JLH Direct-Coupled High Quality Stereo Amplifier

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#24
Andrija, one of my best friends leave in Osijek, Croatia, he can understand your ...

language and i will know exactly what you want to help you.

I already have your schematic, and i need e-mail adress to upload them to you, 2 pages and total is around 2.6 Megabytes.

Come to my personal adress and them i will put you in contact with my dear Croatian friend.

He will explain me how to help you...if he find troubles to help you by himself...he is very good in electronics.....better than i am.

nanabrother@yahoo.com

You are welcome.

regards,

Carlos
 
#27
Jlh - 1972 1993

Geoff said:

Patrick
Done (plus one or two others 😉 )

http://www.tcaas.btinternet.co.uk/index-5.htm

Geoff
Click to expand...


first:
How good website is Geoff's 'Class-A Amplifier Site'!!
It is a goldmine for us.
Thanks, Geoff.


John Linsley-Hood

Between
A Direct-Coupled High Quality Stereo Amplifier (Hi-Fi News November 1972)
and for example
An Integrated Audio Amplifier (Electronics World & Wireless World June 1993)
..... is 21 years!!!

I mean, inside the head of anyone of us 21 years later
and above all what semiconductors we have on market to work with,
there have to be enormous differences.


So to be fair to John L-H,
let's have a look at also the Integrated Amplifier from 1993.
See image from Geoff's site, below.

And to try to be even more fair,
think about that we use eyes of 2007, even 14 years after 1993,
in a branch of electronics that has had a most rapid development.

I mean, like Bob Dylan says: Things Have Changed

lineup

An externally hosted image should be here but it was not working when we last tested it.
 
#31
Re: You are rigth Lineup..i was really bad with Mr. John Hood

destroyer X said:

It was very advance to it's time....
now a days comparison is not really fair.

sorry for that Lineup.

regards,Carlos
Click to expand...


John Linsley is dead ... but he sure is very much alive, in other ways.

So, no need to be sorry, Carlos.
We have to use what eyes we have, today.
Because we have no other eyes to use 🙂

But instead be sorry is very good to be aware.
To be able to put things in correct perspective.


Guess you have sunny and warmth, as usual in Brasil.
This minute we are in middle of winter here.
Last night was -20.5 degrees C.
-20.5 degree Celsius = -4.9 degree Fahrenheit

This is 2 degrees colder, than I have in my deep-freezer.
I might as well put my food out in the cold & snow,
turn off my freezer, and save some electricity money 😀
Can use that electricity for my Class A amps instead.

Regards
lineup
 
#33
Hi Carlos

I think I too was overly critical of JLH's 70's circuit, but lineup has correctly pointed out that things have moved on - and I would say tremendously in the last decade, even since Self published his "distortion" series in EWW.

Yes you should be able to use a BC640, but whenever a smaller transistor is being asked to do the job of a bigger one I recommend fitting a heatsink. Was it Cray who said no semiconductor should ever get over 55 C? I'm sure there are many TO-92 clips around, or glue to aluminium plate.

I note you've used a fast output transistor. The circuit I posted works well with slower 2N3055/MJ2955's (meaning the 3...4 MHz-ish types) but for 70W you can use MJ15003/4 with BD139/140's (and 640's) from rails up to +/-45 V. (or MJ21193/4) 🙂

Faster devices are more difficult to handle, and if you use them in that circuit it may oscillate ... 😕

cheers
John
 
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