NAD 3020 Rebuild and Upgrade

I have a NAD 3020 that I want to re-cap, but I have some questions about which caps would be the best to use. I plan on using Nichicon caps, so that will limit the field somewhat, but should I use KW audio grade, ES Muse bi-polar, or KL low leakage?

The schematic below shows the phono section of the pre-amp, you can see caps that I've circled in green and red. Green are what I thought should be bi-polar (ES) or low-leakage (KL), and red are audio grade (KW).

Since C401/402 are handling signals straight from the cartridge, I would imagine these would be better as bi-polar?

Phono stage.



The same goes for the tone control stage of the pre-amp, and the power amp. Should I use ES for the ones that appear to be in the signal path, and KWs for the ones that go to ground?

Tone control.



Power amp.



My last question concerns the power supply. I wonder why NAD put two resistors across the rectifier diodes like that?

Power supply.



Lee.

R901 & 902 are bleeder resistors for the C905 & 906.
What kind of caps are currently being used in those positions in the NAD.

avionic said:

R901 & 902 are bleeder resistors for the C905 & 906.
What kind of caps are currently being used in those positions in the NAD.

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All the electrolytic caps in the NAD are no obvious name brand, except for C527 and C528 (bass control) and C601-604 (normal in - power amp), which are solid aluminum electrolytics.

I did think about replacing all the resistors with 1% metal film as well, maybe also the mylar film and ceramic caps.

Lee.

Never replace polarized electrolytics with bipolar ones. This can only result in a reduction of sound quality. Bipolar electrolytic caps are worse than polarized ones, always.

Do not replace mylar or ceramic caps. No performance improvement can be had.

Do not replace resistors. Same business there.

You're wasting time and money. Stop it.

Ruxman said:

Do not replace mylar or ceramic caps. No performance improvement can be had.

Do not replace resistors. Same business there.

You're wasting time and money. Stop it.

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Not really. NAD did bring out a version of the 3020 without tone controls, called the 3120. Magazines at that time wondered how a 3020/3120 would sound with better quality components in it. Resistors aren't going to cost a lot of money, and it's my time to waste.

Way back when, I did "upgrade" a 3020 by running the power amp from a separate power supply with a higher voltage rail. I demoed it at local HiFi gathering, and it surprised quite a few people, it had a much more solid performance in the low frequency range.

Lee.

my nad 1130 has the no name caps all throughout. i too feel a recap is in order after 25 years. through headphones the preamp sounds "good" but not engaging like i have heard from other setups. please post pics of the process if you do it.

I can't find the link (IIRC it was a post by Dave Dlugos on diyaudio.com) but in researching this amp with the intent to rehabilitate it, I did read that replacing all resistors in the 3020 with 1% metal films does result in an improvement. I didn't try it myself so can't quantify or verify but if the amp doesn't sell, I might give it a try this coming winter along with a recap.

leesonic said:

All the electrolytic caps in the NAD are no obvious name brand, except for C527 and C528 (bass control) and C601-604 (normal in - power amp), which are solid aluminum electrolytics.

I did think about replacing all the resistors with 1% metal film as well, maybe also the mylar film and ceramic caps.

Lee.

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I'm not interested in what brand . I'm talking µf values and voltages..You need to stick to these values. Panasonic FM/FC or Nichicon PW/HE.Use Nichicon ES for the bipolar/non-polar signal path electrolytics.

This is my first post with AudioKarma, so we’ll see how this goes..
I’ve just started a recap of my NAD 3020 I bought 30 years ago. This is my first recap project and I’m anxious to get going. I’ve already purchased the Caps from DigiKey but they haven’t arrived yet. The NAD 3020 when first powered up, the power LED flickers for a while, when things settle down after a few minutes, the audio works. I’m hoping the recap project fixes this problem and improves the overall sound quality. Here is a picture of the amp before I've started. I'll post progress pictures, if anyone's interested

bradfro said:

This is my first post with AudioKarma, so we’ll see how this goes..
I’ve just started a recap of my NAD 3020 I bought 30 years ago. This is my first recap project and I’m anxious to get going. I’ve already purchased the Caps from DigiKey but they haven’t arrived yet. The NAD 3020 when first powered up, the power LED flickers for a while, when things settle down after a few minutes, the audio works. I’m hoping the recap project fixes this problem and improves the overall sound quality. Here is a picture of the amp before I've started. I'll post progress pictures, if anyone's interested

Click to expand...

try some new fuses and clean the fuse holders ...they look tired to me with poor connections ...either that or pic is making a couple of them look burnt near one end . not a bad idea to change anyway ..

bradfro said:

This is my first post with AudioKarma, so we’ll see how this goes..
I’ve just started a recap of my NAD 3020 I bought 30 years ago. This is my first recap project and I’m anxious to get going. I’ve already purchased the Caps from DigiKey but they haven’t arrived yet. The NAD 3020 when first powered up, the power LED flickers for a while, when things settle down after a few minutes, the audio works. I’m hoping the recap project fixes this problem and improves the overall sound quality. Here is a picture of the amp before I've started. I'll post progress pictures, if anyone's interested

Click to expand...

What's the serial number of yours? Mine is 3244845. It has the four main capacitors down near the headphone socket, instead of in the middle of the board like yours. There were several versions of this amp, not counting the 3020i they came out with much later on, which I don't think has the massively over-speced 2N3055/MJ2955 output stage. There was a 3020, a 3020A, a 3020B, plus the 3120 that did away with the tone controls.

Lee.

leesonic said:

What's the serial number of yours? Mine is 3244845. It has the four main capacitors down near the headphone socket, instead of in the middle of the board like yours. There were several versions of this amp, not counting the 3020i they came out with much later on, which I don't think has the massively over-speced 2N3055/MJ2955 output stage. There was a 3020, a 302A, a 3020B, plus the 3120 that did away with the tone controls.

Lee.

Click to expand...

Lee

My NAD 3020 serial number is A3221785

I think I just answered my own question. My original post was to try and figure out where low-leakage caps should be used. After all, the NAD 3020 does have a reputation for not having the quietest pre-amp in the World.

Reading through other threads on Pioneer, Kenwood and other equipment, the use of low leakage electrolytics is important in certain key areas of the circuit. Take for example the schematic of a Kenwood KA-7100, which I also just happen to have on my workbench. Here I have circled where low leakage caps have been used. When I eventually get around to re-capping my NAD 3020, I plan on using low-leakage caps in similar areas, as per my original posting.



Lee.

Well, I thought it was about time I posted some pictures of the thing. At the moment, I only have pictures of what it was like once I got the circuit board out of the case. It isn't any dirtier inside than some of the Kenwood or Pioneer amps I've worked on, it just LOOKS worse because of the birds-nest wiring that was a feature of these early NAD amps.



This is a real early version of the amp, the board says revision 1 on it. Here is a close-up of the separate power supply board for the preamp.



Close up of power amp section.



The much renowned phono preamp section.



Tone controls and power amp power supply, the caps are four 2200uF 35v, which will be replaced with something a little bigger.

Replace any caps that are directly in the signal path with film caps. Use Teflon if you have the money, especially on the input caps and coupling caps.

Replace all ceramics with film caps.

Replace all resistors in the signal path. I like PRP for cost/performance. If you have lots of money, replace with Vishay nude or Caddock.

Replace all resistors in the feedback path. PRP or Caddock.

Metal film resistors have a cleaner sound. Caddock can be sterile. Vishay is interesting as they are metal film, yet have a warm sound.

Replace the pots with something better. TKD makes really nice pots.

Replace the power cord entry with a Furutech IEC.

If you do it all, you'll have the only 3020 around with over $1K in parts!

Big E said:

Replace any caps that are directly in the signal path with film caps. Use Teflon if you have the money, especially on the input caps and coupling caps.

Replace all ceramics with film caps.

Replace all resistors in the signal path. I like PRP for cost/performance. If you have lots of money, replace with Vishay nude or Caddock.

Replace all resistors in the feedback path. PRP or Caddock.

Metal film resistors have a cleaner sound. Caddock can be sterile. Vishay is interesting as they are metal film, yet have a warm sound.

Replace the pots with something better. TKD makes really nice pots.

Replace the power cord entry with a Furutech IEC.

If you do it all, you'll have the only 3020 around with over $1K in parts!

Click to expand...

... and the best part is, it probably won't sound all that different than it did before you put it under the knife.

I disagree with most of the recommendations in the quoted post. I'd be particularly wary of replacing all the ceramic caps in the unit with films. If the circuit designer used a ceramic cap in the circuit to decouple ultrasonic frequencies, which is a fairly common use of this type of part, changing to a film cap with a higher parasitic inductance may leave you with a power oscillator instead of an amp.

As I might have mentioned earlier on in the thread, the initial project started out as a re-cap. While I had the thing in pieces, I figured I would swap out the carbon film resistors with metal film. At the risk of repeating myself, reviewers back in the day often wondered on how one of these amps would sound with better quality components. As you can see, they are certainly built down to a price.

With regards to sounding better than before, look at the year of manufacture on the output transistors, 1979 and 1980. Assuming the rest of the components are of similar age, then the electrolytic caps will be around 33 years old. I'm not the only person re-capping stuff on here. Does it make the equipment sound better? Who knows, the only way is to A-B with the same unit that's been re-capped versus one that hasn't. I personally have got two pieces of equipment working again by just re-capping, one was a turntable, the other a power amp.

I'm not trying to create a $1000 NAD 3020 amp here, although if someone offers me that much I'd be a fool not to take it. I'm just enjoying my hobby of electronics and HiFi. I'm not planning on spending vast sums of money on expensive parts, I'm just using Nichicon caps and whatever value metal film resistors Mouser has in stock for pennies each. That said, there are two glass diodes that I thought about changing (after I broke one), they are listed in the service manual as 1N60, there are also a few other listed as BAW62.

Lee.

An NAD 3020 recapped or not is still a budget high end receiver. The electrolytics by now are tired, replace them with good quality capacitors but don't go overboard. Use it as a 30 watts/channel receiver and they are OK. Don't ask more of it.

Here some pictures of the progress I've made so far. There are a few empty spots on the board where the component I've removed doesn't match what was in the service manual. I'm testing every resistor as I remove it just to check the values.



Power supply board.



Power amp close up. The big areas up at the top where there are a bunch of components missing are where the "soft clipping" circuit was. I had no intention of using that, so no point replacing the components.

Keen eyed viewers may also notice the Bourns multi-turn trimmers. There is actually a second pair of trimmers, the NAD service manual suggests swapping out resistors in order to adjust the idle current. No thanks mate, I'll put some trimmers in there.



Phono preamp closeup.



Power amp power supply and tone controls.

Looking good. What are you finding spec-wise on the resistors you've pulled?