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Old 21st March 2013, 09:12 AM   #8721
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I think I was told by a friend that lead acid batteries are 30 % efficient . He was a financial man which sometime is better than a scientist . His job was to advise people about the realities of industries they would invest in . I have always thought that estimate a bit low .

Graphite or graphene on paper as capacitors ? I say paper as it is easy to do and has respectable dielectric constant . My feeling is the coating is unimportant in audio applications . The next step is to add an electrolyte , surely that puts an end to any supposed sonic advantages ? Silver might just be better as it will lend itself to termination more easily . I seem to remember Philips used lead foil for their polystyrene caps to promote better termination and reliability . If you have a radio that is intermittent put it in a freezer bag in the freezer . Often that will find a defective polystyrene cap ( use your fingers to warm them up ) . GOC/NPO ceramics often will as a substitute , sometimes preferable .
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Old 23rd March 2013, 06:37 AM   #8722
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Click the image to open in full size.

This is an old all NPN op amp . I am tempted one day to build it . I think I saw an all NPN power amp once . OK , 1001 reasons not to bother , still interesting . I like the double LTP and how it clamps the input stage ( 2 LTP base voltages ) . Simple and effective .

Point No 5 probably wasn't taken off exactly as drawn . Better at the node point . +/- 6V seems usually low . I imagine BC 550 C worth trying and 1N4148 .

It seems the real MC1530 was slightly more conventional in it's pin out . +/- 9 V and doing somethings better than LM741 which came later . Less components also . Compensation was external .

Linear Integrated Circuits - D Choudhury Roy - Google Books.
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Old 23rd March 2013, 09:14 AM   #8723
dvv is offline dvv  Serbia
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Any special allure because it's all NPN, Nige?

What is the general benefit, other than satisfying your curiosity?

I can't help noticing that its input stage and VAS look very much like what Otala did in his "no TIM" amp. But he did use NPN and PNP trannies
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Old 23rd March 2013, 09:49 AM   #8724
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Hi DVV . I thought the history of op amps worth showing .In many ways this is far more involved than many amps I see . Because we can have resistor and capacitors plus loads of room we avoid much complexity in power amps . If people bother to read the circuit description it is surprisingly good at what it sets out to do . OK even perhaps the LM358 ( 324 ) betters it now ? That's not the point . There are little tricks used which are still not common in power amp design .

All NPN intrigues me . I wonder sometimes if PNP's make us lazy ? The circuit I just finished must have PNP . It isn't audio . When using valves I use PNP's as they do what no valve can do . It is amazing how many valve builders wouldn't even consider it because it is a transistor . In certain situations it is a shortcut to excellence . Mostly as benign as a resistor when I use a PNP with valves .

I put the MC 1530 up as a Missing Link so to speak . I often wonder if DNA and evolution is a good story ? To me like Alchemy perhaps they are the right ideas with primitive explanations . Too many leaps of the story stated as facts . It is engineering that says this to me and no other thing . I mean no reference to a theist or atheist explanation , I am glad in audio we don't have to guess at what really happened . For that reason we should know a little of how we got where we are .

Last edited by nigel pearson; 23rd March 2013 at 09:53 AM.
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Old 23rd March 2013, 12:02 PM   #8725
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This is an extract I read about MC1530 .

My very first OpAmp design, MC1530/31, circa 1963-64, had 6V/us
slew-rate :-) But it required external compensation.

And it's still being sold, 48 years later...

Obsolete Semiconductors and Electronic Component Part Search - Lansdale Semiconductor | The leader in Semiconductor Manufacturing

I've even had inquiries to re-design it on a modern process :-)

...Jim Thompson


Forgot another bragging point for the MC1530/31... sliding-class-A
output stage... no cross-over distortion ;-)

...Jim Thompson


I found your PDF on it here:

http://www.analog-innovations.com/SE...ngExercise.pdf

I'm not sure how increasing the emitter areas of the output transistors implements the sliding class A.

Without any PNPs for current source loads it must have taken some intuition to arrange things so that everything canceled out and left the output at zero volts!
.

If the output stage does work as stated it is worth looking at . 6 V / is not too bad for something which eventually ran off of 18 V ( was 12 ) . It's gain is approximately 60 x 30 x 5 .


Re: LM324 and crossover distortion
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Old 25th March 2013, 08:32 AM   #8726
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Interesting link sent to me ( thanks Martina ) . If using Quad ESL I see no reason to think it wouldn't be a winner ( damping factor ) . I would build it in it's simplest form as beyond that a conventional amp makes more sense . Interesting to see a silicon device look so much like a triode . Nelson Pass , that should be enough to get some interested .


http://www.firstwatt.com/pdf/art_f6_baf.pdf
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Old 25th March 2013, 07:58 PM   #8727
dvv is offline dvv  Serbia
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Nige, your ability to do at least most of it, if not all, is not in question.

Try as hard as I might, I fail to comprehend the ultimate point of it all.

Call me extreme, but I firmly belive and live by the old AR advertising leaflet from the early 70ies, in which they said that a loudspeaker which is great with classical music but not so good with pop/rock, and vice cersa, are both poor speakers; a good speaker should sound good with anything.

So it is with amps as well, I am convinced - no doubt you could construct a dedicated amp for say Quad electrostatics, but an amp which would not sound very good with some other speaker. To me, that is a flawed amp. I realize that making an amp highly load tolerant is no peanuts, it takes work, materials an money, and there's no way under the sun that it will sound exactly the same with all speakers, but we can get the sound differences to say small, even insignificantly small.

So, if I were you, I'd be thinking about an amp of reasonable power, capable of doing its best with just about anything someone has named a speaker and doesn't cost an arm and a leg in the process.
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Old 25th March 2013, 08:07 PM   #8728
dvv is offline dvv  Serbia
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A small diversion - tonight, despite a shearing icy wind, Belgrade is full of kilts. There are about 3,000 Scots here tonight, to watch the Scotland-Serbia football match tomorrow. And it's just a friendly game, since both teams are out of the next world championship.

I spotted MacLeod, Campbell and a few other known to me clan colours. I admit to being partial to the Scots, the several I knew were excelent people, and my visit to Scotland in 2009 was a true pleasure not often enjoyed. I feel Scotland is a place I could live in easily and comfortably, despite the foul weather.
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Old 25th March 2013, 09:58 PM   #8729
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Quote:
Originally Posted by dvv View Post
Try as hard as I might, I fail to comprehend the ultimate point of it all.
Excellent post, dvv ...

One good system should sound virtually the same as another good system ... because both are getting out of the way of what's on the recording ...

Frank
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Old 26th March 2013, 10:24 AM   #8730
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The point is fundamental engineering . We at last have a reasonably linear output stage . That has to be a good point to start from . One thing I think I never got across is what Bob Stuart was saying years ago . Every time we process the signal through another stage of an amplifier it is a copy . If we define what we need as a minimum standard we should work towards that goal and seek simplicity . Everything else is a caprice . A noble one no doubt ?

Equally an amp like this one of Nelson Pass is a caprice also ?

The point that came through was if the output stage has spare current it can power the feedback loop . I don't know if it is accident or not , he comes up with what was said to be the ideal damping factor of 16 . Beyond that thick cables matter most ( or 3 wire to include speaker terminal feedback ) . The transformer he uses has op amp distrotion levels and is cheap .

We now have an amp where a feedback volume control is likely to work very well . Thus the quieter we run the better everything gets . That usually is not true of modern amps . No volume control between pre amp and power . That has to be a good idea ?

In both Germany and UK Jet engines were not taken seriously . In 1927 they were already becoming realistic devices . Both rockets and jets are simple devices , and it harms them how ?

I noticed recently that the KEF LS 50 speaker has below 1 % distortion . As long as an amp has minimal crossover distortion and reasonable damping factor the 1947 standard of hi fi is still more than good enough ( 0.1 % ) . There " should " be no human on the planet able to say differently ?
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