Good memory, i'd say.
(overhere it's easy, volt/ohm/ampère sound incredibly strange when pronounced with an added s. One advantage the French lack
)
Thanks DVV, at least that's a bit of info and a start. And provieded by someone who has built a few amps, Motorola.
Much better than:
Which tells me, basically, nothing. How can one learn to design from that?
Certainly I don't expect to get a rigid formula, but knowing what you might need to overcome ripple is a starting point. After that we might be talking about what the extra energy can do for sound quality, either objective or subjective.
Many of the amps I've liked over the years have stored massive amounts of energy compared to the power dissipated into the load. That might be a low power amp with a disproportionately large PSU, or an amp designed for much higher powers than it's used at. (High power amp used on efficient speakers at home).
It would be interesting to know from amp builders who have experimented with this if they've found a point of vanishing returns. Or a point of "good enough." Beyond ripple reduction (which DF9 has outlined) what are the advantages of more stored energy? Or are there any advantages?
Yes, sensible in French has to do with what we call sensitivity in English. The more "sensible" an amp or speaker, the less voltage it needs to reach a certain output.
The adjective is the same for people, too.
Chapeau!
Something like that is what I was looking for.
Thanks.
Don't worry it doesn't matter, in this thread is a minor detail.
We have almost one hundred post talking about ... Economy.
Shouldn't that be "joules"?
There is no place for philosophy of language, here the units are €, £, US$, etc.
I found the app note - Motorola AN1308, featuring a 100 WPC and a 200 WPC power amp, based on their MJL 3281/1302 power transistors.
The said formula is in the "Designing the power supply" section, and yes, it does require a division by 2.
I stand corrected.
When you see how it's all typeset, you'll also see why it is so easy to leave something out. Good app note, awful typesetting, formulas should never be included in a line as regular text, they should always be set apart.
Sorry, Pano and Popilin, my bad.
The said formula is in the "Designing the power supply" section, and yes, it does require a division by 2.
I stand corrected.
When you see how it's all typeset, you'll also see why it is so easy to leave something out. Good app note, awful typesetting, formulas should never be included in a line as regular text, they should always be set apart.
Sorry, Pano and Popilin, my bad.
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I know John is neither blind nor mute, but I think you're being a little too hard on him.
I asked him specifically, a few pages back, what would he consider to be the right amount of capacitance for a nominally 100 WPC/8 Ohm amp, and he very specifically said 22,000 uF should be good. I assumed he meant per channel, although that was not expressly mentioned.
Point is, a very specific question gets you a very specific answer.
But then, John already knew I was in for 4 pairs of 200W output transistors (which arrived a few days ago), so he had a frame of reference. I think THIS is what he refers to - it's one thing to have a PSU capable of great things, but that in itself is not enough to make sure all of that capability actually gets to the speaker, if need be.
Ultimately, designing a power amp is really designing a system, with several subsystems. Inflating any one of them makes no sense, rather we are looking for an even handed approach to it all, remembering that the weakest link in any chain is the weakest link of the whole system.
This is WHY I asked John that. In my particular case, I'm pretty sure I could get away with less, given that my speakers never go below 6.5 Ohms, their worst case phase shift is -25 degrees and they are relatively efficient at 92 dB/2.83V/1m - in my 14 sq. m room. Sheesh, I could get away with a tube amp rated at 10 WRMS easy. By 3 WRMS, my window panes start shaking.
But that's a minimum setup approach, and I don't do minimum setup, EVER. I'm more with Wayne on this, as he puts it "doubling down" (more or less, it can never be quite exact), and I don't build power amps every day.
They are one of the very, VERY few companies I still trust. Ever since I started using their products in the early 70ies, they have never once let me down. Also, I find their rating system to be unusually conservative, just the way I like it.
And another point - if you buy say 10 power trannies from the same batch, I challenge anyone to find such similarity among them from any other source. You could almost use them as is - of course, additional pairing is still a wise move anyway. You may get it down to 5% as is from the shop, but what the hell, why not go for less yet if you can?
Their MJL 3281/1302 transistors come in packages of 25 pcs per rail. With full confidence, I bought just one rail each, that's 25+25 pcs, in firm belief that I will be able to put together two sets of four each which will be down to say 3%, as opposed to 5% the industry at large offers as standard.
Singapore shops charge a premium for a 5% difference from anybody else, definitely including the revered Sanken devices. Which I hate anyway.
And yes, they definitely like the DIY crowd - take a look at their liberal sample purchase deals.
Also, they have been publishing app notes on audio amplifiers forever, I have like three generations of their app notes without even trying. Of course, I'd still rather go for John's work, but truth be told, these app notes were put together by people who very obviously know what it's all about, even if I don't agree with some of their views.
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Shrug... John's just as hard on others, so why not? His response just read to me as either "I don't know" or "I'm not telling." Hard to figure which one.
As I learned amp design from Jean Hiraga, I'm naturally inclined to like over-sized power supplies. For me, they've stood the test of time and listening over the decades. I'm simply interested to learn what others have found, it can't be that obscure a concept. If John Curl or anyone else has a rule of thumb (or better) that they use, it would be nice to know it. The Motorola paper was a great find, thanks.
Being in manufacturig myself, I naturally have more sympathy for John. I realize he's walking a tight line here, between how to be civil about it, yet not give away the work you have slaved for hard for many a year.
I was once told on another forum that it was my DUTY to publish all my schematics for the general good of all ?!? Really ?!?
Unfortunately, in between some really great people you meet on line, there's no lack of crazies. We have become a cheapskate civilization, where nothing but the price matters, and what better price than for free?
My own way out of this is to NEVER, at any cost, discuss any power line filter or "conditioner". Who better than I knows what sort of junk is being sold at what prices in that field, or who really makes the good stuff, yet I have no obligation to advertise anybody. By the same token, I certainly don't want to put anyone down either, especially those I have not tested myself, even if I believe their general approach is all wrong. Even in the "all wrong" group, every now and then you run into a product which is good nevertheless.
Also, most appalicable to John too, is a how a wise man gets out of a self proclaimed genius discussio. Some years ago, I saw Milan Karan do it, and I liked it.
During a local audio show, he was beset by people who thought they know all about it, and typical questions were like: "Why did you use those output devices, why didn't you use xxxxxxx?".
Now, Milan is like 6'7'', net weight like 300 lbs, and I see his face go to a wide smile and he tells this particular nasty: "Tell you what - when you show me something you have made with your own two hands, even if it is only a light regulating rheostat, we'll talk about it." This sure shup up 99% of them.
And if you think Gentle Giants exist in fairy tales only, then you don't know Milan. One of the most gentle and considerate people I have ever met, and still makes the best integrated amp I have ever heard in my life (but of course, there are quite a few I have not heard and would have liked to).
I am truly pleased you liked the app note. Hope you saved it, it's well worth coming back to now and then.
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Dear Peter Platt who said it . We drove him mad by making up various logarithms etc ( Bowmerian logs for my mate David Bowmer ) . Peter was RAF as were most who taught us . My maths teacher Chris Bartram was in charge of the Jet engine that went to the science museum , he made it's pipes ( Whittle Jet ) . He never said when teaching us ( local newspaper ) . He did say the better one gets at maths the worse one gets at arithmetic . That's now the excuse I in all confidence use .
I think we have a good rule of thumb for capacitors now . 22 000 uF as many times as you can afford . Any ideas about the best rectifiers to use ? People say Schotkeys . Not sure I like them . Fast/soft recovery more my cup of tea . Should we suppress them ? I used big 35 A bridges until my friends told me I shouldn't and took them out of amps I made for them .
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I've been following this power supply sizing portion of the thread for a while now, and so far, save anecdotal material, the only inventory of substantial effects and motivations I've seen has come from DF96 and dvv's referencing of the Motorola article. Now there's nothing wrong with anecdotes and shared preferences and experiences. But at least we've gotten some quantitative stuff, and in particular the mention of the power supply rejection of a given amplifier.
Clearly the latter can be widely variable, and provided the rails don't sag to the point of the output devices simply running out of room, the effect on the output voltage will be complicated, and topology and device dependent.
Since we can regulate the supplies ahead of this rather easily, IMO we should, or at least ensure that those earlier stages have excellent power supply rejection.
A couple of other misconceptions need mention: Class A does not entail constant power supply drain. And power supply rejection is not simply a matter of how much loop gain one has.
Clearly the latter can be widely variable, and provided the rails don't sag to the point of the output devices simply running out of room, the effect on the output voltage will be complicated, and topology and device dependent.
Since we can regulate the supplies ahead of this rather easily, IMO we should, or at least ensure that those earlier stages have excellent power supply rejection.
A couple of other misconceptions need mention: Class A does not entail constant power supply drain. And power supply rejection is not simply a matter of how much loop gain one has.
Sure, I hear that at audio shows all the time, it's part of the game. Usually the answer is "Well... you have to choose something, then build it, test, sell it. xxxx seemed the best choice for this product."
At least the folks who ask those annoying questions are interested and involved.
A nice, scientific way of going about it, eh?
"I was once told on another forum that it was my DUTY to publish all my schematics for the general good of all ?!? Really ?!?"
This is the view of all those who scream "Intellectual property should be free!" Of course, this view is held by those who have never had an original thought and don't respect that this is the living for those who do. If you read J.P.Getty's book, How I made My First Billion, he explains how hard reproducing ideas is, and so recommends it as not the way to make money. (Producing a generic commodity everyone needs and uses up is: Oil)
Myself, I have had a few ideas. Failed at marketing, had them taken by others. Whatever. I do appreciate when I get insights from those who can and do. I appreciate craft, and sometimes the only way to understand it is to, well see the schematic. Would one understand how elegant John's floating bias input is without seeing it?
BTW, Is Milan's amp a commercial product?
This is the view of all those who scream "Intellectual property should be free!" Of course, this view is held by those who have never had an original thought and don't respect that this is the living for those who do. If you read J.P.Getty's book, How I made My First Billion, he explains how hard reproducing ideas is, and so recommends it as not the way to make money. (Producing a generic commodity everyone needs and uses up is: Oil)
Myself, I have had a few ideas. Failed at marketing, had them taken by others. Whatever. I do appreciate when I get insights from those who can and do. I appreciate craft, and sometimes the only way to understand it is to, well see the schematic. Would one understand how elegant John's floating bias input is without seeing it?
BTW, Is Milan's amp a commercial product?
Yes, of course it is, as is his behemoth amp delivering 2,000 watts into 8 Ohms, etc. And 5,400 Watts into 2 Ohms.
Something right up Wayne's alley.
Take a peek at Karan Acoustics | Manufacturer of High-End Audio .
I own his integrated amp KA-i180. One of the most natural sounding devices I have ever heard, and the really nice thing is, all his products sound very much alike, irrespective of their price, with bigger you just get more of the same.
But be warned, gentle Milan may be, but his prices are fairly brutal. You get your money's worth, but it's still a lot of dough. Even if it's peanut money for Jacco, according to Jacco.
Without wishing to offend Mr Curl.
A given problem may have no solution.
An equation may have no solution.
But most problems can be expressed by an equation. AFAIK
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