NAIM Audio NAC 82 (NAC82) - looking for Service Manual or Schematic

[tiefbassuebertr]

A friend of me want to replace the electrolytic capacitors.
there are three variants (go to the attached images) :

1) Tantal (blue radial version) according post #12 (14) good replacement is KEMET's axial type T110 - go to
https://content.kemet.com/datasheets/KEM_T2031_T110_AXIAL_T212.pdf
2) usual electrolytics, axial, blue version (maybe BC components or Philips, probably for the mute control unit)
3) yellow axial version from S.L.C.E. - go to
https://aeservice.fr/en/product/slce/

The question rises up, which of the capacitors are critical regarding reliability and sonic performance.
If there was a circuit diagram it would of course be easy to find out.
Maybe one of the member can upload this - thank you very much in advance.

This URL's don't provide the wanted information:
https://skyfiaudio.com/products/naim-nac-82-nac82-rare-olive-style-preamplifier-naim-hi-cap-hicap
https://community.naimaudio.com/t/olive-nac82-no-serial-number-staff-build/30972/2
https://www.dastereo.ru/t/prodam-naim-nac-82-oficzialnyj-polnyj-servis/36228
https://www.ebay.de/itm/256485493815

P.S.: special parts from front PCB of control unit (go to sixth attached image and the last both images in post #13):
1) TC4514BP
https://pdf1.alldatasheet.com/datasheet-pdf/view/114285/ETC1/TC4514BP.html
Short form data in service manual of SANSUI's A-1500R (integrated amplifier)
https://audiocircuit.dk/downloads/sansui/Sansui-A1500R-int-sm.pdf
2) MCU: unknown due to being covered with a sticker with the Naim Audio logo. Program Date: 31-1-95

 

[tiefbassuebertr]

additional attachments

 

[jpk73]

What a beauty! Replace all lytics and tants if this was never done. Nichicon UKZ, UKW, UFG etc. are fine (low ESR caps are not recommended). Kemet T356 or TAP series by AVX are good replacements for the tants. No schematic is needed for recap, just keep track of polarity and replace like for like. You can find tons of info on pinkfishmedia.net about recapping a NAC82.

Generally there are supply rail caps, caps around regulators and caps in the buffer and gain stages. In and out caps are usually tants, the golden ones are often decoupling and feedback, but the exact information you can look up by googling schematics for NA729 and NA321. These are the circuit used in most Naim preamps. Phono cards are NA522 or NA523. Some people keep the brown ROE caps if they are still fine, but I would replace them all.

 

[rayma]

A low cost commercial unit, such as this, only has critically necessary parts.
Of course, some of them may need to have low ESR and high ripple current.

 

[tiefbassuebertr]

under
https://community.naimaudio.com/t/olive-nac82-no-serial-number-staff-build/30972
are to find images of a device with various modifications (manly replacing and adding elcaps), and one of the members are thinking about undoing the modifications to return to the genuine condition.
A closer look to the attached images (from the above mentioned URL) shows that the blue tantalum balls have been replaced by the smallest available WIMA MKS versions for 10uF (the capacitors that are in the signal path - I did that 30 years ago in my NAC 42 pre-amplifier, but with 2.2uF Siemens MKH versions, since that was the best compromise between smallest available size at those days and a still acceptable higher f3; nevertheless the sonic performance was better in all respects, especially in the upper frequency range, i.e. less aggressiveness and sharpness).

Additional I note, that the yellow axial Sic-Safco elcaps were not removed, but were moved to the underside (solder side) of the main PCB - go to image No 4.

What is also noticeable is that the blue axial types from Philips or BC components were not removed and replaced.
Maybe it is possible that these capacitors (on each reed relais "LITTELFUSE/HAMLIN HE721A0510") are those that have the task of ensuring that no pop noise occur during switching when selecting the input source (parts of a mute control unit), so that it is not necessary to turn down the volume control knob before switching on source select.

Really no schematic available of this more than 30 years old pre-amp device ?
What about the availability of the programmed EPROM from image No 6 from post #1 ?

P.S.: Why prefer Naim Audio tantalum elcaps instead foil versions in the signal pad ?
What means the term "Staff Build" ? Maybe a brand name ?

 

[lohk]

I also did once replace the tantalum capacitors in a NAC42 with Wima MKH caps. I hated the sound immediately and changed it back again. BTW: most Naim schematics from those days are basically the same, at least for the signal path.

 

[tiefbassuebertr]

What a beauty! Replace all lytics and tants if this was never done. Nichicon UKZ, UKW, UFG etc. are fine (low ESR caps are not recommended). Kemet T356 or TAP series by AVX are good replacements for the tants. No schematic is needed for recap, just keep track of polarity and replace like for like. You can find tons of info on pinkfishmedia.net about recapping a NAC82.

Generally there are supply rail caps, caps around regulators and caps in the buffer and gain stages. In and out caps are usually tants, the golden ones are often decoupling and feedback, but the exact information you can look up by googling schematics for NA729 and NA321. These are the circuit used in most Naim preamps. Phono cards are NA522 or NA523. Some people keep the brown ROE caps if they are still fine, but I would replace them all.

Yes - according the attached circuit diagrams there are - except the tantalum caps in the signal pad - only one cap in the NFB pad, one cap behind the resistor in the positive rail (actually part of power supply) and one cap on the module for the mute control unit.
But still, a circuit diagram or, better yet, a proper service manual (and possibly service bulletins published later) for exactly this model would be helpful, as one can see numerous differences in detail between the circuit diagrams shown in the attached files.

 

[jpk73]

I should have said low ESR electrolytics are not recommended in the signal path of a typical Naim circuit. The schematics you can find easily with the numbers I mentioned. Wimas in place of the tants will change the typical Naim sound not necessarily for the better - read up on this in the green forum. I would keep it as original as possible.

EDIT: you already found most of the schematics, great. The NA729 would be helpful too. Naim service manuals are normally not available on the net with very few exceptions.

 

[tiefbassuebertr]

I also did once replace the tantalum capacitors in a NAC42 with Wima MKH caps. I hated the sound immediately and changed it back again. BTW: most Naim schematics from those days are basically the same, at least for the signal path.

In what way the sound deteriorates in order to come to this decision ?
Siemens MKH wasn't best choice, unfortunately for WIMA MKP space is an issue, but sonic performance is even better than at MKH (actually MKT).
The first attachment show the versions, what I have choice for replace at those days on my own NAC42 device and second the version, which I prefer in terms of sound.

 

[Weaverish]

"What means the term "Staff Build" ? Maybe a brand name ?"

It was built by a Naim employee for their own use, this was allowed under strict criteria, modification from standard build was not allowed, but people did it anyway. I certainly did and nearly got sacked for it.

 

[tiefbassuebertr]

Thank you very much for clarify.
Since you work or have worked for Naim Audio, you probably know why Naim Audio used to prefer tantalum capacitors in the signal path and still do today.

On the one hand, it is the case that the capacitor is biased due to the asymmetrical (single) supply voltage of the gain stages (in contrast to most other devices with a symmetrical (±) supply voltage), which makes the use of elcaps less problematic - but OTOH I have nevertheless noticed, that this is in contrast to both normal ones of aluminum Elcaps as well as foil versions tend to sound harsh.

 

[lohk]

In what way the sound deteriorates in order to come to this decision ?
Siemens MKH wasn't best choice, unfortunately for WIMA MKP space is an issue, but sonic performance is even better than at MKH (actually MKT).
The first attachment show the versions, what I have choice for replace at those days on my own NAC42 device and second the version, which I prefer in terms of sound.

Of course it was not the best choice, but - as you said - the MKPs were too big for the pcb. I did not like the sound, which was hard, somehow distorted and not musical at all. The smoothest sound I could get with the old Naim circuits (actually a NAC42, converted to a NAC42-5) was using wet tantalums (KEMET T110) for the signal caps.
In my experience polarized electrolytic caps will sound at least ok or sometimes even extraordinary good if properly biased with DC. This seems to be in contrary to the usual belief.

 

[tiefbassuebertr]

supplement to post #1 - additional images of various parts in higher resolution (from the device of my friend):

 

[tiefbassuebertr]

Of course it was not the best choice, but - as you said - the MKPs were too big for the pcb. I did not like the sound, which was hard, somehow distorted and not musical at all. The smoothest sound I could get with the old Naim circuits (actually a NAC42, converted to a NAC42-5) was using wet tantalums (KEMET T110) for the signal caps.
In my experience polarized electrolytic caps will sound at least ok or sometimes even extraordinary good if properly biased with DC. This seems to be in contrary to the usual belief.

interesting advice despite the costs for it - this version I had never tested:
https://content.kemet.com/datasheets/KEM_T2031_T110_AXIAL_T212.pdf
https://www.mouser.de/ProductDetail/KEMET/T110C106K050AT?qs=9XoaYFg1weLBdGL0IO5jKg==
It's definitely worth giving this one a try for sound check in this (and other) amp models from Naim Audio.
The usual assumption that film capacitors are better in the signal path is certainly due to the fact that all comparisons that I know of have taken place under unbiased conditions, because there are only very few brands and amp components like those from Naim Audio, Nytech, etc. that are operated with a single supply voltage - check out also
https://www.diyaudio.com/community/threads/output-capacitor-subjective-and-objective-views.167580
https://www.diyaudio.com/community/...-with-ac-speaker-output-not-dc-wanted.216996/
P.S.: Mr. Gerhard Haas from Germany (experience electronics) is even convinced that better sound results can be achieved with biased Elcaps than with biased film capacitors. He is the author of the "BLACK DEVIL" amp diy project from German's magazine ELRAD - go to post #39 under
https://www.diyaudio.com/community/threads/your-opinion-about-this-schematics.154493/page-2
But exact comparison results under biased conditions between both kinds of capacitors I have never see until today.

 

[limono]

Better is always the enemy of good. Keep this in mind. If you don't buy for the casework like myself but for the Naim sound , it makes no sense to make it Non- Naim especially if you're not considering keeping it forever. There is no market for modified Naim kit beyond DIY circle which knows better anyway . Opposite, the following is so fierce that if Naim authorized center is not doing the re-cap it may sell better with old caps. With pieces like NAC82 which were a step below the top of the line it's not a small consideration.

 

[tiefbassuebertr]

I agree. This is generally an important fact today (because really good sound has become much less important today than the existing original condition when selecting vintage devices in used condition).
But this is especially true for audio devices, whose brand name stands for a specific sonic character (Naim Audio, Pass Labs, McIntosh, Burmester etc.).
Except, when modifications are performed in companies like those under
https://swobodaaudio.de
or in the manufacturing company itself.

 

[Weaverish]

Thank you very much for clarify.
Since you work or have worked for Naim Audio, you probably know why Naim Audio used to prefer tantalum capacitors in the signal path and still do today.

On the one hand, it is the case that the capacitor is biased due to the asymmetrical (single) supply voltage of the gain stages (in contrast to most other devices with a symmetrical (±) supply voltage), which makes the use of elcaps less problematic - but OTOH I have nevertheless noticed, that this is in contrast to both normal ones of aluminum Elcaps as well as foil versions tend to sound harsh.

Use of tantalum is definitely part of the Naim sound, they even use them in the Statement system. Foil has a more analytical sound, so they can expose weaknesses at other points in the chain

 

[tiefbassuebertr]

This is correct. But the proposal, using of Kemet's T110 electrolytics as replacement made the owner of this preamp curious.
Do you know the brand name from the original ones used (blue ball tantalum ellectrolytics) ?

 

[limono]

They were either NEC or Panasonic. I have 10uF and 100uf /6V SMD capacitors in coupling positions in Supernait 1. Interesting thing is the following Supernait 2 and 3 replaced SMD caps with beaded through hole Tantalums , also they replaced SMD resistors with through hole parts in signal path. I guess old parts sound better.

 

[jpk73]

The blue beads were NEC as far as I know, but they also used red ones and yellow ones etc. in earlier products...

Does Supernait 2/3 sound better than v1?