Speakers are supposed to make noises. That's what they're for.
Steve
Speakers are supposed to make noises. That's what they're for.
No... In engineering or audio terminology, noise is unwanted sound. There is always some noise (hum or hiss from an amplifier, etc.), and there is something called signal-to-noise ratio. You can get buzzing or rattling noises if you over-drive a speaker, or if the speaker is "blown".
The music from your stereo isn't noise, but the music from your neighbor's stereo might be considered noise. 
Distortion is another kind of unwanted sound. Again, there is always some distortion and the distortion gets worse if you try to get 150 Watts out of a 100W amplifier.
A transistor or two in a (non-linear) switching configuration will also distort badly although the proper use of high-frequency PWM might minimize that distortion. "Class D" amplifiers use a kind of PWM in a controlled negative-feedback circuit (similar to a switching voltage regulator and they are capable of high-quality audio.
I made it but it still makes noises.
The only way you're going to find-out where the problem is, is to switch something around. Plug the Arduino into your stereo.
Or plug your transistor circuit into your computer or phone and play some music... Then, you're gonna' find out what a bad amplifier you've built!!!
I made it but the speaker makes noises
omg, sorry guys. I dont know what happend with my browser of internet, and when i type a reply it doesnt show, and also your replies doesnt show, all of this replies :
Hardizzer:
I made it but the speaker makes noises
Hardizzer:
I have 47nF, will it work ?
Hardizzer:
I think I got it but I dont habe 1.5nF, I have 47nF. Will it work ?
is for the RC low pass circuit you suggested, when I tried that RC low pass circuit the speaker made noises.
Sorry again.
I will try what you said.
DVDdoug:
But that won't do much with a simple switching-transistor circuit. You'd need a regular-linear amplifier.
Ok, first now i made this amplifier circuit
How to connect this amplifier to arduino ? I tried connecting pin 46 on the mega to pin 7 or 3 on the LM386 but as always, the speaker makes only noises.
You need a low pass filter to drive an analog amp like the LM386.
The RC values must be roughly right, so no a 47nF cannot be subsituted for a 1.5nF
Basically 1/RC = 2.pi.f (f = cutoff frequency which needs to be 10kHz or so).
So 10k / 1.5nF will do, as will 1k / 15nF.
You need to set the PWM frequency to the max possible (prescaler = divide-by-1) so
that the PWM is ultrasonic.
What I would do is write a simple program that produces a simple square wave tone: such as https://www.arduino.cc/en/Reference/Tone. Set the frequency to 1000hz. Connect the Arduino pin to the amplifier with a 1k resistor and any capacitor in series, that is:
Arduino ouput -> 1K resistor -> 1uF or greater capacitor (+ side to Arduino) -> amplifier input.
Ensure the Arduino ground (GND) is connected to the amplifier ground. From looking at the amplifier you built, I think GND is connected to pin 4 of the 356 amplifier chip.
At this point you should get some output. If not check the amplifier is working by connecting an audio signal to it, (think headphone jack from a phone or line out from an audio device).
Another question, what power supply is powering the amplifier:
1, is it working and able to deliver enough current?
2. have you used a multi-meter to confirm voltage is there?