normal listening. No clue what causes it other than amp design (pre-amp, source etc). I actually find that many amps that have some hiss - like if you turn it up all the way its a little there - are more musically engaging than the totally quiet ones. Not always but ....

Still have no reason why tho.
 
Not exactly sure from your description what you are talkingabout.

I'm sure we'd all agree though that any noise not inherent to a component we'd try to eliminate.

There is a vast amount of devices designed to help eliminate noise. Manufacturers of audio gear go to great lengths in general to eliminate noise in their products.
 
Some interference sources do come and go, fade in and out. These are often caused by WiFi equipment nearby. WiFi can run high power and transmits intermittently in short bursts, or packets. Ethernet and USB do the same thing but is usually less of a problem.
 
To support above, I listened closely (but with no music playing of course) to my amp i.e. my lovely Hegel.
As a basis, in the speakers you hear just a small hiss, assume below -100dB or even lower. This is inaudible from 1m distance and up. Present but no issue.
Further nothing else in speakers.
Headphone output seems (always) more noisy somehow. In the headphones @ volume max I hear, slight earth hum. I tried with ALL other mains switched off but this hum remains. It is also far below listening levels (ref I'd listen at 20/100 max and not 100/100). 2nd I notice a high frequency when amp gain is above unity i.e 85/100 up to 100/100. Unclear to me what this is. Maybe radio/wifi signals picked up from neighbours or noise on the power net?

Note I experience(d) exactly the same in other brand amps and in other locations.
 
plonkywonki said:
To support above, I listened closely (but with no music playing of course) to my amp i.e. my lovely Hegel.
As a basis, in the speakers you hear just a small hiss, assume below -100dB or even lower. This is inaudible from 1m distance and up. Present but no issue.
Further nothing else in speakers.
Headphone output seems (always) more noisy somehow. In the headphones @ volume max I hear, slight earth hum. I tried with ALL other mains switched off but this hum remains. It is also far below listening levels (ref I'd listen at 20/100 max and not 100/100). 2nd I notice a high frequency when amp gain is above unity i.e 85/100 up to 100/100. Unclear to me what this is. Maybe radio/wifi signals picked up from neighbours or noise on the power net?

Note I experience(d) exactly the same in other brand amps and in other locations.
Click to expand...

If you are hearing -100dB, you are not human :P
 
TheOctopus said:
If you are hearing -100dB, you are not human :P
Click to expand...

I live in orbit, right? :audiophile: But it was an estimate, as I needed to push volume to above unity before such things get audible. With amplification you can make audible everything. Everything audio is a well balanced mix between signal and noise and in the example the ratio was skewed on purpose. But still everything you can make audible I'd love to understand it's background from.
 
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