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Old 23rd June 2012, 04:16 PM   #6291
DF96 is offline DF96  England
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Unusual that; Motorola stuff was usually quite good. They were one of the few manufacturers who actually seemed to like DIYers - maybe a lot of their techies were DIYers too.
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Old 23rd June 2012, 04:41 PM   #6292
dvv is offline dvv  Serbia
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Originally Posted by DF96 View Post
Unusual that; Motorola stuff was usually quite good. They were one of the few manufacturers who actually seemed to like DIYers - maybe a lot of their techies were DIYers too.
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.

Last edited by dvv; 23rd June 2012 at 04:44 PM.
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Old 23rd June 2012, 04:46 PM   #6293
Pano is offline Pano  United States
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Originally Posted by dvv View Post
I know John is neither blind nor mute, but I think you're being a little too hard on him.
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.
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Old 23rd June 2012, 05:03 PM   #6294
dvv is offline dvv  Serbia
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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.

Last edited by dvv; 23rd June 2012 at 05:05 PM.
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Old 23rd June 2012, 05:08 PM   #6295
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Originally Posted by DF96 View Post
Never come across that, except when the number happened to be 1: 1 watt, 2 watts. I imagine it might depend on how the language formed plurals.
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 .

Last edited by nigel pearson; 23rd June 2012 at 05:22 PM.
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Old 23rd June 2012, 05:12 PM   #6296
bcarso is offline bcarso  United States
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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.
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Old 23rd June 2012, 05:18 PM   #6297
Pano is offline Pano  United States
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Originally Posted by dvv View Post
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?".
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.

Quote:
Originally Posted by nigel pearson View Post
I think we have a good rule of thumb for capacitors now . 22 000 uF as many times as you can afford.
A nice, scientific way of going about it, eh?
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Old 23rd June 2012, 05:20 PM   #6298
tvrgeek is offline tvrgeek  United States
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"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?
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Old 23rd June 2012, 06:06 PM   #6299
dvv is offline dvv  Serbia
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Originally Posted by tvrgeek View Post
"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?
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.
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Old 23rd June 2012, 06:16 PM   #6300
popilin is offline popilin  Argentina
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Originally Posted by john curl View Post
The actual needs from a power supply are not easily put into a single catagory or two.
And it is usually 'relative' rather than absolute, so you can not just compute the ideal solution. Usually, more is better, unless you go to extreme excess.
Less will work, but not as well. It should be obvious, but many people think that they can get an equation for optimizing an analog power supply, but there isn't any.
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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