About make an audio power amplifier.

[spec]

Throwing a question here to you Guys....NAD 3020A was a beaut....I have one. Has balls and enough punch to control any speaker.
2 Ohm load no problem...
Regards, tv

So what was the question?

Apologies for answering a question that wasn't aimed at me, but I got tv's meaning right away. As this, and the associated 'Transistor Equivalent' thread, are about making HiFi amps, various commercial amplifiers have been discussed along the way because they have characteristics of note: Leach, Self Simple, Mission Cyrus 1 & 2 and so on. tv is, quite interestingly pointing out, that the NAD 3020 is a milestone audio amplifier of great merit as highlighted by this extract from the Wikipedia page on the NAD 3020:

The NAD 3020 is an iconic stereo integrated amplifier by NAD Electronics, considered to be one of the most important components in the history of high fidelity audio.[1] Launched circa 1978, this highly affordable product delivered a good quality sound, which acquired a reputation as an audiophile amplifier of exceptional value. By 1998, the NAD 3020 had become the most well known and best-selling audio amplifier in history.[2]

https://en.wikipedia.org/wiki/NAD_3020

spec

PS: For those still swayed by audio amplifier technical specifications: total harmonic distortion (THD, inter modulation distortion (IMD), noise, damping factor etc, etc, there is a very telling sentence, also from the Wikipedia article on the NAD 3020:

NAD eschewed the laboratory test equipment thinking, which was prevalent at the time, and instead aimed to make their amplifiers capable of properly driving "real loudspeakers" under realistic conditions. This paradigm shift gave rise to an amplifier that cost less and sounded better.[10][11]

 

[audioguru]

The NAD 3020 amplifier produces a puny amount of output power (20W per channel continuously) that is double (40W) for short duration peaks because its power supply voltage sags. A little more power than my clock radio.
It has a "soft clipping" circuit so that when its output is over-driven it does not sound as nasty as most over-driven amplifiers. Do audiophiles over-drive their amplifiers? Why?

I was pleased by the sound of my Yamaha receiver that produced 78W continuously per channel into 8 ohms but I had two sets of speakers running at the same time for 120W per channel continuously and who knows how much power in short duration bursts because it was never clipping. Its demise was that its selector switch wore out.

 

[tvtech]

Apologies for answering a question that wasn't aimed at me, but I got tv's meaning right away. As this, and the associated 'Transistor Equivalent' thread, are about making HiFi amps, various commercial amplifiers have been discussed along the way because they have characteristics of note: Leach, Self Simple, Mission Cyrus 1 & 2 and so on. tv is, quite interestingly pointing out, that the NAD 3020 is a milestone audio amplifier of great merit as highlighted by this extract from the Wikipedia page on the NAD 3020:

The NAD 3020 is an iconic stereo integrated amplifier by NAD Electronics, considered to be one of the most important components in the history of high fidelity audio.[1] Launched circa 1978, this highly affordable product delivered a good quality sound, which acquired a reputation as an audiophile amplifier of exceptional value. By 1998, the NAD 3020 had become the most well known and best-selling audio amplifier in history.[2]

https://en.wikipedia.org/wiki/NAD_3020

spec

PS: For those still swayed by audio amplifier technical specifications: total harmonic distortion (THD, inter modulation distortion (IMD), noise, damping factor etc, etc, there is a very telling sentence, also from the Wikipedia article on the NAD 3020:

NAD eschewed the laboratory test equipment thinking, which was prevalent at the time, and instead aimed to make their amplifiers capable of properly driving "real loudspeakers" under realistic conditions. This paradigm shift gave rise to an amplifier that cost less and sounded better.[10][11]

Now THAT is worth REP. Spec, if I could, I would give you 100X more than I am able to.
Mike, you too.

Threw it out there. Just for the fun of it.

Going back to the early Eighties. Rotel RA 820 designed by Stan Curtis and NAD were 3020 were all award winners.
Re- wrote the rule books.

I have both amps....NAD is still the robust long lasting killer. Cannot kill it and still plays like an Angel. Sweet sounds without any sweat about the speakers it is driving....

Thanks Guys,
tv

 

[Nikolai Petrenko]

I just realized that audio source like CD players, computer... have high signal strength so preamp it isn't needed. Only phono and cassette players need ones.
I don't know why people buy expensive output speaker cables. I have a piece of speaker cable, cutaway, then I see no difference between it and my ordinary household wire except it has transparent PVC insulator while my wire has red-white insulator. So I decide to use household wires as power supply wires, output and speakers wires.
My wire is 12AWG.

 

[audioguru]

I don't know why people buy expensive output speaker cables.
My wire is 12AWG.

Because audiophools believe that the most expensive things sound best. The expensive (Monster) speaker wire has very little oxygen in its copper (which has nothing to do with the sound) and its seller might say it is also better because it was kissed by a fairy godmother or something like that. I replaced my 18AWG lamp cord speaker wires with 16AWG and it made no difference.

 

[Nikolai Petrenko]

My smallest household wires are 12AWG, bigger ones are 10, 8 and 5AWG. I have measured my wires and see resistances like in standard information table so no problem.
Some expensive wires have silver-coated but I think it only better in non-soldering connecting, while I will solder all connection.

 

[spec]

I just realized that audio source like CD players, computer... have high signal strength so preamp it isn't needed. Only phono and cassette players need ones.

In theory you are quite right, but in practice not. Most high end audio amps need quite high input levels so even the line output from CD players etc is not sufficient to drive the amp. In general, the less gain that an amp has, and by implication the higher the input drive voltage, the less distortion, because for a given open loop gain, quite simply, there is more negative feedback to correct the open loop distortions.

But there is more to it than that. The source impedance into an audio amp effectively forms part of the amp circuit and can have a subtle effect on the amp sound. So it is advisable to drive the power amp from a consistent and well defined low source impedance.

There is also the question of Radio Frequency Interference (RFI). Any piece of wire will have unwanted signals in it. Of course with good system layout and screening and a good OV reference point these can be minimized but they will always be there. Not only are these unwanted signals a nuisance for the obvious reason, but they also cause various forms of distortion.

In short, having a preamp, while in theory is not essential, in practice it is. And don't forget you need a method of selecting the input signal any way.

And if I read you correctly, Nicolai, you will be wanting to add remote control to your HiFi system sometime along the line.

spec

 

[large_ghostman]

Ok found some more caps, I know I have loads more but havnt scratched the surface yet in sorting them out, have a look at these and if they are any good let me know, I can let you have 50 free except for postage at cost if you want them, I will be selling some the others (cheap) if anyone else wants any.

I will post more as I find them.

 

[spec]

Ok found some more caps, I know I have loads more but havnt scratched the surface yet in sorting them out, have a look at these and if they are any good let me know, I can let you have 50 free except for postage at cost if you want them, I will be selling some the others (cheap) if anyone else wants any.
View attachment 97744
View attachment 97745
I will post more as I find them.

Hi LG,
Kind thought; while those caps, are high quality and suitable for general electronics, they are polyester (mylar), and not quite in the same class as polycarbs for hifi audio. They would be ok for general audio though and are not horrific sounding, like ceramic capacitors and many electrolytics.

 

[spec]

Out of context, but I thought you might like this ag:

​

 

[Mikebits]

Hi Spec, and G'day. I found a lot of these caps (see image) in my parts bin. I know they are 4.7 uf caps, but not sure what type they are. There is a polarity marking on them, but they do not look like tantalum's or electrolytic. Do you know what type they are, or anyone else can chime in as well.
Thanks

 

[spec]

Hi Spec, and G'day. I found a lot of these caps (see image) in my parts bin. I know they are 4.7 uf caps, but not sure what type they are. There is a polarity marking on them, but they do not look like tantalum's or electrolytic. Do you know what type they are, or anyone else can chime in as well.
Thanks

View attachment 97747

Hy Mike,
What are the dimensions? Are there any markings on the other side?
spec

 

[Mikebits]

~ 8x8x4 mm, no markings on other side. Thanks Spec.

 

[large_ghostman]

I will keep looking, I know I have reels and reels of caps somewhere, I am bound to have some that are suitable somewhere. Trust the bloody audio guys to be fussy , wernt too fussy when all you had were wax and paper caps thought were you

 

[large_ghostman]

Hi Spec, and G'day. I found a lot of these caps (see image) in my parts bin. I know they are 4.7 uf caps, but not sure what type they are. There is a polarity marking on them, but they do not look like tantalum's or electrolytic. Do you know what type they are, or anyone else can chime in as well.
Thanks

View attachment 97747

G'DAY!!! When did you have a lobotomy Mike???

 

[spec]

~ 8x8x4 mm, no markings on other side. Thanks Spec.

Hy Mike,
I haven't found the exact type, but in view of the style and size I would guess 4.7 uF, 35V solid tantalum, probably made by Kemet, quite old too. If you are prepared to sacrifice one you can put 35V reverse across one in series with a 100R resistor. Keep well out of the way and be careful particularly about your eyes. If it is a tant it may explode or bulge, or emmit some gas. If nothing happens leave it connected for 24Hrs minimum and then check the cap value. If it is a tant I would expect it to be open circuit. Another test you can do is to put a 10K resistor and ammeter in series with the capacitor and connect around 35V, of the correct polarity, across the circuit. If the Ammeter reads any significant current the capacitor is an electrolytic, if not heat the capacitor to 100 deg C and check the current again. Any leakage current indicates that the capacitor is an electrolytic, probably tant. It is just possible that the capacitors are ceramic but they are too small really.

Cheers

spec

 

[large_ghostman]

My scope has those in it, they are def tantalum! Dont reverse them they are like bombs , great fun though , and they are expensive!!

 

[spec]

My scope has those in it, they are def tantalum! Dont reverse them they are like bombs , great fun though , and they are expensive!!

You are not a proper elec engineer unless you have blown up an expensive electrolytic from time to time, either intentionally or accidentally. When I was a sprog the favorite was to connect a 500uF reservoir capacitor across the mains: ally foil and slime everywhere. Another dodge was to charge up the same size cap to 200V and then chuck it for someone to catch.

One morning the test engineer doing the integration of a RADAR system built in a massive mobile cabin had to escape for his life when he switched on. The PSU for the whole rig took up a considerable space and was full of massive 450V electrolytic capacitors. First one blew then another and a chain reaction set in until they had all exploded. Hell you should have seen the mess- ally foil everywhere and the stink was awful, even six months later.

One of the nutters in our billet used to make tea by putting water in a mug and dropping in two copper plates connected to the mains to boil the water.

 

[Mikebits]

Keep well out of the way and be careful particularly about your eyes. If it is a tant it may explode or bulge, or emmit some gas. If nothing happens leave it connected for 24Hrs minimum and then check the cap value.

I appreciate your input and have seen exploding tantalums when I was a factory tech, came out of production that way. Was cool, but I am not sure I would suggest connecting backwards as a test because kids reading these forums may try it and end up getting hurt. The 24 Hr test is really a hazard, what if in hour 16 while you are asleep the cap decides to blow and causes a fire (I have seen PCB's catch fire from backwards tantalums). I guess as a guy who worked as a Safety person I am overly cautious. So I will throw in a disclaimer, folks don't try this at home.

 

[spec]

I appreciate your input and have seen exploding tantalums when I was a factory tech, came out of production that way. Was cool, but I am not sure I would suggest connecting backwards as a test because kids reading these forums may try it and end up getting hurt. The 24 Hr test is really a hazard, what if in hour 16 while you are asleep the cap decides to blow and causes a fire (I have seen PCB's catch fire from backwards tantalums). I guess as a guy who worked as a Safety person I am overly cautious. So I will throw in a disclaimer, folks don't try this at home.

Quite right Mike, but a touch dramatic- if kids or the less experience tried most of the things described on ETO, they would be in danger. Common sense is the key word. The other thing is that with a capacitor that size there would be no major explosion and the reason why, I said to place a resistor in series with the capacitor is to limit the current.

As for the danger of fire when left unattended, once more common sense is the approach- you would put the capacitor in a fireproof container. Your house is more likely to be burnt down by a washing machine (the biggest cause of house fires from electrical equipment) gas cooker, or the many capacitors in your central heating/air conditioning controllers.

spec

PS: I too was a safety officer in addition to my design job- but not one of the jobs-worth obstructive types.