I assembled velleman Tr8040 amplifier for my college project and is working well, but the thing is that i can’t understand the circuit diagram as i have to explain to the tutors, can any one pls explain how it works and also i need a clear circuit diagram. I am planning to add a tone control circuit aaroncake.net/circuits/tone.asp to the amplifier i need help of how to connect both the cicuits pls help!! Thanks
We can’t provide circuit descriptions.
hello, i don’t unserstand the problem 
the K8040 use a TDA7293 you can found this data sheet on the web.
Is a integrated IC so it’s work like every amplifier. you should found some projet whit 2n3055 for anderstand the principe of an amplifier.
second : to connect your tune controler, no problemo. connect the output of J2 or J3 to the imput of amplifier k8040.
You have a mono sound, for steréo sound you may have two k8040.
(or put two resistor 47K between J2 and j3 and pick up the output in the middle of this resistor for have a mono sound whit the two channel, or best : aaroncake.net/circuits/mixer1.asp whit in1 et in2 are left and right channel 
)
somes tips :
The notice of K8040 : designnotes.com/downloads/K8 … nglish.pdf
here my personal documentations (in french)
adn56.free.fr/DOCSelec/electroni … 0audio.htm
adn56.free.fr/DOCSelec/electroni … A_data.pdf
adn56.free.fr/DOCSelec/electroni … audio.html
regards. (sorry for my english, i’m french and i never realy learn english ^^)