NAD 3020A recap assessment

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#41
Just the eight discs highlighted in pink on the right hand side of the amp.
Also C426, the larger ceramic disc which sits between the two pink highlighted ceramic discs at the top of the photo.
 

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#42
NP0 and C0G capacitors are as good as each other. If you have NP0 identified by a black segment across the top leave them alone. It is pot luck if the actual values of the new lot is as close as those on your board, possibly selected by measuring, are to the values specified in the Service Manual. The 2990xxx numbers are C0G. Presumably the last item on the list is to used across some supply traces. Ceramic capacitors are better than bulk foil for stabilizing circuits by that means.
 
#46
cb1 said:
Thanks mjona.
The new parts have been ordered based on the writing on the original ceramic caps, the service manual wasn't referenced.
Happy with that last item on the list being used in this location C426?
Click to expand...

C426 decouples the supply to earth. It will do that up into the r.f. spectrum. If you look up op.amp application notes you will see that ceramic capacitors are specified to ensure stability. The same applies for discrete component design. There is no need to change it.
 
#47
Have purchased the MLCC replacements and now wish to also try a Mylar capacitor replacement.
I want to replace two pairs of the green ones with polypropylene caps for the phono path but need to know what values to order. The marking on the sides are:
00752J 50VF
.027J 50VF
Does anyone know what values these are and what I should be specifying for the order, ideally from
https://uk.farnell.com/
 
#49
Hi,
Does such spray work with carbon pist pots ?

I also remember that all the switchs were not on the highest quality, on part with the amp price. It was an issue in a close design I refurbished (Proton AM20)

Is it not nicer to find some Styrenes vs the MLCC ?

And why not tstay for the green Mylars ? Does your LP and cartbridge are sota than they need a KP VS a MKT ? And all those straps onthe signal with aluminium wires, bouh !


Imho all those changes are not worthing the effort and monney spent. Better to find a little good phono pcbs as sugested and populate it with premium parts, transistors and passive parts.


On the other side there was certainly something to to do with the main amp caps... I would suggest a cheap but better volume pot though. people here or in the analog section can advice for some very good and very cheap.


lok what I found for free in a garbadge : perfectly working : Le Pionner SA 506 est un ampli au look et a la musicalite typique des 70's.
 
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#51
to what ? The C0G you listed are better and more reliable than Class 2 old disc if it's the answer you are looking for. Leave the green in place, they are nice.
Change the pot : great improvment for few bucks.


Sorry I can't help more here, I could have help on the main caps circuitry but it's already new and you had good inputs on that above I believe 🙂. The lytics of the phono stage need to be new if not already made as you did elsewhere.

I'm questioning myself about refurbishing the amp I linked cause sometimes it just doesn't worth the effort if it's not your everyday amp. The little Nad though is nice with loudpseakers with not too low impedance curve or low efficienty. Caps though make difference sometimes. Worked well on some little Cabasse iirc. That's not what you dreamed about for a Kef 107 or 104 Refs. Way to rephrase it in relation to what the equipment you have; phono, cartbridge, etc ! Sometimes it doesn't seem to matter : Pioneer SA-506 (NEC B616A/D586A pair)
 
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#52
cb1 said:
... now wish to also try a Mylar capacitor replacement.
I want to replace two pairs of the green ones with polypropylene caps for the phono path but need to know what values to order. The marking on the sides are:
00752J 50VF
.027J 50VF
Does anyone know what values these are and what I should be specifying for the order, ideally from
https://uk.farnell.com/
Click to expand...
I'd anticipate 7.5nF and 27nF.
Perhaps just sort on lowest voltage rating and polypropylene, so 27nF 630V is lowest in stock. 7.5n has no stock so you likely need to parallel or series.
Do you have a cheap DMM that measures capacitance?
 
#55
... a good thing to learn more, and you never had to change all a circuit if you want to understand what are the change in sounding term. You have t understand if swapping te caps is more for your brain than your ears. For the safety of the device, they were not needed (not old enough), for the sound, well it depends !



Definitly a good idea here to compare R & L, the only problem I could see is diaphony, but it doesn't matter in that purpose !
 
#57
Definitely the cap swapping is partly about satisfying the brain.. but I immediately enjoyed a big improvement after both of my recap projects. (Yamaha CR1020, NAD 3020A even just the electrolytics stage sounds good already..)
 
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