Naim Nac 42.5 Naim NAC 42.5 servicing?

[John_73]

Hi folks.

Bought a Nac 42.5 rather cheaply this week (cheap due to it being minus the outer case, and I’ve fortunately had a spare in storage). I just need to give the outer case a fresh coat of satin black paint, and neatly linish the front edges.

My 42.5 uses the ROE bi-polar 47uF 40V psu decoupling caps. Is there any reason why I cannot use Panasonic FCs in these positions? I know it means replacing axial with radial, but as this 42.5 wasn’t in 100% showroom condition, not too concerned about maintaining the axial cap originality. Was a tad concerned incase the ESR of the FC would be too low for these positions? The 24V supply for the NAC comes from a mint condition CB NAP160, serviced by Class A in 2022, which I also got this week. Delighted/somewhat gob-smacked by it!

I also have some spare 47uF 63V axial Vishay 031 AS that I could use instead of the FCs. Which would be best for psu decoupling in the 42.5?

As for the feedback caps, I’ll be using NOS ROE maroons. I just love their signature, and unlike many others, was never happy with the Nichicon KZs as replacements. I haven’t tried the Fine Golds (yet), or the Naim approved Samwha SGs however.

For tants I’m using new AVX stock.

To be honest, the untouched 42.5 sounds bloomin’ superb as-is. Really REALLY been enjoying it with no sign of any typical ‘tired’ cap nasties with the sound. But I know that as the caps in the pre are 37 years old the electrolytics are likely on borrowed time by now, plus the selector and monitor/mute switches need replacing (have bought like for like replacements already) so I might as well do the caps too when I have it apart.

John.

 

[OzBrit Audio]

You might want to have a look at the Avondale gyrators on the Avondale web site if you're doing an overhaul. These apparently provide a good lift in the imaging and detail capability of NAC without changing the overall presentation. You simply take out the 27R resistors and replace with the gyrator PCB - looks pretty straightforward to me.

Haven't tried them myself yet but like you I have a 42.5 sitting in a box waiting to be powered up. Cosmetically it's pretty much perfect but I don't know how it sounds. I am still waiting to get my 24V supplies setup before I can even try it out. Avondale have a shunt supply board which is claimed to be the 'dogs' when it comes to NAC pre amps so I intend to invest in one of those.

Good to hear you think these boxes sound so good. Are you using the phono stage or line input for your listening?

 

[hp1]

The 160 powers a naim preamp really nicely and is a very good power amp . I think the 42.5 has the modded buffer input circuit which tightens up the bass over a 42, might be worth a check though.
why not buy a peak atlas esr70 as the caps could well be ok , then you would know.

 

[laverda]

You can take the NAC42 and .5 / 62 / 72 /102 to another sonic level with just a few cost effective mods...by replacing the 27r resistor with a up to date AA Gyrator / Reg is a must. Last year we spent months trying to make the 102 sound good with an arsenal of mods and upgrades....and a 6 x reg PSU, alas we gave up, on later investigation and advice recieved it needs a new earthing |(0v) solution.

One of my first DIY projects over 25 years ago and couldn't believe the improvement. With further carful selected component swap outs further improvements were attained.

Then the power supply or rather the quality and No of power supply rails.

Below is a humble NAC62 of many years vintage. With all the MODs and upgrades possible I think. At the time it blew away the latest Naim NAC52 and PSU. The owner of the 52 was gob smacked as I recall.....

 

[Avon]

I don’t recommend you change the ROE capacitors as you will change the sound. As they’re sealed, there’s little opportunity for their electrolyte to leak, unless you crack the bottom seal during removal. They’re a definitive part of the Naim sound in my opinion.

I agree with the gyrator mod BTW.

 

[John_73]

Thanks for the suggestions everyone. At present, I want to keep it stock, at least as far as the original circuit is concerned, though the Avondale gyrators sound like something I may well give a try at a later date. Not looking to do any hard-core modding at present.

Yes, fully intend to stick witn the ROE in feedback positions, though will use NOS there. Ditto tants on a like for like basis, using AVX.

I really just needed to know, going back to my original post, whether it’s OK to use Panasonic FCs for the psu decoupling cap positions, or whether their lower ESR would cause issues? If so I have Vishay MAL203138479E3 which are axials I could use as an alternative.

 

[Avon]

The PSU de-couplers follow a 27R resistor, so their ESR will be swamped by that.

I don’t see the point of using NOS feedback capacitors (of uncertain providence), as they’re are in series with a 1k resistor.

 

[John_73]

The PSU de-couplers follow a 27R resistor, so their ESR will be swamped by that.

I don’t see the point of using NOS feedback capacitors (of uncertain providence), as they’re are in series with a 1k resistor.

Thanks Avon.

 

[charly63]

Below is a humble NAC62 of many years vintage. With all the MODs and upgrades possible I think. At the time it blew away the latest Naim NAC52 and PSU. The owner of the 52 was gob smacked as I recall.....

hello all,
Sorry Mr Laverda but your pic was a NAC-42 not a 62.
And for a NAC-72 , i think you cannot install AA Gyrator / Reg.

Regards

 

[Avon]

hello all,
Sorry Mr Laverda but your pic was a NAC-42 not a 62.
And for a NAC-72 , i think you cannot install AA Gyrator / Reg.

Regards

I have them in my NAC72, so I must have done something wrong.

Laverda's principle is the same, regardless of what the pre-amp is, so you're being finnicky.

 

[laverda]

hello all,
Sorry Mr Laverda but your pic was a NAC-42 not a 62.
And for a NAC-72 , i think you cannot install AA Gyrator / Reg.

Regards

LOL...it's no longer a 42.5 / 62 or what ever, the upgrades still apply.

 

[GordonM]

You can take the NAC42 and .5 / 62 / 72 /102 to another sonic level with just a few cost effective mods...by replacing the 27r resistor with a up to date AA Gyrator / Reg is a must. Last year we spent months trying to make the 102 sound good with an arsenal of mods and upgrades....and a 6 x reg PSU, alas we gave up, on later investigation and advice recieved it needs a new earthing |(0v) solution.

One of my first DIY projects over 25 years ago and couldn't believe the improvement. With further carful selected component swap outs further improvements were attained.

Then the power supply or rather the quality and No of power supply rails.

Below is a humble NAC62 of many years vintage. With all the MODs and upgrades possible I think. At the time it blew away the latest Naim NAC52 and PSU. The owner of the 52 was gob smacked as I recall.....

My 62 is powered from a HiCap with WitchHat Dragon Newt regulators and Avondale FWB2 rectifiers.

Would gyrators be any benefit on top of this already super quite power rails?

 

[nuit73]

Hello,
Is there a schematic or a detail photo to implement AA Gyrator on NAC 42.5 or 62?
Gyrator look very interesting

 

[MJS]

I've played with gyrators and stiffening the input voltage divider on the Naim preamp circuits. The 27R/47uF combo by far keeps the Naim signature in place but refinement can be had by a decent voltage divider arrangement. What JJ calls, I believe, the tranquility mod. I find gyrators give you transparency but also sterility to the sound.

 

[John_73]

When replacing the original Lorlin rotary source selector switch, should one go for the Make Before Break CK1042, or the Break Before Make CK1032? Cheers.

 

[PigletsDad]

Source selector should be break before make - you want a bit of silence between sources, not both playing at the same time.

 

[John_73]

Source selector should be break before make - you want a bit of silence between sources, not both playing at the same time.

Brilliant, I did order the right one then! Thanks

 

[Mynamemynaim]

A few years ago when I did my 72 mods (I'm still using and loving my 72) I found that the RSL boards made a big improvement...but the bigger step was made by fitting on board regs. I used ALWSR in my power supply (mod' hicap clone) and also in the 72 (other super regs and gyrators are available!)
The ALWSR made the biggest difference in sound quality (when also combined with an improved earthing system)
All the little shoebox amps can be made into giant killers without too much effort...in my case the giant it killed was my 252 / supercap ...stone dead

 

[GordonM]

A few years ago when I did my 72 mods (I'm still using and loving my 72) I found that the RSL boards made a big improvement...but the bigger step was made by fitting on board regs. I used ALWSR in my power supply (mod' hicap clone) and also in the 72 (other super regs and gyrators are available!)
The ALWSR made the biggest difference in sound quality (when also combined with an improved earthing system)
All the little shoebox amps can be made into giant killers without too much effort...in my case the giant it killed was my 252 / supercap ...stone dead

I've seen the ALWSR mentioned in a few threads but can't find a link to what it actually is. I'm assuming it's a super reg like Avondale TPR4. But then you mentioned other super regs and gyrators fitted inside the 72 so I'm now confused. Could you please elaborate a bit for the record. Thanks G

 

[Mynamemynaim]

If you search this site you will find information on the Andy Weekes super regulator
It's a diy voltage regulator (that can be adjusted for output voltage) and supplies "quiet" voltage for many purposes

Try this thread for further reading....

Help with Nac72 Regs wiring please

So I want to wire my ALWSRs in to my Naim 72 in a more permanent and neat way than I had them before (though I was happy with the previous sound improvement) I just want to run the 4 regs to the two gain and two time alignment boards (these are Ryan Sound Labs boards) Should I just remove the 4...

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