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Naim Uniti Atom Over heating


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Hi ,

I purchased hubby Naim Uniti Atom which is paired with KEF950 speakers last week for birthday.

He had a party yesterday and the system shut down after about 4 hours of continuous play, the message on the amp was that “it needed cooling”

For the most part the volume was ok, not blaring for those 4 hours  but the amp was working hard. It was in a room that allowed for air flow but it was a fairly warm day (Gold Coast )

Hubby said that the speaker cables were not great either, would this cause issues ? It is of great concern that a system like that only permitted 4 hours of play. I appreciate that it has the capacity to rectify over heating issues but to spend 5k on a system that works within limits is interesting. I would really like some feedback on whether or not I have purchased a product that is going to let us down. Is there something that we can do to ensure that the issue is not repeated. Hubby wants me to take it back today ! 
He did let it cool down for about an hour but same issue happened again so Naim Uniti was disconnected and put in the too hard basket.

I would appreciate some thoughts as i am not sure what I need to do.

‘many thanks in advance 

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:welcome:to the forum...

 

The KEF 950 speakers should have been OK to be driven by the Naim Uniti Atom.  Where was the Naim placed? Hopefully in a space which allow for lots of air circulation and not in a cupboard somewhere.  Sound quality can be improved with better speaker cables, but it is not likely to be the cause of the over heating.  Was there anything else connected to the Naim?

 

You may be unlucky and it could also be a faulty unit.  Take it back to the dealer and get it tested.  

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Hi Snoopy8,

 

It wasn’t in a cupboard or anything just sitting on a table in the middle of the room and nothing else was connected to it just the speakers and a network cable.It was a hot day , 29 degrees plus. When I touched the unit after it shut down it was hot, seriously hot so I unplugged everything as I thought it may implode. 
 

Thanks for the response.

 

 

 

 

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Kef q950 speaker specs https://clefhifi.com.au/catalog/product_info.php?products_id=4327&gclid=Cj0KCQiAmL-ABhDFARIsAKywVadBL5xsvJQ3skC6x9YJLOFzQH_8PQByGn1mA3rRW6la6PRuHF7oUb0aAmeyEALw_wcB indicate a not easy minimum of 3.2 ohm impedance amp load though good 91 dB efficiency so the question is the 40w into 8 ohm rated spec for the Naim amp able to play sustained loud levels. On paper it should be but it is not a generously powerful amp and the manufacturer gives no specs that I could easily find it is capable to 3.2 ohm and pumping out double the watts to keep up, which other more powerful and high current amps can do. 

 

The Naim looks reasonably well built at 7kg, class A/B amp circuit with large toroid power transformer and side heat sinks if that means anything at all but not knowing more than that it is hard to say. On the surface of it the Naim is a jack of all trades unit and not a dedicated powerful integrated or separate preamp and very power amp configuration that could be more capable for 3.2 ohm load speakers. $5k is a lot of money for such a unit and the extra cost is in the icon branding of the product vs lower cost common but potentially more powerful products.

 

 

0F8CD486-E041-4519-9BE1-55A0548E6EDB.jpeg

Edited by Al.M
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14 minutes ago, Pukara said:

Hi Snoopy8,

 

It wasn’t in a cupboard or anything just sitting on a table in the middle of the room and nothing else was connected to it just the speakers and a network cable.It was a hot day , 29 degrees plus. When I touched the unit after it shut down it was hot, seriously hot so I unplugged everything as I thought it may implode. 
 

Thanks for the response.

 

Sure it was a hot day, Justine - but any amp that isn't Class A should've been able to cope.  After all - you will get plenty of days at 29 deg or more.

 

I suspect that, as Al.M suggested, the Naim might have a problem with spkrs which drop to low impedance.  Yes, get it tested by the dealer - and as it appears the dealer sold you the spkrs as well ... you need to take them in too.

 

And how long are the spkr cables?  I ask because my Nap 250 used to shut down thermally, with 11m of Naim spkr cable attached.

 

If you can't shorten the spkr cables in your setup - the dealer needs to replace the Naim Unity Atom with a different device.  :(

 

Good luck,

Andy

 

 

 

 

 

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16 minutes ago, Al.M said:

Kef q950 speaker specs https://clefhifi.com.au/catalog/product_info.php?products_id=4327&gclid=Cj0KCQiAmL-ABhDFARIsAKywVadBL5xsvJQ3skC6x9YJLOFzQH_8PQByGn1mA3rRW6la6PRuHF7oUb0aAmeyEALw_wcB indicate a not easy minimum of 3.2 ohm impedance load and 91 dB efficiency so the question is the 40w into 8 ohm rated spec for the Naim amp able to play sustained loud levels. On paper it should be but it is not a generously powerful amp and the manufacturer gives no specs that I easily find it is capable to 3.2 ohm and pumping out double the watts, which other more powerful and high current amps can do. 

 

The Naim looks reasonably well built at 7kg, large toroid power transformer and side heat sinks if that means anything at all but not knowing more than that it is hard to say.

The Naim Uniti Atom is a good well built unit, supposed to deliver 45 Watts into 8 Ohms and 72 Watts into 4 Ohms.  Have to step up to the Nova to double the power.  

 

Suggest taking the Atom back to dealer to get it checked out first.  If there is nothing wrong, then need to make a decision on whether you want to upgrade to the Nova or get an alternative one box solution like the NAD M10.  

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Hey Andy

 

Speaker cables are about 4 to 5 metres each and yes I will speak to the dealer.


‘Thanks for the help

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15 minutes ago, Pukara said:

Hey Andy

 

Speaker cables are about 4 to 5 metres each and yes I will speak to the dealer.


‘Thanks for the help

It should not be an issue but how thin (wire gauge) are the cables or perhaps a pic to show.

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I will send a pic once I get home but they are the cheapest crappiest speaker wires that came from a friend until the other speaker wires were delivered.

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43 minutes ago, Pukara said:

Hey Andy

 

Speaker cables are about 4 to 5 metres each and yes I will speak to the dealer.


‘Thanks for the help

 

12 minutes ago, Pukara said:

I will send a pic once I get home but they are the cheapest crappiest speaker wires that came from a friend until the other speaker wires were delivered.

 

Aah, Justine - your Naim dealer may have an 'out' here!  :(  Although 4 to 5m is a perfectly normal length, if it is not Naim spkr cable then the cable might be what is causing the Uniti Atom to get hot.

 

(It depends whether modern Naim amplifiers use a different circuit to the old ones.  In the old days, Naim amps needed to 'see' spkr cables which had high inductance.  Naim spkr cable is built with 2 parallel runs of cable separated by a 'joining strip' about 10mm wide - which gives it its high inductance.  There's an intrinsic relationship here between a spkr cable's inductance - and its capacitance.  High inductance means low capacitance ... if the cheap crappy spkr wires you are using atm are actually high capacitance & low inductance - then they could be stressing the amp, causing it to get hot.)

 

Andy

 

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Hi Justine.

As  @andyr has mentioned the earlier Naim amplifiers  had, what was essentially a design fault, built in so that normal people and Naim geeks would buy and use their own branded speaker cable. This is certainly far less true today but there is a vestige of this design fault even in the latest models.

 

Naim has always claimed the dynamics mantra, but neglect to point out that they are not stable driving lower  impedances for extended periods of time.

The bottom line is that this unit is faulty and you should return it and demand a refund or replacement, because what you experienced should never happen in a competently designed modern amplifier, especially one that costs $5K. This is frankly, ridiculous and insulting.

 

 With this said, you should also do yourself a very big favour and buy some decent speaker cable and I highly recommend  you get in touch with @Bill125812 who can discuss your needs and offer you a very high quality and affordable solution.

 

Good luck with it and please keep in touch and let us know how you get on

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47 minutes ago, Pukara said:

Hey Andy,

 

The speaker wire used was from Bunnings    - Studio Accoustic  16GA 

 

Aah, OK ... I notice the reel is 30m long - I presume you did cut off 2 pieces at 4 to 5m, Justine?

 

This Bunnings cable has the 2 conductors right next to each other ('figure of eight' cable).  This means ... low inductance and high capacitance - the exact opposite of what (earlier, anyway) Naim amps liked.

 

You could do an experiment ... grab hold of the 2 conductors and pull them apart so they are no longer joined (or use a Stanley knife to cut the join between the 2 conductors, if the cable doesn't let you pull it apart).

 

Then try to separate the 2 strands by 10-20mm, along their whole length ... to mimic Naim spkr cable.  Then switch on the amp - and play it for a few hours at the same level you were playing it, the other day.  Either:

  1. It will still get hot - in which case the cable is not the problem ... the amp can't cope with the low impedance of the spkrs (and shouldn't have been sold together).  The dealer needs to change the amp for you.
  2. Or it won't get hot - in which case, the cable is the culprit.  You then have 2 choices:

a. buy some (hideously over-priced!) Naim cable!  :lol:

b. or follow rantan's advice and get Bill to make you up some cables.  But you need to tell him these, unfortunately, need to be:

  • high inductance, and
  • low capacitance.

(This is the opposite of what a good spkr cable should be!  :( )

 

 

Good luck!  :thumb:

Andy

 

Edited by andyr
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Ok thank you, I will let you know how it all goes. I really appreciate the help from you all.........

Cheers

Justine

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My two best suggestions are:

1. return the Naim to the dealer for refund and buy a well designed amplifier that can operate successfully with any half decent speaker cable. If you want a one box solution try a Cambridge CXA 81 and keep the  $2.5 K difference for anything you want.

2. Burn the cable you bought from Bunnings or give it to the salvos for their  op shop.

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I owned a Naim unity Star.   I ran quite a few speaker cables from it. Many were 5m in length. It ran all day.  Never had an issue.  The Star does have a bit more grunt,   I would recommend a nice thick Speaker Cable like Canare 4s11.  Certainly get rid of that crap from Bunnings.  The Naim all in one boxes are extremely good, and has that Naim sound.  Very refined.   

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12 hours ago, Pukara said:

Hey Andy,

 

The speaker wire used was from Bunnings    - Studio Accoustic  16GA 

 

C6840356-80B3-4EBC-AC14-C8ECA9C0559C.jpeg

According to speaker wire gauge charts like the one below 4-5m length 16 awg Bunnings cable on 3 ohm speaker load is borderline but it is usually not the cause of an amp overheating, nevertheless take it back to the shop and ask. Also, check that left and right cables were connected properly like -/+ve same on both sides, no wire filament loose ends touching the -/+ve ends of the cable or amp connectors.

BFA9E6EB-EDFB-476A-9377-A35085BC793B.png

Edited by Al.M
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How were you playing music? If you were using Airplay or Chromecast make sure the volume is turned right up on your phone/tablet. If no the Atom will have to work hard to compensate. Use internet radio to give you an idea of what the volume should be set at when using the phone etc

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On 29/01/2021 at 10:22 AM, CD Boy said:

How were you playing music? If you were using Airplay or Chromecast make sure the volume is turned right up on your phone/tablet. If no the Atom will have to work hard to compensate. Use internet radio to give you an idea of what the volume should be set at when using the phone etc

 

Sorry, CDB - I'm rather confused here.  :(

 

How does the Atom have to "work harder" if the input music signal is turned down ... compared to when the input music signal is turned up?

 

Thanks,

Andy

 

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Use Naim able with the amp , most amps it doesn't matter what speaker cable you use ,with Naim it does as the amps can got into oscillation and get hot if you are unlucky.

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2 hours ago, andyr said:

 

Sorry, CDB - I'm rather confused here.  :(

 

How does the Atom have to "work harder" if the input music signal is turned down ... compared to when the input music signal is turned up?

 

Thanks,

Andy

 

He's talking about the input signal level. If the level coming in through the input is very low then the volume on the amp would have to be higher than normal to achieve the usual volume level output at the speakers. 

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1 hour ago, btiltman said:

He's talking about the input signal level. If the level coming in through the input is very low then the volume on the amp would have to be higher than normal to achieve the usual volume level output at the speakers. 

 

That's what I assumed.  :thumb:

 

But it's the output level of the amp (ie. the power it's outputting) that determines the sound level of the speakers.  IOW, the sound level from the speakers is related to the watts that the amp is putting out; this (spkr) sound level is what determines how hard the amp is "working"!

 

So it's irrelevant whether:

  • the input level to the amp is low ... so the volume control is turned up high
  • or the input level is high ... so the volume control is only turned up a little bit.

Andy

 

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Try your Atom on internet radio or Tidal etc. See what volume you are using on the Atom. If and when you are using a bluetooth or airplay device adjust the output volume on the device (phone etc) so that the Atom volume is then similar to the internet radio etc signal. If the Atom gives the over heating warning when used like this then I would talk to your dealer. This is not normal.

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