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Naim NAIT 2 Restoration Project

Jo Sharp

Jo Sharp

Pulls on doors marked push
I've managed to buy an Olive NAIT 2 in good condition as a Lock-Down project. It seems to be in good order and when powered up does not make any unpleasant noises - no scratchy volume or balance pots.
DC readings on the speaker sockets are both under 6mV. Plays music with no nasty sounds, so I think I have a good starting point!

All caps seem to be original factory fit (Elna 6800uF power caps without date codes - ROE purple caps in Pre-amp section etc) so no recap since built in approx 1990. Holden and Fisher Transformer. Inspection sticker initialled by JLC.

Here are some thoughts on what work I'm planning:

1. The mains plug earth connects to the 0V signal line - so when using a Naim CD player I'll get an earth loop. Will therefore disconnect the NAIT mains earth line at the plug.

2. Can't find Elna 6800 caps online - replace with Kemet 6800s or Vishay 10,000uFs?

3. Roederstein 47uF in pre-amp - can use some NOS ROEs or Nichicon Muse. Are the NOS going to be as good as the Muses? Take the feedback caps 0V line back to main star 0V point.

4. The various 10uF alu electrolytics can be replaced with Rubycons (50V) and Elnas (35V). Or use film caps for the Input/Output DC blocking?

5. Thinking of fitting Gyrators on the pre-amp supply lines in place of the 27R filter resistor. Probably not enough power rail voltage to allow a 317 type reg.

6. Thinking of doing the pre-amp power rail mods - which resistors to split and what value caps to add?

looking forward to comments and suggestions from the DIY gang.
 
....and since I'm never going to use the Phono input, I can just disconnect this section from the power rails and leave alone....
 
It will have a single LM317 for the 24V, you can add more, one for each stage would be good.

Pete
 
For the reservoir capacitors, I would go with the Kemet 6800 uf as this is quite enough capacitance for this amplifier. Also, Naim usually put the right size of capacitors so there’s no major benefits to replace with bigger ones. The trick is to have the ESR as low as possible.
For the 47uf, I had good results with the Elna Silmic 2 on these little amps and the Nap 110, Nichicon Muse would be my second favorite.
For the 10 uf, I still prefer the Elna Silmic 2 but Nichicon Muse would be more transparent and natural.
 
Interesting Pete, there's no 317 that I can find...there’s just the large 2700uF axial cap on the pre-amp rectifier diodes output which feeds both channels.
 
Thanks for the Silmic 2 suggestion...I have lots of these left over from my Starfish and NAC 62 cap swapping days. Back then I found them to be rather soft/soggy and didn’t keep them. But I could try again.
 
Yes it would! If there’s enough voltage headroom....but if Martin managed then I’m sure it would be OK. I have several of Andy’s little gems in my parts box.
 
Hi Jo, I did not realise the Nait 2 mains earth connected to the Ov signal line; I use a Naim DAC with my Nait2 (second set up), so should I set the rear chassis switch to floating from grounded ?

Thanks Devraj
 
Hi Devraj,

I’d check with a voltmeter first to see if your Nait is wired the same way, as it is really important for safety to have one earth connection! But if the meter on continuity test setting shows a connection between the plug earth pin and a speaker negative socket, then you can switch the DAC to floating.
 
There's a tiny LM317Z next to the pre-amp cap. A straight swap for a 317T is a big win. Don't disconnect the earth at the plug, it's there for a reason. If you don't need the phono earth then you can disconnect it at the side of the PCB, or just put a 100R in series.
 
Another huge win - if you find it has too much gain then snip the 1k resistor in line with the 47uF feedback cap in the preamp. The gain stage is now a buffer instead and can use far more of the not-very-well-tracking volume pot.
 
^ That is big win; reduces distortion of amp overall, too - if you don't want or need the excess gain. Tastes vary of course.

@nobeone - you have a long memory!
I'll dig out mine this weekend and see how the ALWSR was set-up - I did it because I found I could, not because it was necessarily a good idea (or even much of a benefit) - about 16yrs ago ...
 
Mark,

That is great info thanks. I found the 317...I had stupidly assumed it was a transistor in the relay circuit whilst looking for a ‘normal’ size 317 reg (Peter, apologies). I’m a bit confused about the earthing arrangement though, and why Naim created the possibility of an earth loop via a CD player.
 
I think that might be because the Nait was designed before Naim made a CD player; and subsequently re-defined such as the 'Mains Earth-signal 0v link ' of the Naim sistem.
 
Worth replacing the tants too ... not sure that has been mentioned?

Jo would be great to have a list of what and from where for a basic service when you get round to it. Something for the reference section even?
 
Jo Sharp said:
Thanks for the Silmic 2 suggestion...I have lots of these left over from my Starfish and NAC 62 cap swapping days. Back then I found them to be rather soft/soggy and didn’t keep them. But I could try again.
Click to expand...

If you find the Silmic too soft and the Nichicon Muse KZ too bright or thin, try the Nichicon KW.
 
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