An excellent power amp from france from the 70's - diyAudio
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Old 14th December 2007, 01:56 PM   #1
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Default An excellent power amp from france from the 70's

Hello

Here's an excellent power amp from france, made in the 70's, it's a Audiotec 70 watt amp.

Bye

Gaetan

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Old 14th December 2007, 04:59 PM   #2
Donk is offline Donk  Europe
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Nice circuit, thanks for posting it.
Anyway it's from the stoneage - I don't think it's worth to build it in 2007...
Maybe it sounded good in the seventies, but now almost any amp (cheaper and simpler amps too!) would beat it.
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Old 14th December 2007, 05:15 PM   #3
acid_k2 is offline acid_k2  Italy
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uhmmm...
a 100V single supply amp....
output capacitor....
and electrolytic caps in the signal path...

this is 70's hi-fi...
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Old 15th December 2007, 02:49 AM   #4
AKSA is offline AKSA  Australia
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Don't dismiss it just because it is old and uses strange schemat layout.... The quality of the concepts is at least as good as many contemporary designs.

Strengths:

Single ended much of the way quasi comp output stage
Regulated front end
Class A input stage with PP EF output and nested feedback
Multiple nested feedback
Full protection with clip indicator]
Elegant phase inverter
Asymmetrical bootstrap
Elaborate, well designed compensation

Weaknesses:

High component count (20 transistors for 70W!!)
Electrolytic couplers and bypasses throughout
6 presets!!
Unipolar supply


The most outstanding quality of this design is the nested feedback and the use of a full on, non-differential input voltage amp and buffer to drive T6, the 'formal' VAS.

France as a country appears to foster 'revolutionary' thinking; just as I like French cars, I like this design, and I can't see why it should attract criticism. That said, of course, I have not heard it, but I'd bet it sounds damn good....

Thanks Gaetan, good circuit!

Cheers,

Hugh
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Old 15th December 2007, 05:12 AM   #5
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Hello Hugh and all the guy's

Yes, it was a damn good amp, as good as Naim, Radford, and other high end amp of the 70's and 80's , I remember the opinion of a very known golden ear guy here in Quebec, he placed Audiotec with the best amp of that time.

I have myself a Radford HD250 from the 70's and even before doing recap it was a damn good amp, now it's even better.

Btw, I know that not much guys would build that Audiotec but it always good to see other amps design.

Bye

Gaetan
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Old 15th December 2007, 05:45 AM   #6
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More than 20 years ago I went through a sort of "conversion" about the merits of French engineering when we bought a secondhand 7 seater Peugeot 'wagon almost by accident as it was the only thing that we could fit all five kids into without having to buy a van. Now it did have some eccentric features but it WORKED WELL and worked reliably for many moons.
But working on it and servicing it brought to mind something that I was told about Europe and the "After life". It was the difference between Heaven and Hell.

It goes like this: In Heaven the English are the police, the Germans the engineers, the French are the cooks, the Swiss the organizers and the Italians are the lovers.
Whereas in Hell the English are the cooks, the Germans are the police, the French are the enginners, the Italians are the oragizers and the Swiss do the loving.
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Old 15th December 2007, 09:29 AM   #7
AKSA is offline AKSA  Australia
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Jonathon,

I LOVE that gag, have always admired it. In Oz we are so far removed from Europe, yet we have European sensibilities, that we can be mightily amused by the strengths and weaknesses of our continental cousins.

I have been an audio designer for about fifteen years, and when I saw the Audiotec design I recognised many of the milestones I have passed in my never ending quest for the holy grail.

Hugh
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Old 15th December 2007, 12:18 PM   #8
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Hello

I've been, for many years, very empress by the technology of a french car, the Citroen.

Here in Quebec, especially in Montreal, we are in heaven and hell... since we are french and english living close together since 400 years and in the 19th century there was coming the irish.

And I'm myself french from my dad and irish from my mom.

Btw, now outside, here in mountain, the temperature are at -31 degree.. brrrrr... and there is a very big snow storm coming tomorow

Bye

Gaetan
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Old 15th December 2007, 12:36 PM   #9
Nordic is offline Nordic  South Africa
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and it is +32C here
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Old 15th December 2007, 12:36 PM   #10
kepa1 is offline kepa1  France
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To partipate in the debate, I always heard that we do have good engineers in France, what we miss is maketers. The local audio market is full of well marketed and good looking English products (with their own particular sound) but I'm not sure you can find many French makes across the Channel...
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