NAD 106 Preamp Restoration/Upgrade Project

[nicst]

The stock RIAA low-end cut-off capacitors were 2200µF/6.3V and these were replaced with Nichicon PW capacitors of the same capacity but with a higher voltage rating (16V). Whenever possible, it is best to avoid low voltage (e.g., 6.3V and 10V) rated capacitors as their performance and longevity are typically poorer than their higher voltage counterparts. I usually try to use capacitors rated at a minimum of 25V, but in this case there wasn't sufficient space on the board.

Hi again! I am copying your mods to my NAD 1000, which is very similar. I took your advice to replace the DC filtering/decoupling capacitors C205/C206 from 220µF/25V with 470µF/35V United Chemicon KZE. But in the NAD 1000 the C215/216 are 1000µF/35V (strangely, since both the wiring diagram and parts list say 6,3V). I have a pair of 1000µF/25V Nichicon PW in store that would fit. But in the NAD 106 you say they are 2200µF. Should I increase to 2200µF or do you think 1000µF is a better value for the NAD 1000?

 

[Leestereo]

Since the 1000uF capacitors are already on hand, I suggest that you use them. The C215/216 capacitors determine high-pass filter cut-off of the RIAA equalization and the 1000uF value provides a F3 of 0.7Hz (MM mode) and 12Hz (MC mode).

 

[nicst]

Many thanks, again, @Leestereo!

The stock capacitor which immediately follows the sealed ALPS volume control is a 470nF MKT (polyester) film. It would have been good to replace it with a polypropylene (or similar) type, but unfortunately one that has a 5mm lead pitch and would fit the allotted board space was not to be found. The use of a larger film capacitor and installing it off the board is not generally recommended since it may add noise to the signal (due to the long unshielded capacitor leads and the capacitor itself).

On the NAD 1000, the design around C303 is slightly different. There is one more cap here. C301 and C303 are both 0.1µF, and the parts list say "P.P.". I guess that means polypropylene, but as you wrote here, there might be a discrepancy between the list and the reality, and I can not find any information about what these on the pictures are. Question is if I should let them stay, or if I should replace them with the Panasonic ECWF 120nF/250V that I have in store?

 

[Leestereo]

...On the NAD 1000, the design around C303 is slightly different. There is one more cap here. C301 and C303 are both 0.1µF, and the parts list say "P.P.". I guess that means polypropylene, but as you wrote here, there might be a discrepancy between the list and the reality, and I can not find any information about what these on the pictures are...

Considering the late 80s manufacturing date of the NAD 1000, the 0.1uF film capacitors in your picture are very likely to be polyester film types. What is the lead spacing of board for C301 and C303, 10mm?

 

[nicst]

Considering the late 80s manufacturing date of the NAD 1000, the 0.1uF film capacitors in your picture are very likely to be polyester film types. What is the lead spacing of board for C301 and C303, 10mm?

The board lead spacing is 8mm. There is enough space to fit the Panasonic ECWF 120nF. Its lead spacing is 10mm, but it has crimped leads that will help mount them on a reasonable distance from the board, I think.

 

[Leestereo]

If the Panasonic ECWF polypropylene capacitor fit, then it's an appropriate upgrade to the polyester ones.

 

[EC1]

@Leestereo, any idea that proton 1100 related to any NAD preamp? Any suggestions? Thx.
https://audiokarma.org/forums/index.php?threads/proton-p-1100-recap-upgrade.1022902/

 

[tanelpld]

Happy new year! Such a great thread!

Must say, it's a great preamp and what a breeze to work on. Got the unit untouched.
It really sounded under the blanket, no soundstage and not very exciting at all. There was some little noise in there and a bit more noise with the tone circuit on. Still a lot, lot less compared to some integrated vintages I have. So I used it for a week before getting to it. Sound even felt to the point of distorted sometimes.

Anyway - now have done the PSU lytes and couple in preamp circuit, cleaned the tone pots and connections.
What a transformation! It sounds great and dead quiet. It really came to life. I like the sound: BabyFace PRO -> NAD 106 -> Pioneer M-10X -> Beovox S45-2.
Thought I list the replacement caps used if anybody is interested:

PSU

• 2 x 2700/50 - Rubycon ZLJ
• 4 x 470/50 - Chemi-Con KY
• 2 x 47/80 - Panasonic FS-A
• 1 x 10/50 - Panasonic FR-A
• 1 x 47/50 - Rubycon ZLJ

Preamp

• 2 x 47/50 - Rubycon ZLJ as C313 and C314
• C317, C323 - TODO

Now I have a question. Being a complete hobbyist with no engineering background I'm not completely reading the schematics.
I would like to understand the function of each preamp circuit electrolytic cap? Anybody care to help?

C313 - Feedback‑to‑ground? So in that case audio grade caps are no use?
C317, C323 - ?

Left the phono and headphone circuit untouched for now as not using em.

 

[leesonic]

Now I have a question. Being a complete hobbyist with no engineering background I'm not completely reading the schematics.
I would like to understand the function of each preamp circuit electrolytic cap? Anybody care to help?

C313 - Feedback‑to‑ground? So in that case audio grade caps are no use?
C317, C323 - ?

Left the phono and headphone circuit untouched for now as not using em.

C323 is definitely in the signal path, it's the way the signal goes if you bypass the tone controls. Likewise C313 and C317 are when you ARE using the tone controls. Assuming I'm looking at the switch position correctly. It's early, and I haven't had any tea yet...

As to what caps to use, that's a question as old as time. Personally, I would use low-leakage in these places, because that is the way Pioneer, Sansui, Kenwood would do it. But because this is a higher level stage (meaning voltage or signal levels, not physically), some people might use something fancy like a Nichicon ES, KW, KZ etc.

 

[tanelpld]

Ah Thanks leesonic, low leakage makes sense, it states L.L. for these caps in manual, that supposed to be Low Leakage I guess?
But then what's low leakage, Nichicon UKL is 5 times lower leakage thank KZ for example. But UKL is pretty much the only one in this class, maybe couple more, and hard to source the values.
Anyway I tried couple of options, just with what I had laying around: Frolyt ERF on 47/25 and Panasonic FC on 100/25, sounded dull even compared to my NAD 114 that ran original caps in it still. With all Nichicon Fine Gold, sounds nice now. I did order some UKLs, maybe I give it a try just to see is there notable difference.

 

[Leestereo]

All original thread pictures restored (without Photobucket censorship).

 

[PabloTincho]

All original thread pictures restored (without Photobucket censorship).

Is Nad 114 the same as the 106 but not xlr ?

https://audiocircuit.dk/downloads/nad/NAD-114-pre-sm.pdf

 

[Leestereo]

Is Nad 114 the same as the 106 but not xlr ?

https://audiocircuit.dk/downloads/nad/NAD-114-pre-sm.pdf

From the schematic, the 114 is very similar to the 106. The main differences are found in the power supply circuits: whereas the 106 PS is fully discrete, the 114 uses ICs.

 

[PabloTincho]

From the schematic, the 114 is very similar to the 106. The main differences are found in the power supply circuits: whereas the 106 PS is fully discrete, the 114 uses ICs.

Is the Nad 1300 better than the 106 ?