Vintage Brute-70 (40411) clone

[jacques54]

All,

Picked up a heavy black box in a garage sale. It did look like an audio amp and after googling a bit on 'power amplifier 40411' (lots of references to the Tigersaurus found), it turns out to be a european clone of the Brute 70 amplifier as described by E.G. Louis in Popular Electronics, February 1967:

http://www.swtpc.com/mholley/Popular...PE_Feb1967.htm

I wonder whether it makes sense to bring it back to life. At least one of the rectifier diodes have died and the 40411 output transistors might have given up, too.

The only documentation is a tiny schematic where a few components are added by hand, presumably to make it more stable (see attachments). The schematic looks like it comes straight from an Application Note, presumably from RCA. The PE article mentions Data Bulletin ATC-408, but I have been unable to find that one. Any pointer appreciated.

Yes, the box is rather european with it's mains voltage selector (from 110 to 245) and DIN input connector.

BRs,

Jacques

[jacques54]

Some pictures of the box:

http://users.telenet.be/jad/brute70-1.jpg

http://users.telenet.be/jad/brute70-2.jpg

[sakis]

and bulit inside P3a from esp a DX amp from carlos or anything else close .....

the original circuit is almost nothing compaired to the above

[jacques54]

No, I wasn't expecting Nirvana from this unit, but I was just curious about it's origins. Bringing it back to life shouldn't be too expensive, it turns out that one of the big 4700 uF capacitors was short-circuited (leaked), probably caused the faulty rectifier.

It is more the experience of "how does it sound" I'm after, so I try to put it back in reasonable state, but I'm less interested if it's going to blow a few decent tweeters because it oscillates all over the place :-) That's why I was asking if anyone has the RCA Application Note.

Of course, it has a hefty mains transformer (2 x 30 V AC secondary) and a solid chassis. After I have heard it (and possibly blow a tweeter or two,) I will very likely consider recycling it for a Destroyer X or similar.

Cheers,

Jacques

[wg_ski]

Originally posted by jacques54

It is more the experience of "how does it sound" I'm after, so I try to put it back in reasonable state, but I'm less interested if it's going to blow a few decent tweeters because it oscillates all over the place :-) That's why I was asking if anyone has the RCA Application Note.
Cheers,

Jacques

If it still has the 40411's you may very well blow tweeters if you go 'blasting' it. Probbaly won't oscillate at normal signal levels, but very well could when clipping. Those old RCA outputs had issues with sticking and common mode conduction - especially the "PNP" side.

[Uncle Victor]

This is absolutely sure a Carad AAS140 amplifier!
Carad was a Belgium high end audio manufacter till the early 70's.
I have used these amplifiers some 40 years ago - it was in those days the defacto standard DJ amp.
Should have somewhere one, but mine is not so clean as the one on the pictures.
You should not canibalize it - it's a piece of electronic archeology

[tiefbassuebertr]

Originally Posted by Uncle Victor

This is absolutely sure a Carad AAS140 amplifier!
Carad was a Belgium high end audio manufacter till the early 70's.
I have used these amplifiers some 40 years ago - it was in those days the defacto standard DJ amp.
Should have somewhere one, but mine is not so clean as the one on the pictures.
You should not canibalize it - it's a piece of electronic archeology

Thank you for this advice. Can you post an originale broshure from Carad's AAS140 ??
I can't open the URL
http://www.gloeidraad.nl/radioforum/index.php?id=5880

I like such circuits, because until now nobody was able, me to prove, that a modern amplifier circuit blown away clearly this old topology as showed here (from the audible view, not from the view of THD-values), if both topologies are working on a power supply of the same quality.
And the reason therefore is clear for me in the meantime:
Independend of the efforts and complexity by the "front-end" - by idle currents arround 20-50mA through the output stage there is always a limit by the maximum achievable audible sonic quality causes complex THD character. Only by Class-A the acoustical enhancement between an ordinary and a nearly perfect front-end is audible.
By post #13 about
Anybody have scan of AN-483B (Motorola)?
you will find a similar topology - the power amplifier project "Black Devil" (from German's vintage magazine "ELRAD").

[jacques54]

Well, yes, it's an AAS140 because that's what is printed on the back cover... I only wanted to reach a copy of the application note that Carad was using to implement an amplifier.

Originally Posted by tiefbassuebertr

Thank you for this advice. Can you post an originale broshure from Carad's AAS140 ??
I can't open the URL
Nederlands Forum over Oude Radio's - Artikel over Carad AAS26/PPC27 buizenversterker?

This URL points to a question about the combination Carad PPC27/AAS26, a tube pre/power amplifier from between 1961 - 1967. That's a circlotron circuit with EL84 (6BQ5), 2 x 12W RMS.

The only brochure I have seen of an AAS140 shows a small photograph where you see even less than on these photos. The characteristics state 2 x 70W RMS into 8 ohms, but I'll have to look up my scans in order to show this and to tell more...

BRs,

Jacques