Another Green light blinks !


last week i turned ON my Naim nait 5i-2 after a hibernation period @ 6 months

Allowed it to breathe for 2 hours on no load and then played music

worked well upto now

Started playing music this evening and after about 3 hours the TUNER light blinked and i knew this was an Over Current indicator.

The amp case was warm but not Hot.

I am mystified as to why this could happen ?

I had this happening to my SN2 and i corrected the phono stage corner freq.

But this time - i am playing music ( thru a ifi inano DSD DAC with a volume pot ) and into the Naim Nait 5i-2

The DAC volume pot is turned up all the way

The Naim nait 5i-2 volume pot is at 10 o clock

i am puzzled…

any thoughts ??


mpw, I just couldn’t say what this might be. Have you checked all the usual things like speaker cable shorts etc… What are the speakers?

Make sure you are using the line out and not the headphone output - the volume control shouldn’t be needed on the DAC. If you output from a headphone out then the level may be just too high for the NAIT.

Also try switching between filters. I don’t know whether the DAC filters very high frequencies from DSD - if not this may be causing the amp distress.

Beyond that, it could be a good idea to contact Naim support.

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I am using the line out of the dac

It’s a head Amp + dac

There are no filters on this dac

It happened again

But doesn’t seem to happen when the volume pot on the day is reduced.

But when I do that then the Naim Nait 5i-2 volume gas to be turned up lots and the music loses some sparkle.

I thought the dac volume should be turned up fully.

Will the problem go away if I use a dac only without volume control ?


Hi mpw,

If the unit is showing no signs of overheating & you aren’t running some really odd cables, this fault is usually caused by a faulty protection opto-coupler (common to S/Nait & Nait5i*).

It’s a 16 pin IC that sits in the centre of the amp stage. Easier to replace in a N5i than SN2, but not for the faint hearted.

A competent dealer should be able to sort it for you.


Hi Neil

Thank you

I live in Mumbai, India and i seem to be quite far away from a Naim service center or even a dealer.

My unit is out of warranty too.


I will first try to reduce the volume pot on the pictured DAC to about 80% and see if the amp is happy for atleast 4 hours of playtime on the trot.

Its quite normal for me - 4 hours music time in the evenings and late nights.

If i have no success - i will take my amp to a friends place and ask him to use it for a week with his source and check for the same problem.

Only when i have positively isolated the problem to be the amp than i will look at a remedy inside the amplifier.

Thanks for your inputs

Much appreciated.

I shall keep this thread updated and hope to bring a happy closure.


I think i am in deeper waters…

this morning after 35 min of play the CD light blinks and the amp case is warm to touch…



Hi mpw,

Unfortunately, I would say that randomly showing over current then over temperature like that, definitely points towards a faulty opto-coupler.

I hope you are able to get it sorted out.

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HI Neil

Thank you

I have contacted Naim support and will wait for their advise on Monday - Tuesday maybe.

Mostly they will ask me to take it to a dealer.

Here in India - am not sure if Naim has a service center.

Just to cross check - i will be playing the amp in my friends home today.

If the opto coupler has to be changed - hope its a commonly available one and that i dont have to send the amp outside India

Thankfully my SN2 looks fine. The TUNER light blinking is gone after i changed the phono settings. Played 4 records yesterday on the trot.


Hi mpw,

I suspect your Nait will have a white protection opto-coupler fitted, if you need to source a replacement part outside of Naim"s dealership network, Naim are currently using a black component manufactured by Vishay (CNY74-4).

Best of luck with it.

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I sent the amp to a close friend

he is running it for 3 hours a day for the last 5 days with Amphion 410 speakers

No problem he says…

I really wonder what could have caused the TUNER light to blink on the Naim nait 5i-2

was it in some way related to the connection of the laptop to ifi Nano iDSD LE DAC to the amplifier ?

a dry solder inside the amp perhaps ?

the power cord perhaps - i have a 10 gauge one … ??


Check your cabling, particularly the speaker cabling. First is it suitable and next check for faults, stray strands. What’s your mains like?

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Speaker cables are Naim naca5 - length 3.4 meters pair

no stray stands i see but u think i may have to check any loose contacts here - the termination…

since i am not using and support under the amp to lift it off the rack surface - the naca5 bends i think near the termination

( see attached pic )

please comment

much appreciated


I would carefully unscrew the caps on the speaker connectors to check all is ok inside.

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Looks OK to me


Looks poor to me. I’m no whizz with the soldering iron but I’ve done mine and they look much better than that. The wires should sit inside the slot and solder flowed in.

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Can somebody put up a pic of what a good soldering should be like ?

I do have some Cardas solder wire with me

I can take to a local technician and get it soldered

will be helpful


I hope to add to the new forum FAQ this coming week, and part of that will address good soldering on speaker cables such as NACA5.

A couple of images of good soldering from the old forum, courtesy of Peter at Cymbiosis…

And a few examples of poor soldering…

NACA5_1_ NACA5_2_

The trick is to make a wooden buck from a plank of wood - just drill a pair of holes to mimic the speaker sockets, which will hold the plugs for you. Then cut the cable and form the ends with the help of some pliers to fit in the slot of the plug. Use some kind of brace or strap to hold the cable in place, allowing you freedom to solder without trying to hold things in place ta the same time. Use a high powered soldering iron and heat the plug. Once done allow to cool and then trim off the ends and anything will impair the free movement of the metal plug within the plastic housing.


Hi bob, I would say that even the soldering in that HiFi GEAR picture is below par. I have experimented myself over the years (mainly from running a active system) and was or have been amazed at how much the sound can change with a solder joint that isn’t ‘quite’ right. The top picture in Richard’s post is how it should be done. If I can’t get mine to a very similar quality as that, I simply start again until I do. It can or does take quite some practice. This may sound silly, but I have generally found that it will sound as good as it looks.

Ok I thought it looked quite neat I will delete it.

The main thing is that the wires are formed to fit in the slot and that the plugs are hot enough (100w iron) to allow the solder to flow into the slots rather than sit as “paste” on top. Using a wooden jig helps stop the heat conducting away.
Most people’s won’t be as neat as Peter’s but should be fine. :blush: