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Modifying the Nait-2

JTC

JTC

PFM Villager...
Hi folks.

As a few of us here have had Naim kit modified, either DIY or via experienced bods like Les, and in light of some positive listening tests with a newly recapped and mains-optimised silver bumper Nait-2, I'm interested in what can be done to take it a bit further.

At the moment all of the rhythmic integrity and excitement factor is there, and (post recap & with good mains) there's a surprising articulation and detail, coupled with sufficient power to drive my speakers. All-in, then, a bit of a bargain for the estimated £250 I've spent on the amp plus the work done on it.

However, it could do with being a touch smoother, and a bit more even-handed - i.e. it can sound a wee bit vague in more complex music and tonally it could do with more colour. Picky, I know, but if a little breathing-upon can really let this baby sing, why not?

jtc
 
THe next step is to replace the voltage regulator to the preamp stage with something a little better.

There is an LM317 which supplies both channels and the phono boards, in a tiny T092 package (looks like a transistor). Replacing this with LT1086 or LM317T is a moderate improvement; replacement with one of Andy's superregs is quite a revelation...

If you are not going to use the phono input (or have a separate phono stage) lift the two 27ohm resistors that feed power to the phono stage onboard. It reduces demands on the regulator, and stops a certain level of grunge cross-pollinating.

Bear in mind none of this will transform the amp into something it cannot be; but the result really builds on the Naits strengths and fleshes out the rest.

M.
 
The volume pot also looked pretty cheap in the Nait 2. Maybe replace that with a better one?

I agree that Nait 2 had real strengths - especially in sounding very coherent and 'together' - but detail, transparency etc and smoothness and tonal colour weren't too hot, I thought.
 
Nait 2 had real strengths - especially in sounding very coherent and 'together' - but detail, transparency etc and smoothness and tonal colour weren't too hot, I thought.
Click to expand...

Agreed. Very coherent and together, with a homogenous sound which I think sets it on a different trajectory to most amps (which try to split the sound apart, often splitting up the musical message as well). Detail-wise, it's not that bad in my own experience - not as detailed as more expensive amps, but all the important stuff is definitely there. Smoothness seems to be a function of the quality of the mains - it's pretty even that way when you uprate fuses and run from a dedicated CU. Tonal colour is a bit limited, but again improves with the uprated fuses.

Which leaves me wondering just how much can be squeezed out of the little Nait...

jtc
 
I agree that Nait 2 had real strengths - but detail, transparency etc and smoothness and tonal colour weren't too hot, I thought
Click to expand...
I agree on the smoothness part here, but that's about it...
Imho transparency is very good, and detail even better.

I had a Nait-2 for about 4 years.
Last year I bought me a 72/180 combo. (swapped the 72 for a 102 this year)
The 102(or 72)/180 combo was a bit smoother, more dynamic and had better grip in the low-end, but...the Nait-2 was about 95% as open and detailed as the 102/180 combo.
(at a fraction of the cost)

I had my Nait-2 "recapped" by a guy called Louis Raatjes in Holland.
(kinda wellknown for his amp mods)
It sounded great.
(Allthough I couldn't tell much difference from before the recap)

I was told that the weak volumepot couldn't be swapped for a better one. (not enough space inside)

regards,
Alco
 
You can alway find a way to change the vol pot with a bit of thought.

you need to look at

rectifcation.....fast recv. schottky
vol pot..........stepped attn.
internal wiring..PTFE silver/agcu plated
opamps?
replace connections better than cleaning
there much more but thats half thefun doiinng the research.
 
Things I've tried: -

Better PSU - always works well with almost everything that's powered. The Nait is very simple compared to most, no input buffers and only the gain stage and the phono stage being powered from a regulated supply.

Disconnect the phono stage if not used, by lifting the 27R's that Martin mentions.

On the line level Naits Naim have used part of the phono to provide input buffering, but only to the phono sockets, AFAIK.

There's little current drain here, so an LM317T will make a subtle difference, some shunt regulation in the form of maybe TL431 + FET current source could work well, a really good regulated supply will work wonders.

Change the 47u rail decoupling caps for Oscons, these work wonders for the LM317 type supply.

Try Les's BC solid aluminium caps for the signal path 10u's (making sure you get them the right way round).

Change the gain stage 47u cap in the feedback path for Elna Silmic (don't increase the value).

Change the Tantalum cap in the power amp feedback path for Elna Silmic (don't increase the value).

Things I haven't tried, but are likely to be beneficial: -

Change the rectifiers for Schottky or better still, soft recovery diodes.

Change the volume pot for something better - I wonder if Les's recent recommendation (Omega?) would fit here?

A switched attenuator could be good too, but needs to be compact to fit, it would overcome the problem of channel balance at low levels that's common to almost all Naits.

New connectors all round.

Change the power amp feedback resistors for higher precision types.

Change the gain stage feedback resistors for higher precision types

There's no internal wiring or opamps to worry about.

Andy.
 
Thanks guys - loads of things to try. Maybe this will be my winter project, turning the Nait into a SuperNait :)

jtc
 
As reported elsewhere, I recently got meself a Nait 2.

After having tried it out in my main system and then going back to my normal amplification, 82/180 (but this time without a Hi) I also noticed (without having read this thread) that there was just a "togetherness" in the Nait that was now missing.

So, it uses fewer active stages than the separate amps. Maybe that what one hears. Not having a meter or two of Snaic between pre/power amp can't hurt either.

Some (quite wild) ideas on modification:

- Outboard power supply, a la Cyrus. But what part should one outboarding, pre or power amp? How is the standard pre amp power supply in the Nait, does it have it's own winding on the transformer?

Well then:

- Outboarding the pre amp supply: Could be a Hi Cap, nice and tidy via a connector in the unused hole that is there if one want to use the Nait as a pre only. But that's maybe a bit of an overkill. Some home cooking then.

- Outboarding the power amp supply: Could then be fully regulated via the classic Naim regulation boards (or a copy, probably). Bigger transformer. What type of output trannies are used in the Nait? Can they handle some more power? Fan cooling, NAP 135 style (it's starting to go out of hand now...)

- My guess is that it has a higher cut off for the high pass filter on the power amp vs my 180. Depending on the system around it, this could be lowered.

JohanR
 
Johan - some good ideas there I've toyed with doing myself, untill I realised I like having a one box amplifier, and not an underpowered NAC/NAP/*cap clone based around a Nait.

I'd just point out that bandwidth limiting can be a very good thing, especially in the context of an 18W amplifier. Changing component values* in order to extend the range of bass 'power' downward would probably be detrimental. The reason is simple - demanding more bass energy will cause greater demands on the amplifier voltage rails, increasing potential for intermod distortions. Subjectively, I think the lithe balance of the Nait would suffer.

Doing the preamp section voltage regulation properly will deal with many of your concerns...

Regards,
M.

* IIRC the coupling caps are 10uF, actually the Naim standard across equipment)
 
Johan - some good ideas there I've toyed with doing myself, untill I realised I like having a one box amplifier, and not an underpowered NAC/NAP/*cap clone based around a Nait.
Click to expand...

Yes, it's probably not worth doing. But always fun to dream away. Lazy as I am, I will probably not do anything anyway.

JohanR
 
Hi

My old NAIT2 is (like I said) old and needs recapping. OK, so I will replace those signal / decoupling capacitors with the ones mentioned here (thanks 4 da info). But what about the PSU smoothers (originally 2x Rubycon 6800uF and 1x ?? 3300uF)? What makes do you recommend here?

Plus, my NAIT needs new power-amp output transistors. Obviously, I can't source the original NA005's used in the NAIT, but I believe Naim recommend BD743 as a replacement. Any comments here?

Is there any source recommendation for the large resistors close to the output power transistors? And what make of resistor to replace the odd blown one on the board?

Comments more than appreciated, BobMax
 
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