NAD 3020 upgrades?

[sennsai]

I recently acquired one of these in original form, just needed a small cap replacing to cure the hum. My present amp is an expensive Rogers E40 driving my Quad 57s, I settled on this after trying dozens of amps over the years, valve and SS.

I got quite a shock when I coupled up the NAD as I found it sounded superior to the Rogers in several ways when driving these speakers! So, I believe it worthwhile to replace the electolytics with the kits from ebay and any other cost-effective change such as signal caps, etc.
If anyone has suggestions, please let me know. One oddity is that the RCA/phono sockets won't accept any modern plug properly, apart from the cheapest varieties.

[paulsherwin]

You will find that most people here are a bit dismissive of 'capacitor upgrades' and will tell you not to bother. You may get a more supportive response on a hifi forum.

Mid 80s amps like the 3020 do sound pretty good, as the designers had got used to working with the available technology by then. The associated 4020 tuner is also a good performer, at least on FM.

[Radio Wrangler]

A long time ago, some truly awful transistorised amplifiers were made and there weren't any particularly good ones around. At the same time, there was a full spectrum of valve amps available ranging all the way from quite good to total crap. If you wanted a good amplifier, you were forced to use valves.

From this, folklore arose and evolved... and now it survives in people who believe that any valve amplifier has to be better than any transistor one. This is not only a ridiculously sweeping statement, it is also long outdated. But some people believe it and they keep repeating it to each other to the point which, for them, it is truth.

Meanwhile, there has been progress made. What was wrong with early transistor amplifiers has been studied, understood, and ways of avoiding it have been developed. Further progress has been made in going beyond what the good valve amps could do in a number of respects.

There is still a place for valve amplifiers. Some people have a perfectly legitimate liking for the modest amount of low-order distortion they add, and if driven into their limits they limit fairly smoothly and don't sound too terrible. Guitarists prefer them because they use this as a sound effect in their playing.

Transistor amplifiers can be made without output transformers and also without DC blocking capacitors on their outputs. This extends their low frequency response as far as you want to go, even down to DC if you really wanted. Without transformer phase shift at the high frequency end, you can employ large amounts of feedback. The characteristics of transistors tend to need this more than valves did, but valve designers couldn't have it even if they wanted it, with the exception of some very peculiar and OTT designs.

So what you've discovered is that solid state amplifiers aren't the spawn of the devil, and that there are some quite good ones out there. You've broken out of the folklore bubble.

It takes guts to believe your own ears, when what they're telling you goes against the pundits. Congratulations!

Some years ago people started going on about 'interconnects' bits of cable to go to speakers and bits of cable with a phono plug at each end. The folklore grew of them having amazing properties to change sound. Prices skyrocketed for bits of wire with esoteric names. To make them look special, the wire got thickened, sorrounded by woven braiding etc. The connectors got trivially thick gold flashing and swelled up in size to the point where they were in such fat housings that many amplifiers had sockets too close to take them. Funnily enough, the bits inside that did the actual connecting were still the same size. It was all fashion. Making hifi cables look like they could tow a ship or jump-start a main battle tank. All fakery, I'm afraid, but it separated a lot of people from a lot of money, and a lot of people still believe it.

David

[Bazz4CQJ]

Originally Posted by sennsai

I got quite a shock when I coupled up the NAD as I found it sounded superior to the Rogers in several ways when driving these speakers!

If it ain't broke, don't fix it. Good as these units are, they are now quite old and so 'invasive surgery' might best be avoided unless totally necessary.

B

[paulsherwin]

The 3020 was notorious for poor build quality, poor switchgear etc. It was a good design and very commercially successful, but it was undeniably built down to a price. The switches are more likely to need attention than the caps.

[AndyWithStuff]

Originally Posted by paulsherwin

The associated 4020 tuner is also a good performer, at least on FM.

Totally agree with that paul, recently acquired a 4020a for less than £20, fully functional apart from a blown bulb on the dial,now fixed.
Made a diy collinear antenna for it and sited it in the loft and FM really sings now. Am is next to useless but no matter.

[audiomagpie]

I've got a NAD 7020 Receiver, the combined tuner/amp version. Looks original and untouched at 40 years old and still working perfectly. Doesn't sound inferior to a higher end Audiolab pre/power combination that I currently have set up. As I remember their products were UK designed and assembled in the far east, and probably still are..

I don't think it'd benefit from any upgrading if it's working to original spec., as already said above emperor's new clothes, etc.

[stevehertz]

Originally Posted by Radio Wrangler

A long time ago, some truly awful transistorised amplifiers were made and there weren't any particularly good ones around. At the same time, there was a full spectrum of valve amps available ranging all the way from quite good to total crap. If you wanted a good amplifier, you were forced to use valves.

From this, folklore arose and evolved... and now it survives in people who believe that any valve amplifier has to be better than any transistor one. This is not only a ridiculously sweeping statement, it is also long outdated. But some people believe it and they keep repeating it to each other to the point which, for them, it is truth.

Meanwhile, there has been progress made. What was wrong with early transistor amplifiers has been studied, understood, and ways of avoiding it have been developed. Further progress has been made in going beyond what the good valve amps could do in a number of respects.

There is still a place for valve amplifiers. Some people have a perfectly legitimate liking for the modest amount of low-order distortion they add, and if driven into their limits they limit fairly smoothly and don't sound too terrible. Guitarists prefer them because they use this as a sound effect in their playing.

Transistor amplifiers can be made without output transformers and also without DC blocking capacitors on their outputs. This extends their low frequency response as far as you want to go, even down to DC if you really wanted. Without transformer phase shift at the high frequency end, you can employ large amounts of feedback. The characteristics of transistors tend to need this more than valves did, but valve designers couldn't have it even if they wanted it, with the exception of some very peculiar and OTT designs.

So what you've discovered is that solid state amplifiers aren't the spawn of the devil, and that there are some quite good ones out there. You've broken out of the folklore bubble.

It takes guts to believe your own ears, when what they're telling you goes against the pundits. Congratulations!

Some years ago people started going on about 'interconnects' bits of cable to go to speakers and bits of cable with a phono plug at each end. The folklore grew of them having amazing properties to change sound. Prices skyrocketed for bits of wire with esoteric names. To make them look special, the wire got thickened, sorrounded by woven braiding etc. The connectors got trivially thick gold flashing and swelled up in size to the point where they were in such fat housings that many amplifiers had sockets too close to take them. Funnily enough, the bits inside that did the actual connecting were still the same size. It was all fashion. Making hifi cables look like they could tow a ship or jump-start a main battle tank. All fakery, I'm afraid, but it separated a lot of people from a lot of money, and a lot of people still believe it.

David

David, you've kinda encompassed 'all' that I think about or have to say about the evolution of hifi in the past 60 years. So true. And yes the 3020 is a great amp. Built like a rat's nest, but try telling the audio molecules that..

[GrimJosef]

Originally Posted by Radio Wrangler

A long time ago, some truly awful transistorised amplifiers were made and there weren't any particularly good ones around. At the same time, there was a full spectrum of valve amps available ranging all the way from quite good to total crap. If you wanted a good amplifier, you were forced to use valves ...

If by 'quite good' you mean good enough that no human on earth could distinguish them audibly from perfect at a distance of more than 500mm from the speakers (if you were crouched closer than that in the quietest of rooms then you might just be able to make out some amp noise) then I'd agree.

The valve amps cost more to make (transformers), ran hotter, could be a bit prone to long-term drift and were individually power-limited which was a problem if your job was providing the PA for stadium rock. But if all you wanted to do was to listen to music in a domestic environment then you could buy a valve amp in the early 60's which was good enough that you, as the listener, would never hear a better sounding solid-state one.

I agree with the other stuff too (as long as we're not going to get into the sticky stuff over whether belief can make the listening experience better).

Cheers,

GJ

[evingar]

Originally Posted by paulsherwin

The 3020 was notorious for poor build quality, poor switchgear etc. It was a good design and very commercially successful, but it was undeniably built down to a price. The switches are more likely to need attention than the caps.

I had one of these from new and was really impressed with the quality of the sound. Unfortunately I can't vouch for the longevity of the switch gear becuase some ing (rhymes with runt) broke in and stole it !

[qualityten]

I did some work on a NAD 7020 (same amp with a tuner) about three years ago, with help from kind members here. After a small repair and some unnecessary oscillation hunting, I went on to replace nearly all of the electrolytic capacitors.

It was fun tidying up the PCBs (the Taiwanese soldering was quite messy) and it was reassuring to know that it had fresh capacitors for the future. It sounded good and is being enjoyed by a new owner.

So, I would say recap away. It's a pleasant way to spend some late winter evenings and you won't break the amp if you work carefully. In post #64 you will see a pile of the capacitors I replaced. The thread is here: https://www.vintage-radio.net/forum/...light=NAD+7020

[Radio Wrangler]

I'd add that transistor amplifiers can be a right so-and-so to fix if they get blown up, so if you're going in to do any work, go slow and sure. Double check capacitor polarity, value voltage very carefully before applying power.

It is possible to repair the things, but it isn't an enjoyable experience, and trying to do the fix in little stages can lock you into perpetually circling through the same replacements.

David

[Bazz4CQJ]

My 7020, bought new around ~1987, is still in perfect condition - no problems at all. Sadly, the sibling 6325 cassette deck has developed problems with the transport mechanism, and I've spent enough time trying to sort it out, and have decided to call it a day .

B

[Station X]

I bought my 3020 around 1979. It's still in daily use and working well.

I'd no more think of changing the capacitors than I'd think of changing the air in my car's tyres. It isn't as if these amps are full of wax paper dielectric Hunts capacitors.

[Boulevardier]

Originally Posted by Radio Wrangler

I'd add that transistor amplifiers can be a right so-and-so to fix if they get blown up, so if you're going in to do any work, go slow and sure. Double check capacitor polarity, value voltage very carefully before applying power.

It is possible to repair the things, but it isn't an enjoyable experience, and trying to do the fix in little stages can lock you into perpetually circling through the same replacements.

David

I so much agree with you David, - in fact I’d go so far as to say that DC-coupled power amplifiers are rarely economically repairable. You maybe start by replacing faulty-testing semiconductors (because you can’t take meaningful voltage or current readings when they’re faulty, or when there’s a fault just about anywhere in the circuit). Then you apply power (even current-limited) and something blows again because either (a) the original fault was caused not by a failed transistor, but by a failed capacitor or resistor - which is still there, or (b) a transistor did cause the original fault, but that damaged another component which caused the second failure. You just don’t know, because there are almost no meaningful measurements you can make during the fault conditition, and you may have to go through this replacement rigmarole every time you try to apply power.

The only practicable and quickest approach seems to be to test or replace just about every component in the circuit (you’re going to have to disconnect one end of most of them to test them anyway, so might as well just replace them - resistors and caps and small-signal semiconductors are cheap enough).
But then if you’re going to replace all those, you’re effectively installing a "new" PA. The total cost of parts + time is almost certainly going to be greater than that of a new PA board. And then you’ve got to convince a paying customer that it was that difficult and time-consuming to repair. If you’re just doing it for your own use, then time isn’t a factor, and pig-headed determination may get you there in the end. But it’s still a deeply frustrating process.

I think the advent of DC coupling and the loss of inter-stage couplng capacitors heralded the end of sensible fault-finding and economic repair! But then I haven’t had the vast experience that others here seem to have had, and maybe they would feel differently...

Mike

[qualityten]

My comments on repairing and then recapping my 7020 are made strictly from a hobbyist's perspective, where time spent with a soldering iron and checking polarities is a relaxing change from the very different day job.

It is true that I only found one faulty capacitor, and that thanks to astute guidance from members here (especially Paul Sherwin and Radio Wrangler). But that did make me wonder why it failed and whether any of the others of the same age and type might also be faulty.

[Nickthedentist]

I would tend to leave well alone. From what I've seen these are not well put together, and I suspect you could be opening a can of worms by trying to improve things. While it's working, make the most of it and just enjoy it.

See here: https://www.vintage-radio.net/forum/...ad.php?t=31034

[McMurdo]

I've fixed a few of these old NADS for a dealer, over the years. They do seem to run rather warm, and the electrolytics can fail such that a leg can rot off or cause corrosion. Having said that I did have a leaky ceramic capacitor too..not something one can say every day.

Noisy or intermittent selector switches.
Dry joints.

I think I had a transformer burn out once.

But all these came to me because they'd already failed, not for a trendy upgrade.

IMHO an upgrade would be a new one.

[cheerfulcharlie]

Only had a couple of small dead capacitors IIRC 25uf or something ..soft start dept. caused switch on thump on the speakers... and another one caused hum.

If you want something to do you could probably change the volume pot for a modern one, as they can be randomly crackly these days.

[Radio Wrangler]

Originally Posted by GrimJosef

If by 'quite good' you mean good enough that no human on earth could distinguish them audibly from perfect at a distance of more than 500mm from the speakers (if you were crouched closer than that in the quietest of rooms then you might just be able to make out some amp noise) then I'd agree.

Yes indeed. Mankind has known for several decades how to make amplifiers sufficiently good that their impairments fall below thresholds of perception, and are trivial compared to other parts of the chain between, and including, performance and lug 'ole.

40 years ago when I was playing with ideas for a new amplifier to drive a somewhat awkward pair of new speakers, I designed and built three amplifiers. One was all-valve (apart from power supplies) The other two used Bipolar and Mosfet output stages respectively, and were closely related.

Friends, including a few hifi nutters, a few musicians and a goodly number of engineers got to try them. No-one could tell them apart.

The valve amplifier was transformerless and DC coupled. It's a very hard act to pull off. The thing was a monster and the total amount of heater power was ludicrous. A stereo pair simply wasn't going to be practicable in a smallish living room. 40 years ago the valves were very cheap. people couldn't give common types away. I dismantled it when I'd had my fun with it. The effort that went into it could not be justified in any rational universe, but that is a freedom you have in what you do for a hobby compared to what you do for fun.

One of the solid state power amp designs got turned into PCBs and a stereo pair sit in a cabinet between my speakers to this day. Total repairs and changes amount to a couple of surrounds for the K040 midrange drivers in the speakers. The preamp is more troublesome. Every couple of years I have to clean the contacts in the silver alloy stud fader used as the volume control because it goes noisy. There are some high value resistors in the input selector switching which fail. There's a couple of dozen of them, 22 megOhms, and I seem to get one going high every several years. If these failures were simple random happenstance, the MTBF would calculate out as dozens of years and not seem so bad. But it's not random, there is a common ageing process in each part. Some chemical clock is ticking away in each resistor.

It's a nuisance, but its interesting that the rest of the electronics has been hassle free.

The business of designing a good amplifier which faithfully reproduces whatever you feed it may have been all done and dusted a long time ago, but there are still good and bad amplifiers. Often it comes down to quality of construction and parts affecting reliability. Some people still make bad sounding amplifiers, sometimes to save cost, sometimes through limited knowledge, and (sadly) sometimes to incorporate some pseudo-religious cult theory.

So long as we dodge the awful amplifiers and the badly constructed ones, we still have a free choice of many approaches, many types of devices, and many models of each.


Regarding fixing solid state amplifiers:

In a DC-coupled transistor power amp, most forms of failure result in the destruction of a number of parts, usually the most expensive ones. On the whole the total parts cost is small. Replacing everything on the power amp board and heatsink is a valid repair technique which can save a lot in time, especially if you're paying for that time.

If you're doing it for a hobby, and your hobby isn't accountancy, then you may want to do the fix the long way round for its educational value. You may be interested in the forensics of it... What went wrong and in what way did the chain of dominoes fall?

If you're a manufacturer, you may need to take the accountants on one side for a wee chat, to explain that thoroughly investigating failures will allow you to revise the design and cap future warranty costs. They'll like this, maybe not as far as buying you a pint, but you'd get their support if you applied to join the golf club.

If you're a good designer, you'll know that there are ways to run individual stages with test jigs built around them to provide feedback and bias control as needed. This is how you do the development of those stages. The amount of time involved would not make sense for a repair, It would be cheaper to order up a new Krell or something. However, if you're not charging for your time and you want to discover and learn, then why not?

Because we're doing it for fun, commercial considerations don't necessarily apply.

I've had my fun out of it. That amp in the living room means an awful lot to me, but it will mean an awful lot less to anyone else. Anyone else would miss out on the 'Wow! I did that!' factor, and that's where the real fun is.

It's been good hearing about Andy, Diabolical Artificer's exploits with his amplifier developments. He's gone down different paths to me, inevitably, but he's had immense fun and he got the pure 'I did that!' factor.

On 'Upgrades'

Most of what people apply this word to, aren't

If they improve the sound, there had to be something rather wrong in the first place.

Reliability and ruggedness improvements are more sensible.

David