Transistor equivalent

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MrAl said:
Mainstream engineering has to worry about cost. The home guy worries about cost too, but since it is a one off they dont have to worry as much.
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Definitely you have a point there! Building just one off, cost is a momentary concern only, with no further effects. Yes.
 
atferrari said:
Hi spec,
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Buen día senior Atferrari

atferrari said:
This is not a rant but a couple of questions.
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It wouldn't matter if it was!


I would go farther than that: if you want a good amp and speakers to listen to and enjoy, don't waste your time building anything- just buy a commercial amp. In the UK you can get a decent amp for around £200 UK and a decent pair of speakers for £120 UK- just wire up and you are all set. That is new; if you buy used you can do much better.

When my house is finished I will be buying new- speakers and amp - no messing about with bits of solder and drilling chassis.

atferrari said:
On the other side, you and so many, dedicate uncountable time to build from scratch amplifiers that hopefully will achieve good (better?) performance if compared with the commercial ones.
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It depends what you mean by 'better' and 'commercial ones [amps]'

There is wide range of amps on the market ranging from the awful to the absolutely out of this world. The prices range from £20 UK up to £50K UK and more.

So how do you choose? What you do is to find the kind of sound you like and the speakers you like because the amp and speakers need to be matched (not talking about impedance here) for a balanced sound that you like. Like all things in life there is sweet spot where the more you spend the less improvement you get. So my advice is to find what you like in both speakers/headphones and then an amp to suit.

To give you a couple of examples, if you have a bright sounding amp and bright sounding speakers the result will be a toppy, edgy sound, and the opposite: a smooth amp and smooth speakers will result in a dull sound overall. This is a complicated subject and I have just skimmed the surface.

atferrari said:
I know there are the audiophools, audiophiles plus experienced DIYers and EEs that can handle the technical part of this.
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Once again, it depends- some hobby amp designers/constructers are in the expert class. They have normally been at it for years and have a thorough understanding of electronics- many on ETO for example. Many are also professionals. They build some incredible amps, which are generally referred to as esoteric or audiophile.

Best not to attempt that sort of amp. Not only are they temeramental and difficult to get working perfectly, but the components cost a fortune: £50 UK upwards for one capacitor, for example, and that is not to mention the transformer, semiconductors, case, and heatsinks.

atferrari said:
Many times as well, I've read, mostly by Audioguru or maybe Nigel, saying things like: "... the XXXXX amp sports a 0,00002% distortion plus -xxx dB of noise, that anyway you will never could hear".
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I have never heard those specific amps, but if they say the amps are superb, they are bound to be. If they are easy to build and well behaved that would be a good way to go, if that's what you want. This is not about those amps but in general- don't overly rely on technical specifications. You can get one amplifier with say 0.1% distortion and another with 0.001% distortion and the first will sound better. The way that the ear/brain interprets sounds is complex and not fully understood, but there are a lot of established ground rules. Just to give you a clue, speakers have relatively high distortion levels, not to mention studio recording equipment.


That sums it up in one. There is the other type who builds to save money, like me when I was a student. I built an amp that certainly wasn't near the audiophile class, but it cost me practically nothing, and it did sound a lot better than the average hifi that most people had at the time. I also built the speakers for about a third the cost of the commercial equivalent.

I listened to that system a lot over the following 10 years and thought it sounded fine. Then I heard a good commercial system- not terribly expensive- and it completely transformed the sound of my records (disks). It was like having a new record collection. You heard sounds that you had never heard before. My amp went in the cupboard, and I never used it for serious listening again. About 2 years ago, I did listen to it and could not believe how bland it was compared to modern amps. Everything is relative!

atferrari said:
Is there a real chance that a single soul could build something that corporate engineering cannot achieve? Probably not so often, isn't it?
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Not a chance, if you are talking about an ordinary single soul. The top amps are 50% engineering and 50% black art. I have heard some home-made amps that are in the audiophile league though. Only a few people have audiophile amplifiers, just like only a few people have Ferrari cars. Most people simply would not notice the difference between a very good amplifier and an audiophile amplifier, especially as they probably wouldn't have audiophile speakers/phones to match.

If you mean, can the home constructer build a very good amplifier cheaper than one you could buy- definately.


You're a gentleman atferrari.

Audio Amps

Here is a summary of what I think:

(1) If you just want a hifi system to listen too, don't waste your time. Buy one new, or if you are prepared to shop around, buy second-hand. A halfway-house is to buy a commercial amp, even a faulty one, and modfy it with your own circuits. I have done this many times, and in the end all that was left was the case and switches etc. One of the hardest parts of building an amp for everyday use is making the case and this approach gets around that problem. You will also get all the electronic parts from the original to use for your other projects.

(2) If, on the other hand, you want to get some experience of building an audio amp, go for a simple class A/B design with discrete transistors. That way you will get a feel for what is actually going on, and you can still listen to it.

(3) If you just want to build a hifi amp, the integrated circuit approach is by far the simplest and would give the best results, from the little 2W chips thru the LM3886 up to the latest wonders that Audioguru and Nigel are talking about.

(4) As for audiophile amps, I don't want to put you off, but I would leave that for a while. The normal amps are very good these days anyway.

Finally don't worry about asking questions, however basic. I for one, would be only too pleased to help out as would many other members on ETO, I'm sure. And you didn't high-jack this thread at all: if you want to see high-jacking just look at some of the stuff I have posted here. By the way, if you want to PM me any time, go ahead.
 
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The way this thread's progressing, maybe it needs a new title?

e.g. Criteria for building a low coast audio amplifier - Lots of time and no money.
 
Who is Rod Elliot?
 

From Eliot sound products:
Another type of Class-A amplifier uses the same circuit as Figure 1, but the transistors are biased to around ½ the peak speaker current. With signal, the transistors can draw up to double the quiescent current at waveform peaks, or zero at the opposite peak (one transistor will be double and the other zero as the waveform alternates). Dynamic analysis of this arrangement is harder than either of the other topologies described, but if we examine the quiescent state and the maximum output, a reasonable estimate is possible. Using the same values as before, we have 20V across each transistor, at a quiescent current of 1.25A. Each transistor will therefore dissipate 25W with no signal, and maximum power is also 25W. Efficiency is therefore ...

Eff = 25 / 50 * 100 = 50%

The amplifier that I am proposing has an efficiency of 40W/98.8W= 42.19%

Dropping Hfe happens in all transistors in all amps, both at low currents and high currents.

You won't get much more distortion than from a class AB amp, where the current goes from 0A to Vopmax/RL. The maximum current that the output transistor has to handle is exactly the same for both class A and class B amps, for the same load and output power.

Also, the violent change in power dissipation of the output transistors as they go through a voltage cycle, in a class AB amp, itroduces distortion by modulating the Vbe, the hFE and other characteristics.

Not only that, but the driver transistors suffer in the same way. The net result is that the voltage amplification stage has a very difficult load to handle, and it has to go through all sorts of antics to control the output transistor and the driver transistors. This distortion ripples through the amp as the overall feed back tries to correct. This is not too much of a problem at low frequencie, but as the frequency increases, it is a real problem, due to the the falling gain and the need to charge up and down the parasitic capacitances and the virtual capacitance generated by the miller effect. That is why, if you examine the internal wave-forms of a class ABamp, reproducind a sine wave, you often see a sawtooth often with dicontinuites at the middle. It is also the reason why many amps, op amps included, are unable to provide full power at high frequencies.

Finally, the higher temperature of the class A output transistors increases the hFE, which is normally good for reducing distortion. As I have said before, the class A amp is superior in all respects, apart from the obvious: power dissipation (class D is not being discussed here).

In contrast to your fears about class A, the constant power dissipation is a good thing, as far as fidelity is concerned.
 
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KeepItSimpleStupid said:
The way this thread's progressing, maybe it needs a new title?

e.g. Criteria for building a low coast audio amplifier - Lots of time and no money.
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KeepItSimpleStupid said:
There's at least one "bean counter" involved.
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Doing this job for 'nothing' makes it more intresting, for me anyway. Certainly make you think what you are doing. Reminds me of the early days when transistors cost the earth and you would go to all sorts of lengths to use the absolute minimum. And PNP transistors- just forget it. It was the same in computing where the programmers spent ages minimising their code to fit the tiny memory of the first processing machines. Computer mags of the day often had articles about compact code.

Nowadays, 1 transistor, 10 transistors- who cares and as for memory- the same. Some of the deliverable software had large chunks that did nothing, due to changes in the requirement, say. The programmer did'nt remove the code because any mods meant a long and expensive re-test of the whole suite to get the software certified again.

Nicolai's ally casting experiences made me laugh, but he has got me thinking- I've started collectig coke cans already.
 
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Oh, I was said wrong, I want to wind 2 secpndary coils but I wrote primary coils sorry, I was careless.
But I don't understand why we need 24V@500mA coils, supply for what?
Haha, winter is coming to Vietnam since yesterday, have a heater class A may an unique idea, I think if -20°C in Vietnam, it will make anyones FEEL colder than in Canada, my aunt in Russia said "winter in north Vietnam is colder than in Russia cities" the cause by high humidity and strong wind, sometime come with rains.
I will use toroidal transformer if I can collect it from scrap
 
Nikolai Petrenko said:
I think if -20°C in Vietnam, it will make anyones FEEL colder than in Canada
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Canada is huge so some parts have a mild winter and other parts do not say the temperature. Instead the say the number of seconds before your exposed skin freezes.
I was sent to southern USA in winter to fix something and it was warm so I wore a light jacket. Then I was sent to the middle of Canada where it was extremely cold. I did not know how cold it gets there and I had no hat, no gloves, no scarf and no boots.
I went outside from store to store but on the way back to the hotel some of the stores were closed and I needed to run very fast so that I would not freeze.
 
spec:

the answer to Why? https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiMy52bp6_JAhWBFz4KHYpyDiYQFggeMAA&url=https://www.hammondmfg.com/pdf/5c007.pdf&usg=AFQjCNFPNgWFEfkADk5oUMa3KwjgqL3-YA

Bean Counter: I'm not counting the beans in this thread. Just advising that there always seems to be one. Your wife, maybe?

I actually like to buy "value" or something that will last a while, but to drive technology there always has to be early adopters.

I'm listening intently to this thread. Just keeping my mouth closed for the most part. Don't want to get into an argument I cant win.
 
Besides the above, any improvement in current capability is good. For one Z isn't constant and 8 is a 'number". Both damping factor and the "ability" to force current will provide some ammunition against the opponent whose motto is "The current through an inductor cannot change instantaneously".
 

We both made mistakes. That 24V @ 500mA was an error: a hang-over from another power supply where I cut-and-pasted in Eagle. sorry I was careless too! Circuit has been raised to issue 2: transfomer winding corrected and 2 extra diodes added to protect the voltage regulators at turn-off. Can you get LM350, or will I have to think again. It will be as shame if so.

My wife and I were wondering about your origins. Going by your name, we figured Russia.

Not only will the amp keep you warm in the cold weather, but your aluminium smelting furnace too.
 
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Origins? My son has been in Canada all his life but he is naming his new son (and my first grandson will be born in a few weeks) "Jordan" which is a different country and a very wealthy retired African-American basketball player.
 

Got it Keep,

And fully agree. The trouble is , that the 2N3055s are right on the edge, as far as dissipation is concerned, and I am trying to avoid going for parallel pairs as that increases distortion, complexity, and cost. The amp I have on the board, will handle any excess currents that you mention, in the class A mode up to 40W into 8 Ohms, but after that, unlike many class A amps, it wont just give up: it will go to class B.
 
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audioguru said:
Origins? My son has been in Canada all his life but he is naming his new son (and my first grandson will be born in a few weeks) "Jordan" which is a different country and a very wealthy retired African-American basketball player.
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I have always wanted to go to Canada, and one day hope to do the Trans-Canadian rail trip, east coast to west coast. My Dad went to Goose Bay, Labrador with the military. He brought back these huge coats, which were the warmest thing I have ever worn. They used to have heaters in the sumps of the cars, which you would plug into a power supply overnight to stop the oil freezing in the sump. It's about 12 deg C in the south of the UK now, and still we moan about the temperature.
 
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audioguru said:
Rod Elliot is an audio expert in "down under" (Australia, mate). His website has many excellent audio articles and projects: **broken link removed**
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audioguru, on refection I did know of his site. In fact, I used it today to get the heat sink data. Don't take any notice of me. I have an unusual outlook and like nothing more than a good duel. If I didn't think you were a regular guy, I wouldn't bother to repond to your posts, so take it as a compliment. Just imagine the six of us: atferrari, MrAl, Nicolia, you, Tony, and Keep shooting the breeze over a pint of beer- that would be fun, for me anyway.

When I was in research, if you had a design you would put it on the black-board, and anyone, including the cleaner, could pull it to pieces- never mind how trivial. So all of this on ETO stuff is bread-and-butter to me. The only problem is that I am often in discussion on several sites at the same time. We had some really violent arguments, but never personal; that was the rule. And at lunch-time, it was down the pub for a pint, and the unwritten understanding was that that work would not be discussed. Those were happy days.
 
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audioguru said:
Origins? My son has been in Canada all his life but he is naming his new son (and my first grandson will be born in a few weeks) "Jordan" which is a different country and a very wealthy retired African-American basketball player.
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Jordden is a classy name and currently popular in the UK.
 

Keep,
Dont think like that- you were my first friend on ETO! You are family.
 
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