Wanting to MOD/overhaul my NAD3130 - diyAudio
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Old 7th April 2013, 10:36 PM   #1
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Default Wanting to MOD/overhaul my NAD3130

Hi guys from a newbie.

I was hoping someone on here could possibly help with some advice and/or information on how i can best modify my 3130.

The main thing i want to do is see if i can upgrade the main to-3 transistors and if so ( i have a few candidates) do i need to alter any of the surrounding circuitry.

And also i plan to upgrade/ replace some or poss all the electrolytic caps.

One mod i would definitely like some info/assurance on is, i am led to believe from a source that i can double the capacitors Smoothing/psu section just before the bridge???
My amp currently has 2 6400uf 50v caps in it, i have seen a 3130 on ebay with 2 monster 10000uf caps on the chassis and an unknown voltage but they look large so prob more than 50v.

So could someone assure me if i can replace my 6400uf caps with 10000uf or higher?
And can i safely use higher voltage ones without the need for modyfying the rest of the circuit?
And finally i am also led to believe i can run a 2nd set of caps like those mentioned above in parallel with the 2 existing 6400uf caps.

Any help/light shedding on these many questions would be greatfully received.
PaulB
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Old 8th April 2013, 01:47 AM   #2
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Take it one step at a time would be my advice - power supply is definitely the first step. Don't just add extra microfarads willy-nilly, rather build a CLCLC filtered supply. Use lots of paralleled smaller valued caps rather than a few big ones because then you'll get lower ESR.

As another possibility, ditch the mains trafo entirely and get a couple of SMPSU bricks then filter them like crazy
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Old 8th April 2013, 02:46 AM   #3
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I read somewhere that the original 3020 had a "tuned" power supply. It seems that the designer carefully selected psu capacitance by ear. This is apparently a trick that many budget amplifier designers use. It is likely that your amp was designed the same way.

You can increase power supply capacitance but this is not guaranteed to make a better sounding amp.

I am with Abraxalito start with a CLC filter. Play around with Duncan Amps PSUD II to see the impact of your planned changes.
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Old 8th April 2013, 09:40 AM   #4
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Thanks for the replys guys,
I am going to keep this restoration/mod preety simple and nothing exotic.
I am not a massive audiophile i guess, as i actually like horrible things like tone controls :lol:

I def am going to be sticking to the original psu, at this point and most likely in the future i will be keeping the original tranny, as i think a torroidal will be too expensive.

Main thing will be caps, and drivers, then setting up the currents and voltages via the pots.

Thinking about swapping the drivers, for uprated components, but have also noticed through some reading that some people feel that the 2n3055 is a fairly sorted component.

Cheers
Paul B
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Old 8th April 2013, 10:13 AM   #5
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If you over value the main smoothing capacitors, you will cause severe strain on the mains transformer and rectifier. Why do you think the original values were chosen? it is a happy medium between the components used. Why change them, they are designed like that. The mains transformer will be less efficient as it has to charge the oversized capacitor
If you want to modify the sound, drivers, output transistors etc etc, why have a NAD.

Always replace the 2N3055/MJ2955 output transistors with Motorola manufactured components. They are filled with silicon grease and are better at dissipating heat and therefore more reliable.
Silicon Transistors, unlike Germanium have a good shelf life and do not decay. Don't change them if they are not faulty as they don't "wear out".
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Old 8th April 2013, 05:41 PM   #6
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One of my main reasons for wanting to upgrade the 2n3055's and the MJ2955 is that this amp was built and designed a long time ago, and doubtless to say that if NAD was building this amp now it may very well have used newer and better alternatives.

The transistors i have in mind have very similar spread sheet charecteristics, but are slightly beefed up.

The transistors i had in mind was MJ15003 + MJ15004 which i think should do the job nicely.

Also with regards to the caps I had this idea after reading up on some work done by Fidele audio on these amps and the 3020.

I am wondering if maybe mine has been modded already as i think the 2 smoothing caps were not originally 6800uf ?
but thats whats in.
Perhaps rather than putting much larger caps in i could go the Parralle cap route with smaller caps.
Here is a linky too one of the 3130's i came across modded
NAD 3130 Stereo Integrated amplifier Modified Uprated Performance | eBay

NAD 3020 3130 3225 Excellent Audiophile Upgrade Repair Restoration Service | eBay

One thing i have noticed is caps have gone up in price since i last bought some, anyone know where you can get good ones for a bargain price?
Cheers for posts all.
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Old 8th April 2013, 06:38 PM   #7
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i just cleaned up and modded a buddys 3140 i think it was a 3140 ill check.

first thing you need to do is get some contact cleaner and "simple green"

take the top off and take lots of photos cable postions etc.
then remove bottom plate. unsolder all the wires cables etc so you can get the boards out one by one. mark the cables so you can get them back in right!

clean the boards! G.D. it clean the flux off the bottom....my pet peev!

get a peice of paper and wright down all the electralitic cap values.

order new. as sujested add smaller ones to get total for pwr caps.
replace and clean boards again!
put back together.
clean the switches pots etc with contact cleaner.
ajust the offset and bias.

changing parts.......
first thing i would change would be the offset/bias pots to sealed multi turn type.
second the caps in the signal path to tighter tolerance/quality ones. get rid of the ceramic caps....dont go nutts and get trillion$ ones. just good ones.
third the MJ outputs you talk about are drop in replacements. you will have to reajust for them, but they are what nad used in later models.

nice little setups. need some tlc and another 20years can be had.
i wouldnt go crazy with lots of pricy reworking of the cir.
to be frank its not worth it. it is however worth bringing back up to spec, and changing some components the factory skimped on due to buget restraints.

be careful dont get killed doing it! nothing will make it harder to listen to than being dead!
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Old 8th April 2013, 06:47 PM   #8
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yep 3140. and ive got his 2140 on my bench right now.
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Old 8th April 2013, 07:30 PM   #9
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Wow that 3140 is some beefed up piece of kit looking at some pics I've seen.
It looks to have 2 of the mains transformers that's in mine.
I'm thinking of doubling up on caps and there's Nad doubling up on trannys let alone caps. :lol:

And then there's that enormous heat sink

I am a trained electronics bod by trade, but to be honest my circuitry skills are a bit rusty.
I tend to deal with a lot of electro mechanical stuff these days along with printing equipment and pc/server based stuff.
Most of its plug n play or swap out modular stuff, i never was great at designing circuits etc at component level.
But i would hope i am relatively safe with my soldering iron and multimeter.
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Old 9th April 2013, 01:23 AM   #10
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yah there is 2 xformers. but nothing fancy. its a basic split rail voltage. i havent checked out the scematic on your nad.
the one i messed with has output rails and a regulator cir about +|- 25v for the pre/phono etc.
its a not a bad little setup.
well worth a going through!
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