Noise

When there is nothing playing but you system is powered up, is there complete silence or is there “hissing” coming out of your speakers?  My six figure Naim system has distortion (hissing) coming out of the speakers.  Of course when the music is playing it is drowned out.   Is this the norm?

 

Original Post
Huge posted:

It's not from the quiescent current of the driver transistors or output stage, it's not from the mains...

It's from the long tailed pair at the input to the power-amp, or the buffer amp following the volume control of the pre-amp.

so, in layman's terms--don't worry about it.   The system has it's own dedicated circuit, fancy $1000 power cords, and a $4000 surge protector and it still hisses.  My 1977 Marantz receiver, thoren turntable, and Klipsch speakers is absolutely quiet, my Naim is not---drives me crazy.  

Indeed, provided you can't hear it from the listening position, don't worry about it, it's normal for some designs (such as Naim).

If Naim were to design out the low level of noise, doing so would have a detrimental effect on sound quality (but quite how much detriment is difficult to say - the difference may actually be quite small but Naim's philosophy is to always maximise sound quality).

It is from the first high-gain stage. In my system it was the 552 Pre - it is normal and nothing to be concerned about. I know it was the 552, as when I went to the S1 Pre that low-level noise reduced in level, as the S1 is a bit quieter, as perhaps you may expect for the price difference.

It never bothered me over many years use with the 552.

DB.

Zackwater posted:
Adam Zielinski posted:
Zackwater posted:

Only hear it when I’m close to the speakers.  From the responses I guess it’s normal.   

Do you also hear it when the system is muted?

yes, same noise.

Actually - if your system is properly earthed, there should be no hiss whne the system is muted.

Hiss-on-mute may be indicative of inproperly earthed / grounded mains.

Adam Zielinski posted:
Zackwater posted:
Adam Zielinski posted:
Zackwater posted:

Only hear it when I’m close to the speakers.  From the responses I guess it’s normal.   

Do you also hear it when the system is muted?

yes, same noise.

Actually - if your system is properly earthed, there should be no hiss whne the system is muted.

Hiss-on-mute may be indicative of inproperly earthed / grounded mains.

Hmmm, actually hiss is generated in the power amp itself as thermionic noise, though should be at a very low level and in a good amp and normal efficiency speakers only just audible right by the tweeter or midrange drivers. That is different from hum, which is related to mains which indeed is lilkely to be indicative of earthing issues, a fault, or poor shielding.

Muting in the preamp, or reducing volume control to zero, will reveal the power amp hiss. Unmuted with volume control on max will reveal hiss from preamp (and anything connected)

Eloise posted:

Of course if you’re in some places (less an issue in U.K.) you should also check there’s not a snake crawled into the bass port of your speakers if the hiss changes or appears more from one speaker than the other!

:-)

Or, if there is no bass port, a snake on the sofa next to you (one each side if the sound is balanced)...

Innocent Bystander posted:

Hmmm, actually hiss is generated in the power amp itself as thermionic noise, though should be at a very low level and in a good amp and normal efficiency speakers only just audible right by the tweeter or midrange drivers. That is different from hum, which is related to mains which indeed is lilkely to be indicative of earthing issues, a fault, or poor shielding.

Muting in the preamp, or reducing volume control to zero, will reveal the power amp hiss. Unmuted with volume control on max will reveal hiss from preamp (and anything connected)

You'll only get thermionic noise with a thermionic (i.e. valve) amplifier.

With solid state amps the noise sources are shot noise (statistical noise) and Johnson noise (thermal noise).

Muting the pre-amp and turning the volume control to zero remove the effect of any noise sources from the volume control and all previous elements in the chain (i.e most of the pre-amp and source components).  What remains are:
The buffer amp of the pre-amp (the line driver which follows the volume control and is usually unity gain)
The input long tailed pair of the power-amp (balanced current amplifier)
The gain stage of the power-amp
The output structures of the power-amp

The first two of these are by far the most likely sources of any hiss.


But yes exactly right that the hiss should only be audible very near to the speakers and about grounding (and other mains related) issues causing mains hum not hiss.

Eloise posted:

Of course if you’re in some places (less an issue in U.K.) you should also check there’s not a snake crawled into the bass port of your speakers if the hiss changes or appears more from one speaker than the other!

:-)

I would also expect that the sound would be much more etiolated if that happened.

Beachcomber posted:
Eloise posted:

Of course if you’re in some places (less an issue in U.K.) you should also check there’s not a snake crawled into the bass port of your speakers if the hiss changes or appears more from one speaker than the other!

:-)

I would also expect that the sound would be much more etiolated if that happened.

That's stretching it a bit!  

Isn't the hiss, when unmuted, a result of the very high input sensitivity of most Naim pre-amps (75mV)?

(NAC S1, as mentioned by Darke Bear, is, I believe, a 'more sensible' 250mV?)

My system gives hiss, audible only when when close to the loudspeakers, irrespective of volume control setting, but is silent when muted.

(Speakers that are currently in use are 87dB/W/1m, according to the manufacturer's spec., but, according to any reviews I've seen, 85dB/W/1m in reality)

It will hiss - muting will reduce the hiss as the amplifier is not amplifying any noise from the source but won't eliminate it completely - how much you notice it depends on the sensitivity of the speakers and how good your hearing is / distance from the speaker.

If it was clicks and pops, buzzes or hum then I'd suspect issues elsewhere but from the OP's comments, this isn't the case and is nothing to get concerned about.

james n posted:

It will hiss - muting will reduce the hiss as the amplifier is not amplifying any noise from the source but won't eliminate it completely - how much you notice it depends on the sensitivity of the speakers and how good your hearing is / distance from the speakers.

I disagree with you James. Now that I have dedicated mains circuits, no noise comes from speakers on mute (on either of my 4 Naim systems at home). When I unmute, a gentle 'hissssss' comes from the tweeters - tells me that the system is alive and ready for some action

Huge posted:
Adam Zielinski posted:

Guys - how is the above helping the OP???

His rig hisses - wheather on mute or not. To me that is a sign of a mains earthing (lack of a 3rd yellow-green wire).

Hiss has nothing at all to do with mains grounding.

My experience is completely different. Hence my response - not a guess, but based on hand-on-experience.

Adam Zielinski posted:
Huge posted:
Adam Zielinski posted:

Guys - how is the above helping the OP???

His rig hisses - wheather on mute or not. To me that is a sign of a mains earthing (lack of a 3rd yellow-green wire).

Hiss has nothing at all to do with mains grounding.

My experience is completely different. Hence my response - not a guess, but based on hand-on-experience.

If that's the case then there's another major problem with that amplifier!  (This is based on experience of understanding, designing and building amplifiers!)

Huge I think we know. The reason why I mentioned a mains issue (after Adam though) is that it is at least not clear to me if the OP understands all the different variations on hiss, buzz, hum etc. I agree to all the things you and IB mentioned.

In my case, I always have the hiss (normal on all Naim systems) but also a very soft buzz which is either caused by my inbuild microwave in the kitchen or the inbuild transformator for some light bulbs. Sadly, I cant get rid of them without breaking things. I should start a poll on this forum whether it is expected to be the microwave or the bulbs ...

Hi Ardbeg,

I don't think the OP is confused about hiss vs hum, but maybe a little confused as to the distinction between noise and distortion.

Is your hum through the speakers or from the transformers of the PSUs in the components themselves?

In terms of the 'transformers' (actually they're probably SMPSs) for low voltage lighting, then these won't have any effect when the lights are off (no current = no power = no EMI), also the main house lighting will be on a completely different circuit to the mains power distribution making that a less likely source of interference.

For the microwave, there should be an isolation switch somewhere in the kitchen, try turning it off using that and see if the hum goes (if not it's something else - of course it could always be coming in on the mains supply from outside your house).

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