I made a horn with UM3561 and it have oputput for spiker.Maximum output voltage is 12V. But the problem ist that the horn is to silent. I need an amplifier for that horn and it must have 12V supply voltage.
Here is the shematic for 12V version. http://www.reber.si/zvocni_efekti/UM3561/UM3561-12V.sch-200dpi.gif The spiker is for car alarm and I think that is good, if you mean that. The horn works properly, but it is to silent, so I need a way how to decrease the output signal.
I don't know what is a "spiker". Your schematic shows an 8 ohm speaker. If the sound from the speaker is not loud enough then you need to increase the output signal, not decrease it.
A car horn is very loud. But your circuit feeds a square-wave with a voltage of 13V into 8 ohms which is a power of only 21W peak or only 10.6W average.
If you feed the signal to both ends of the speaker (with one end inverted) then the power will be 4 times more. Then there will not be DC so the speaker will work better. If you use a 4 ohm speaker then the power will be doubled to 80W.
I don't know if the sound generator can drive your 1k base resistor so I increased it and increased the collector resistor.
I mean speaker. I'm doing mistakes, because my english is very bad. So I will do the changes and try it on the protoboard. Will your version work with 4Ohm speaker?
So I must connect the drain of first mosfet to ground and put a speaker between the drain of second mosfet and ground.
No. The drain of the Mosfet is its output in this circuit. You never short an output to ground. Just make the first circuit and hope that the DC in the speaker does not destroy it.