Hiss from speakers when Atom is turned OFF

Amp: Naim Unity Atom
Speakers: B&W 603 S2 Anniversary Edition

When I turn the Naim Unity Atom off (to standby mode), after about 10 seconds my speakers will start making a constant hissing sound.

I read in another post that this is “normal”… But why is this normal? It is an annoying and very noticable disturbance when you live in a small apartment. And when you pay +3000$ for an amp, this is not exactly what you expect…

Is there any way to avoid it??

I mostly have the problem after I have used the HDMI input, and then have to turn the naim unity atom on and off 2-3 times before the speakers stop hissing.

Do you have something plugged into the USB slot and/or do you have server mode set to on in the setting in the app?

If either is true the unit will stay powered on. Try removing the USB drive and turning off server mode and see if the hiss is still there.

What does concern me is that the hiss should not be noticeable enough to provide a disturbance unless you are close to the speakers. Mine (on a Star) I only hear if I get pretty close to the tweeter. If it is really audible it is perhaps time to contact your dealer.

That said as for normal hiss and the unit staying on. Slight hiss when idle is a Naim thing and on all Naim amplifiers. And a unit remaining powered up remains warmed up and actually leads to better stable performance all around.

It is normal for the Atom to hiss softly even in standby.
As far as I know, the only way to avoid it is to turn it off at the mains.
Mine’s in a large room so I never notice it.

Oh one more thing. There is off and off on a Uniti device.

If you hit the power button and release it goes into sleep, which means stuff that should be powered on according to the settings will remain on.

If you press and hold the power button till it flashes and you hear the transformer relay click off it goes into deep sleep and in this state there should also not be any hiss even with USB connected or server mode selected. It will, however, take a little longer to start up again later that with a normal sleep and you wont be able to discover it on WiFi.

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I never knew about the deep sleep. Thanks for enlightening me :slight_smile:

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It’s a bit handier than having to pull the power cord LOL

I never use this aside from rebooting the device. Something it solves little software issues by rebooting via deep sleep so I don’t have to power cycle. I just leave both my Uniti’s in sleep mode and with the USB connected. Keeps them nice and toasty.

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Thank you for the explanation. Always interesting to learn why it is so.

I do not have USB plugged in or the App in Server Mode, so apparently what I am experiencing is “normal pre-heating” of the amp, as you mention.

Well I have a small living room and I like to read in the evenings, so when sitting 3 meters away from the speakers, reading, I notice the hissing. But good to know that I can just press and hold the power button to kill the hissing.

Maybe I am just very sensitive to sounds/noise.

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Hmmm nope, in that case the transformer should also switch off in normal sleep. I vaguely remember reading that HDMI could also keep the unit alive. Maybe it is worthwhile to plug out the HDMI cable then and see. I could be wrong though.

I also use HDMI but in a test I did quite a while back my Star’s transformer switched off when I unchecked Server Mode and unplugged the USB.

Cannot find the references again, perhaps @Naim.Marketing can confirm.

Yes it only happens when I power off the unit while “HDMI input” is selected. When I use Tidal, internet radio etc. no hissing occurs.

These are my app settings.

*When I use Tidal, internet radio etc. and then power off the unit, no hissing occurs.

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Hi all,

I am new to the forum. I figured out that the standby hiss only occures when either upnp is on or an external usb device is connected, basicslly the system needs to keep internal stuff running.

now there is no hiss anymore when i do not use usb or upnp.

Hope there‘ll be a software fix soon.

Greetings from Germany,

This is intended functionality.

The device has to be on in server mode.

The hiss can be more apparent with more sensitive speakers and different tweeter configs. I don’t hear mine at all since getting my ProAcs unless I am right up to speakers and even then it’s not very loud. With previous speakers I could hear it from my listening position when it was quiet they had concentric drivers and where higher sensitivity.

My speakers (klipsch forte3) have a hiss. just when whole system is muted i can hear it slightly from my listening position.

I cannot read a book when server mode is on. So i had to switch it off.

Would you say it is a mismatch to pair high efficiency speakers to the atom?

I would say that this is a possibility, noise may be more apparent because the speakers are able to reproduce it from the very low level signal. I have noted that a similar issue can occur when listening through a headphone amplifier using very efficient in ear monitors.

I also note that the switch on thump with my current speakers ATC SCM 40’s is much less than my previous more efficient home made efforts!

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I don’t think it’s a mismatch in performance, it’s just something you have to accept when no music is playing, given that Klipsch speakers are particularly sensitive. At least the Atom gives you an easy way to silence them unlike older Naim designs.

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Very high-sensitivity speakers like horns are definitely more problematic there. The Klipsch Forte III have 99 dB, so roughly double volume for the same input power than a more common 90 dB sensitivity. Hence the hiss will be more noticeable, as you found

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Could it be that in the input settings you have ‘HDMI Auto Switching’ set to ‘On HDMI input’. That would explain why it only occurs if you’ve used HDMI last. Otherwise it’s strange that it’s so inconsistent.

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Every 3dB is a doubling of sound energy, so a 9dB difference equals 2 x 2 x 2 = 8 times more energy. It doesn’t always translate into a 8x louder sound ofcourse, but it can be close depending on the type of sound that is amplified!

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While indeed +3dB is technically twice as loud, I think there’s a rule of thumb that says about 10dB is what humans perceive as twice as loud. So 90 → 99dB could be described as twice as loud.

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