About audio's volume

Hi all
I have a speaker ( 3W-8 Ohm )
I do a simple circut to play some tones with it, but I find volume is low, I want to ask how to adjust it's volume same as my radio cassete ? ( I think I will need a variable resistor ) , I dont know how to do
Thanks for reading

I do a simple circut to play some tones with it...

That's awfully vague... Do you have an amplifier circuit?

Do NOT connect a speaker (or headphones) directly to the Arduino. The minimum load impedance is about 125 Ohms. If you connect an 8-Ohm speaker you can damage the Arduino (and you won't get much sound).

...to adjust it's volume same as my radio cassete ?

How loud is your cassette? Does it have a similar sized speaker?

( I think I will need a variable resistor )

You probably need more than that. In the right amplifier circuit, an different (or variable) resistor (i.e. a potentiometer or "pot") can give you more gain, but usually a pot is used to reduce volume.

You need an amplifier. I've got [u]this amplifier[/u] driving a couple of small speakers in my bedroom. (This particular amp doesn't come with a power supply and you have to buy the wall wart separately.)

If you want to build an amplifier, look for an "audio power amplifier" chip. The LM386 is popular and easy to use, but you won't get 3 watts out of it (and you may not need 3 watts).

DVDdoug:
That's awfully vague... Do you have an amplifier circuit?

I haven't bought any amplifer circuit

DVDdoug:
You need an amplifier.

yes, thanks for you advice, I will buy one

Computer speakers have an inbuild amplifier, and a volume control.
Leo..