Tom, I mourn nothing because I lost nothing. If anything in my life has served me brilliantly, it was my view that (my) honour was not negotiable and was the exact opposite of flexible. The fear of betraying it in form of my word made sure I was never once late (though sometimes in the nick of time), I never once failed on a job I took, etc. In short, I never once failed to make good my word.
My word is really the only capital I have. I am - obviously! - unwilling to squander it. BNecause of this, my circle of customers was always made up of repeat trade by at least 40, and now 80%. People get used to reliability oh so easily. And personal honour does translate into reliability eventually.
Remember, I am self-employed, and sleepless nights are what I sometimes have to pay for that luxury. My wife and I got married on a Sunday, we kicked my best man and his harmonica out at 2 AM, and by 8 AM, I was hitting the typewriter (February 1984, PCs still scarce and expensive like hell, but I did get an IBM PC four months later).
As for your MAYBE, let me assure you, no maybes about it, it's a sure thing. Not only for you, but for all of us. You see, when you live in any system, sooner or later you will start to take same aspects of it for granted simply because you're too used to them; true for all of us, myself certainly included. It sometimes takes an outsider to draw your attention to this or that, which has always been there but you started not to notice. A very human trait.
And without personal honour, there can be no national honour. No exceptions.
If we mourn it, then we should be honest enough with ourselves to ask ourselves: how did all this greed appear? It was always there, but kept in check by various social mechanisms, which were eventually overwhelmed and today, greed runs rampant on a global level.
Personally, I refuse to get in synch with that. I know I am far from being alone, but I also realize that those who refuse to let greed run their lives are a definite minority today, anywhere. And the pied piper will come to collect on his bill.
dvv,
It is obvious from your post that you are a wonderful human being, with a beautiful heart and mind.
Maybe I even have an "internal fault", but I see one or two things in a sort of opposite polarity, maybe as if from the other side of the glass, so to speak. I will try to explain what I mean, but as briefly as I can.
(Moderators: This is not political. Just history.)
Economies and societies and cultures are degrading, and seem to have been changing for the worse for a long time; at least 50 years.
Many people like to lay a lot of the blame for that on increasing Western tendencies toward socialism and liberalism/progressivism, which seem to be closely correlated, both with each other and with the degradations mentioned above.
Greed and capitalism have been demonized by the people who seem to be responsible for the ongoing degradations mentioned above, as well as the tendencies mentioned above.
I don't want to get into anything political rather than historical, so I'll just state that it is "extremely likely" that neither side had, or has, less-than-average greed. Greed is normal, in humans, and without it nothing at all would get done. For example, I am often excessively greedy... for new scientific knowledge. Is that immoral?
So, I am postulating that you are casting the blame in the wrong place, when you blame greed. Greed was, and is, not part of the problem (except maybe for the greed of the created "victim class").
At this time, please, and this is very, very important, please watch the following famous video: http://www.youtube.com/watch?v=F0VHiONkot8 (and also the other segments of it, linked there).
Maybe I don't need to say any more about that.
A bit of a parallel between us: I was self-employed for 24 years, starting in... February 1984 (after I resigned from my first engineering job, to start a software company). I had some Apple IIe computers, but they weren't quite up to the task. I waited eight months instead of your four months. But I bought two IBM PCs instead of one. And yes, wow, they were extremely expensive back then. (I had a friend who was an engineer at IBM and he got them for me, with an employee discount. They cost me over $2600 each, with 640k of RAM and one 360k floppy disk drive (and NO hard drive), and a monochrome monitor.) But they were ten times faster than the Apple IIe. There is a lot more to that story, and the conditions we endured would raise some eyebrows, for sure. But it's too much to go into, here. (And you already know exactly what it's like.)
Thank you, so very much, for sharing your personal thoughts.
Regards,
Tom
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Tom,
About me - thank you, I only wish it were true. I get quirky and fidgety like everybody else, maybe less than most. I have my bad days, like everybody else. I haven't made too many mistakes in life, although of course I have my share, and fortunately, none of them impacted others, only me and my family. I speak my mind, or shut up, no in betweens. I eat too much. I smoke. Too many faults to make me even a candidate for really good.
On greed - the problem is not greed as such, but the seemingly no measures and social norms to keep it in reasonable check.
Greed has been around for as long as man has, and is in no way "blameable" on any system, but what is every system's measures and means to keep it in check. It will never go away no matter what we do, so elimination is out of the question, leaving only control, which can be lesser or greater.
"The last 50 years" coincides with literal doubling of the world population, making it hard for any system to cope In addition to the objective problem, we also have a subjective component that for the love of power, far too many leaders-politicians are simply refusing to face facts because they don't really know how to go about solving them, and are really concerned only with their own re-election. This rules out any serious actions, many of which take years, if not decades, to show results. Again, this has nothing to do with system or counttry, it's more or less the same all over the globe.
Because this is so, it's very hard to lay blame at anyone's specific door for many things, even if the USA is the usual suspect, my feeling is that it's only the first because it's the most developed, but experince shows that US trends are dutiufully copied by others with zero discrimination.
Only specific events can be blamed on someone with any hope of being at least half right.
On the IBM PC. At the time i bought mine, in 1984, the PC was on the USA/NATO list of technologies which cannot be exported. So I had to go to London to buy mine. When I added up the total cost of traveling, purchasing, customs when returning, it worked out as almost exactly equivalent to purchasing 4 locally made cars. Like you, no hard drives, just two 5.25" floppies.
Also probably like you, by 1987, the hard drive was there, and more, an Orchid turbo card was inside. This card was in fact a parallel computer, and unlike most of the day, it actively used the PC for handling the peripherals, while the actual processing was done on the card, by an 80286 running at 8 MHz, with zero wait state RAM. Hellishly fast, beat most natural 80286 ATs in most tests.
Ah, those were the days, we had so much enthusiasm then.
Tom, we can pick up on the subjects mentioned, but if we do, let's do it via private mail, rather than here. Or on the subjects not (yet) mentioned, which are even more interesting.
About me - thank you, I only wish it were true. I get quirky and fidgety like everybody else, maybe less than most. I have my bad days, like everybody else. I haven't made too many mistakes in life, although of course I have my share, and fortunately, none of them impacted others, only me and my family. I speak my mind, or shut up, no in betweens. I eat too much. I smoke. Too many faults to make me even a candidate for really good.
On greed - the problem is not greed as such, but the seemingly no measures and social norms to keep it in reasonable check.
Greed has been around for as long as man has, and is in no way "blameable" on any system, but what is every system's measures and means to keep it in check. It will never go away no matter what we do, so elimination is out of the question, leaving only control, which can be lesser or greater.
"The last 50 years" coincides with literal doubling of the world population, making it hard for any system to cope In addition to the objective problem, we also have a subjective component that for the love of power, far too many leaders-politicians are simply refusing to face facts because they don't really know how to go about solving them, and are really concerned only with their own re-election. This rules out any serious actions, many of which take years, if not decades, to show results. Again, this has nothing to do with system or counttry, it's more or less the same all over the globe.
Because this is so, it's very hard to lay blame at anyone's specific door for many things, even if the USA is the usual suspect, my feeling is that it's only the first because it's the most developed, but experince shows that US trends are dutiufully copied by others with zero discrimination.
Only specific events can be blamed on someone with any hope of being at least half right.
On the IBM PC. At the time i bought mine, in 1984, the PC was on the USA/NATO list of technologies which cannot be exported. So I had to go to London to buy mine. When I added up the total cost of traveling, purchasing, customs when returning, it worked out as almost exactly equivalent to purchasing 4 locally made cars. Like you, no hard drives, just two 5.25" floppies.
Also probably like you, by 1987, the hard drive was there, and more, an Orchid turbo card was inside. This card was in fact a parallel computer, and unlike most of the day, it actively used the PC for handling the peripherals, while the actual processing was done on the card, by an 80286 running at 8 MHz, with zero wait state RAM. Hellishly fast, beat most natural 80286 ATs in most tests.
Ah, those were the days, we had so much enthusiasm then.
Tom, we can pick up on the subjects mentioned, but if we do, let's do it via private mail, rather than here. Or on the subjects not (yet) mentioned, which are even more interesting.
I am reminded of a very illustrative real world example here.
In the early 70ies, the then managing director (forgot his name, I think its was Piestch, but am not sure) of VW realized that despite wonderful sales figures, the era of the Beetle was over. So he sunk gazillions of Detusche marks into research of a completely new generation of cars. He turned them around, from back engine, rear wheel drive, to front engine, front wheel drive, much like FIAT's 128, which made history with that concept some years before.
He even commited sacrilidge by going to Italy's master designer Giorgetto Giugiaro (Italdesign) for the looks, a job requiring him to create a totally new, modern company look.
And he got the ball rolling all the way, because in his grand scheme of things, VW's daughter company Audi was fully included.
By 1974, most of the funds were exhaused, and sales had started to slump very seriously, while the competition was getting better and better. The new factories were almost finished and slated for commission in 1975.
The board of directors was outraged and promptly fired the man.
Half a year later, the new models, namely the Golf, appeared. It was a hitherto unseen hit, they couldn't make enough of them. Audi was now clearly pitched as their up market company, although they also had the new company looks. VW group's fortunes literally soared, their stock doubled in value in just over 4 months.
Do you think ANYBODY ever went back and said thank you to the ousted director who made it all come true? Not a chance.
One man had a vision and the ability and power to make it come true. He did, and that act eventially turned the VW group into today's biggest car manufacturing company in the world (although they often swap places with Toyota, a very close second). Last year, the VW group sold 2.3 million cars in China alone.
This can happen when someone has a vision and is not greedy, does not think in current and short term, but in the long haul.
Where have such people gone?
In the early 70ies, the then managing director (forgot his name, I think its was Piestch, but am not sure) of VW realized that despite wonderful sales figures, the era of the Beetle was over. So he sunk gazillions of Detusche marks into research of a completely new generation of cars. He turned them around, from back engine, rear wheel drive, to front engine, front wheel drive, much like FIAT's 128, which made history with that concept some years before.
He even commited sacrilidge by going to Italy's master designer Giorgetto Giugiaro (Italdesign) for the looks, a job requiring him to create a totally new, modern company look.
And he got the ball rolling all the way, because in his grand scheme of things, VW's daughter company Audi was fully included.
By 1974, most of the funds were exhaused, and sales had started to slump very seriously, while the competition was getting better and better. The new factories were almost finished and slated for commission in 1975.
The board of directors was outraged and promptly fired the man.
Half a year later, the new models, namely the Golf, appeared. It was a hitherto unseen hit, they couldn't make enough of them. Audi was now clearly pitched as their up market company, although they also had the new company looks. VW group's fortunes literally soared, their stock doubled in value in just over 4 months.
Do you think ANYBODY ever went back and said thank you to the ousted director who made it all come true? Not a chance.
One man had a vision and the ability and power to make it come true. He did, and that act eventially turned the VW group into today's biggest car manufacturing company in the world (although they often swap places with Toyota, a very close second). Last year, the VW group sold 2.3 million cars in China alone.
This can happen when someone has a vision and is not greedy, does not think in current and short term, but in the long haul.
Where have such people gone?
Many years ago Robin Marshal ( BBCLS/5A , Audiomaster , Monitor audio , Epos ) said to me that the main reason that panel speakers sound good is lack of a box . Beyer said the diaphragms of their headphones would accelerate as fast as electrostatic units . B&O made a radio that was classed as hi fi ( Beolit ) . If I understand correctly it used a TV speaker ( Philips ? ) .
It stuck me that often TV speakers are superior to much that is called hi fi . If driving a mid-range with the same signal as a TV speaker often the mid range will sound worse ( I know why , still seems wrong ) .
An idea came . 5 x TV speakers on a panel as a line array . 5 small chip amplifiers perhaps using the magnet and airflow of each speaker for cooling . ( 47 K input = about 10 K ) .
In the ideal world 150 to 7 kHz . Next some selected piezo horns for 7 to 35 kHz . 7 kHz is considered an ideal break frequency ( phase shift and listening fatigue verses practicality ) . 150 Hz also is sensible for keep directional qualities acceptable . I would not advocate a single sub woofer .
The bass would be two conventional boxes that the panels could sit on . I would use guitar speakers as I am sure they are superior and cheaper . Doubtless a bit of alchemy needed to get it right .
This is DIY Audio . This seems ideal . The Mosquito fighter-bomber looked unlikely to succeed . It's " stupidity " of design was even disrespectful enough to withstand bullets !
I said to Robin that BBC research had said that the LS3/5A required 500 watts transient power ideally ( 30 W speaker rating ) . That's nonsense he said . Why I asked ? Because it was he who said it .
It stuck me that often TV speakers are superior to much that is called hi fi . If driving a mid-range with the same signal as a TV speaker often the mid range will sound worse ( I know why , still seems wrong ) .
An idea came . 5 x TV speakers on a panel as a line array . 5 small chip amplifiers perhaps using the magnet and airflow of each speaker for cooling . ( 47 K input = about 10 K ) .
In the ideal world 150 to 7 kHz . Next some selected piezo horns for 7 to 35 kHz . 7 kHz is considered an ideal break frequency ( phase shift and listening fatigue verses practicality ) . 150 Hz also is sensible for keep directional qualities acceptable . I would not advocate a single sub woofer .
The bass would be two conventional boxes that the panels could sit on . I would use guitar speakers as I am sure they are superior and cheaper . Doubtless a bit of alchemy needed to get it right .
This is DIY Audio . This seems ideal . The Mosquito fighter-bomber looked unlikely to succeed . It's " stupidity " of design was even disrespectful enough to withstand bullets !
I said to Robin that BBC research had said that the LS3/5A required 500 watts transient power ideally ( 30 W speaker rating ) . That's nonsense he said . Why I asked ? Because it was he who said it .
Ah! The De Havilland Mosquito! My love of old.
It's such a perverse idea that it could have come only from Britain, nobody else is mad enough.
Building a WW2 airplane of metal and plywood is a feat of engineering. The oldest idea in the book - make it light, then stick in two damn powerful Rolls-Royce engines for mobility second to none. Then add insult to injury by making variations, like bomber, bomber-fighter, fighter, night raider, "Dam Busters" with water surface hopping bombs ...
Only the Brits. You have to bow in respect to such minds.
Later on, Lotus, Reliant and others were built around that philosophy.
A British product which should never be forgotten. Just like the British Seagull outboard motors, which shined on D Day - people are digging them up to this day and using them. I used to own one.
The Americans tried to parry with the Lockheed Lightning, but it never really caught on, although it did its service honorably in the Pacific theatre. But the Yanks were always better with heavy duty stuff, like the Thunderbolt and P-51 Mustang. The Tunderbolt must have sunk about half of the Japanese fleet all on its own.
It's such a perverse idea that it could have come only from Britain, nobody else is mad enough.
Building a WW2 airplane of metal and plywood is a feat of engineering. The oldest idea in the book - make it light, then stick in two damn powerful Rolls-Royce engines for mobility second to none. Then add insult to injury by making variations, like bomber, bomber-fighter, fighter, night raider, "Dam Busters" with water surface hopping bombs ...
Only the Brits. You have to bow in respect to such minds.
Later on, Lotus, Reliant and others were built around that philosophy.
A British product which should never be forgotten. Just like the British Seagull outboard motors, which shined on D Day - people are digging them up to this day and using them. I used to own one.
The Americans tried to parry with the Lockheed Lightning, but it never really caught on, although it did its service honorably in the Pacific theatre. But the Yanks were always better with heavy duty stuff, like the Thunderbolt and P-51 Mustang. The Tunderbolt must have sunk about half of the Japanese fleet all on its own.
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I love the Seagull . Reliable also .
The main reason Mosquito was made was to have unused skills made useful . Same people after the war built speakers in High Wycombe , I doubt those who did woodworking would find it difficult to work in metal . However no training required and perhaps wood was more plentiful ? The D H Comet failed because it was interfered with by outsiders . If it simply had used lower cabin pressure and small round windows it would have been OK ( nor rivets at squarish corners ) . It is my dream to fly in one and a DC 3 . My Maths teacher Chris Bartum built the jet engine in the science museum , he was with Whittle . I only learned recently that the Whittle Jet aircraft prototype was tested secretly about 5 miles from Woodstock where I live . It is said one RAF officer who saw it said " I saw something very strange last night , plane had lost it's propeller and still made a first class landing " . ( jist of it , the one I heard was longer ) .
The main reason Mosquito was made was to have unused skills made useful . Same people after the war built speakers in High Wycombe , I doubt those who did woodworking would find it difficult to work in metal . However no training required and perhaps wood was more plentiful ? The D H Comet failed because it was interfered with by outsiders . If it simply had used lower cabin pressure and small round windows it would have been OK ( nor rivets at squarish corners ) . It is my dream to fly in one and a DC 3 . My Maths teacher Chris Bartum built the jet engine in the science museum , he was with Whittle . I only learned recently that the Whittle Jet aircraft prototype was tested secretly about 5 miles from Woodstock where I live . It is said one RAF officer who saw it said " I saw something very strange last night , plane had lost it's propeller and still made a first class landing " . ( jist of it , the one I heard was longer ) .
Well, I was luckier than you. I flew quite a bit with the Comet in 1964, and before that with Douglas DC-3 Dakota, modified to be a passenger plane. And a few other turboprops, like the Viscount. AND the DeHavilland Trident, which remains my favorite passenger plane ever. And the Convair Coronado, which looks like a Boening 707, witha few detail differences. Once, in winter of '68, I was actually the ONLY passenger in Swissair's Coronado between Istanbul and Ankara - too bad the weather was attrocious.
While in England, I narrowly missed a passenger ride in a Mosquito. Some old RAF blokes were flying tourist rounds, 30 minute flights from one of those RAF abandoned, civillian teakover airfileds all over Britain. I regret not making it to this day, but it appears I was one of the very few wanting to do it, most wanted to go to Ilfracombe, so we went to Ilfracombe on a majority vote.
As for the Mosquito, I think you are wrong, Nigel. The RAF wanted a medium range fighter, night fighter and light bomber, for odd jobs like dam busting in Germany, where no other available plane could manage the required relatively low speed for dropping the hopscotch bombs, followed by a violent upwards climb, combined with the required range. The Spitfire and the Hurricane were fine as fighters, but that was it. The Beaufort was nice, but underpowered for supercharged tasks, the Lancaster was too big and heavy for fast work.
I have read in a few places that the Mosquito was more nimble than any other British plane, that it could outmanoever even the Spit. One Spit pilot's comment was thank God the Mosquito was British, because if it were German, he'd be in trouble. I have also read that the only WW2 plane which could run shoulder to shoulder with the Mosquito, even in its forte, sudden steep climbs, was the P-51 Mustang, which was the American dream product, one of those things where everything comes together so well that it makes the next to perfect ensamble. A flying object of beauty, probably the sexiest plane of that age.
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designer round table in May/June 2012 issue of TAS (starting at page 24): http://media.avguide.com/BG_Audio_Electronics_2012.pdf
starring Bob Carver, John Curl, Nelson Pass, Jeff Rowland etc. including the question "Is Class D competitive with linear designs in sound quality, and if not, will it ever be?"
starring Bob Carver, John Curl, Nelson Pass, Jeff Rowland etc. including the question "Is Class D competitive with linear designs in sound quality, and if not, will it ever be?"
I was told that class D is advantageous as it shifts it's switching problems to a higher frequency . It is simplistic to say that , it has the ring of truth to it as I do note an open quality on voices with good class D . Douglas Self has patented ( pending ? ) something which I suspect is somewhere between class G and B which might be the very best compromise . It offsets the switching point from zero volts to higher up . It is still only one switching point . That might be where we should look . I think it also produces more even harmonic distortion which is acceptable . Might even bridge nicely ?
Azur 840W Power Amplifier Cambridge Audio
Going down another route . When designing a simple op amp with booster transistors I notice a point is reached when distortion can be nearly identical regardless of feedback used ( always same percentage more or less cumulatively ) . This is when using complimentary feedback pairs with about 0.7 A standing current as optimum . It comes to mind that the only difference we should hear if so between feedback application is damping factor ? Not so . I have always believed that when the output stage is in more common class AB ( >20 mA standing current ) the speaker should take over the duties of correcting the wave . The amplifier has switched off momentarily and the mechanical properties of the speaker should integrate the points? If the switching is made worse ( class B/C ) it should be only detail that is lost . We all know that is not how it works . So it must be at the moment of release that the feedback loop receives a kick ? My conjecture is the feedback can be as high as you like , however the output stage should have less of it than is usual ( before you say it Dvv that is what you say ) ? I think that is " statements of the bleeding obvious " ? I don't think the reason has been said this way before ? It is not crossover distortion we hear , it is effects of crossover distortion . So relaxing the hold of an output stage on a speaker a littler might allow the speakers spring/inertia/stored energy to do a better job . Can you imagine a piston in an engine being controlled by a viscous damper that stops damping at the mid point of the stroke ? It certainly would make the gearbox backlash work hard ! The class D probably lets go at the top of the stroke which might be better ? The dead period is then the critical distortion mechanism ( the one that prevents latch up ) .
Azur 840W Power Amplifier Cambridge Audio
Going down another route . When designing a simple op amp with booster transistors I notice a point is reached when distortion can be nearly identical regardless of feedback used ( always same percentage more or less cumulatively ) . This is when using complimentary feedback pairs with about 0.7 A standing current as optimum . It comes to mind that the only difference we should hear if so between feedback application is damping factor ? Not so . I have always believed that when the output stage is in more common class AB ( >20 mA standing current ) the speaker should take over the duties of correcting the wave . The amplifier has switched off momentarily and the mechanical properties of the speaker should integrate the points? If the switching is made worse ( class B/C ) it should be only detail that is lost . We all know that is not how it works . So it must be at the moment of release that the feedback loop receives a kick ? My conjecture is the feedback can be as high as you like , however the output stage should have less of it than is usual ( before you say it Dvv that is what you say ) ? I think that is " statements of the bleeding obvious " ? I don't think the reason has been said this way before ? It is not crossover distortion we hear , it is effects of crossover distortion . So relaxing the hold of an output stage on a speaker a littler might allow the speakers spring/inertia/stored energy to do a better job . Can you imagine a piston in an engine being controlled by a viscous damper that stops damping at the mid point of the stroke ? It certainly would make the gearbox backlash work hard ! The class D probably lets go at the top of the stroke which might be better ? The dead period is then the critical distortion mechanism ( the one that prevents latch up ) .
I took this extract below from the Cambridge Audio manual . It says a white paper available for patent application GB050524.0 . I couldn't find it . I suspect the patent didn't go through . Any ideas ? Perhaps it is the old class A op amp trick revisited ( resistor from output to rail ) . Oxford University used that with 741's in the 1970's .
By actively displacing the crossover point this technology creates a
region of pure Class-A operation where the crossover zone would
otherwise be before moving into an enhanced form of Class B at higher
levels. It should not be confused with Class AB, which gives a small area
of Class A, but at the cost of higher distortion as soon as the signal level
moves outside the AB area. Class XD circuitry not only removes
crossover distortion from the zero-crossing point but also reduces
distortion in other parts of the amplifier's output range
By actively displacing the crossover point this technology creates a
region of pure Class-A operation where the crossover zone would
otherwise be before moving into an enhanced form of Class B at higher
levels. It should not be confused with Class AB, which gives a small area
of Class A, but at the cost of higher distortion as soon as the signal level
moves outside the AB area. Class XD circuitry not only removes
crossover distortion from the zero-crossing point but also reduces
distortion in other parts of the amplifier's output range
OK, fine, so make it have low distortion when it does go into class B, and you're home and dry.
So, what's new?
Sorry Mr PP , was designing a PCB today so had littler time to read the PDF link .
Thanks Gootee for XD link .
Reading about the Vincent amp in the Tubecad link . I came to the same reasoning that 4 W is fine for class A operation ( my 0.7A standing current then has transition to AB at that point up to +/16 V rails ) . My feeling is that the crossover doubling effect is acceptable and preferable to being at the sub 1 watt area of conventional class AB . I was pleased to note most of us listen to about 5 watts typical . Thus an op amp with feedback pair outputs and sensible feedback with standing current of 0.7A is a great little amplifier . Use in bridge if wanting more power . I found bias was OK using 2 x 1n4007 and a small resistance ( about 4R7 ) . By chance very stable with 1N4007 fixed with epoxy to the outputs . I did build a Vbe bias , was disappointed that it didn't give me better results although easier to adjust . Cfbp outputs need only 2 x 0.65 V to bias if wondering . Please forgive dia ,it's just my notes ( hope everything is in the right place ) . If trying a similar design try taking the feedback from the op amp alone or half and half . You will find at this current the output stage has very little distortion . OPA 604 was the easiest to get stable I found ( TLO71 and LF351N also ) . The cap on the feedback arm is required for most bipolar input op amps . Even with JFET DC offset is slightly better if it is retained ( 1 mV , 12 mV ) .
Thanks Gootee for XD link .
Reading about the Vincent amp in the Tubecad link . I came to the same reasoning that 4 W is fine for class A operation ( my 0.7A standing current then has transition to AB at that point up to +/16 V rails ) . My feeling is that the crossover doubling effect is acceptable and preferable to being at the sub 1 watt area of conventional class AB . I was pleased to note most of us listen to about 5 watts typical . Thus an op amp with feedback pair outputs and sensible feedback with standing current of 0.7A is a great little amplifier . Use in bridge if wanting more power . I found bias was OK using 2 x 1n4007 and a small resistance ( about 4R7 ) . By chance very stable with 1N4007 fixed with epoxy to the outputs . I did build a Vbe bias , was disappointed that it didn't give me better results although easier to adjust . Cfbp outputs need only 2 x 0.65 V to bias if wondering . Please forgive dia ,it's just my notes ( hope everything is in the right place ) . If trying a similar design try taking the feedback from the op amp alone or half and half . You will find at this current the output stage has very little distortion . OPA 604 was the easiest to get stable I found ( TLO71 and LF351N also ) . The cap on the feedback arm is required for most bipolar input op amps . Even with JFET DC offset is slightly better if it is retained ( 1 mV , 12 mV ) .
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This is a small power amp, right?
I would suggest strongly you couple it with TI BD 249/250 C transistors. They are rated at 25 A continuous, 40A impulse (50A if by SGS-Thomson), they have unexpectedly short Ton, Tstore and Toff times, in C version do 100V, and a nominal Ft of >3 MHz. This last piece of data might put off some people, but it's at their loss.
These are some very musical devices, trust me on this, and are usually very reasonably priced. Their gain factor isn't very high, so I suggest some powerful drivers, MJE 15030/15031 should do it.
I think you would be surprised at what you would hear in the end.
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