• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

V76

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Dave P

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Joined 2005
#1
I have made a V76 type mic pre with a White follower output stage. (2x EF86, 1x12BH7). I have basically copied the first stage of a V76. There are 2 problems I need help with as Iv'e been working on this for months and I need fresh ideas! First problem is a very low frequency (about 2Hz) on the output which unless I have a 2k resistor across output ,spoils the 90dB S/N ratio. second problem is that the Bass rolls off from 100Hz to about 3/4 of 1KHz value by about 40Hz. Otherwise frequency response is flat to 35KHz.

By the way, I have translated from the telefunken braunbuch the technical descriptions for the V72,V77 & V78 circuits. I would be happy to place them somewhere accessible for members but I don't know how, this is my first ever post!

all the best
Dave P
 
#9
Now I know what my EF804s were for! The screening on the mains transformer is to protect other circuitry from the extraneous field it generates, not to protect the mains transformer.

I await diagrams with interest.
 
#10
Thats right, this is one of the reasons why they managed to obtain such amazing S/N ratios (~120dB). Although the tubes are not canned, the steel chassis wraps around the tubes quite closely as well. The Mains TX screening stops the mic TX picking up hum in such a confined space, the components are really packed in.
Dave P
 
#11
It seems that money was not a problem for people building and buying V76s and such back then. Did you ever see the input transformer? Also, all the metal is expensive mumetal including the amplifier case and covers, as well as all the transformers shields. The input transformer has very big cobalt-core (permendur) and a nice 10 layer copper/mumetal shield and had also 10 section bobbins!!! I don´t know anything even close to this type of engeneering at any time.
 
#12
EC8010 said:
Now I know what my EF804s were for! The screening on the mains transformer is to protect other circuitry from the extraneous field it generates, not to protect the mains transformer.

I await diagrams with interest.
Click to expand...

Hello ,
here are the links to nearly all "Braunbücher" and a link to the Klangfilm amps .


http://www.kubarth.com/


http://www.irt.de/IRT/home/indexpublic.htm

http://klangfilm.free.fr/index.php?lng=0&music=&type=0&frame=0&item=&title=&dir=&num=

And here is a picture from a friends mixing console with a TFK M5b .

Telefunken made many descriptions , like their tube data books , in both languages , english and german .
Regards , Alexander .

An externally hosted image should be here but it was not working when we last tested it.
 
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