Speakers

What are speakers? You might say they're the ones from where the sound comes. Quite right. In technical terms, it is a transducer which converts electrical signals into their equivalent acoustic (mechanical waves) signals. This waves are produced by a diaphragm which moves back and fourth. There is a coil connected with diaphragm. In this way, it acts as a electromagnet and when current is passed through it, it moves back and fourth. So when we pass a signal of audio frequency, the speaker produces mechanical wave (or vibration) which is equivalent to the electric signal.

Cross section of a speaker

That's the basic of how speakers work. Now there are many type of different speakers. But regardless of its type, all do the same work : produce audible sound according to the electric signal fed.

Speakers can be classified in mainly ways : According to frequency they can work on and according to their impedance.

(1)According to frequency, there are three types: Woofers,mid-range and tweeters. Woofers work on low frequency audio signal. Mid-range are good for medium frequency and tweeters are good for high frequency audio signals.

Woofer

Mid-range

Tweeter

(2)Each speaker has impedance. It can be 32 ohm, 16 ohm, 8 ohm, and 4 ohm. 32 ohm speakers are generally used in headphones. 16 ohm speakers are used in telephones etc. 8 ohm speakers are used in general purpose music systems like the one we use in our home. And 4 0hm speakers are used in loudspeakers where loudness is required.

To drive the speakers, an adequate signal is required in terms of the power. We have to amplify the weak signals to be able to drive the speakers. That's where audio amplifiers are used.

6W class A Audio Amplifier

When I have nothing to do, I like to listen to songs, so for long time I wanted to make my own audio amplifier that can drive two 4 ohm speakers(i.e. stereo). I wanted it to be compact so I was in search of suiatable IC that has stereo amplifier and able to be driven from PC sound o/p or mp3 player o/p. I ended with the IC known as TPA 1517 from Texas Instruments. This is a 6 W stereo audio amplifier IC and requires very less external components. It can be driven from power supply ranging from 9-18 v. The circuit diagram from the datasheet is as shown below.

For more information on the IC and its internal construction, download datasheet from here.

All you have to do is just join the circuit and enjoy the amplifier. I have made it and tested it with my two 4 ohm speakers. Its quality is quite good. It can be driven from the PC as well as mobile phone (with 3.5 mm jack output) and also from TV's audio out pins. One more thing is that use only regulated power supply otherwise it would produce a annoying background humming sound. I used my variable regulated power supply made using LM 317 IC. You can supply voltage to be between 9v to 18v. I used RCA female jack for both input and output. Although volume control is not shown in the circuit diagram you can add volume control just by adding two 10k potentiometers in two input channels as shown in figure below. Repeat this for the second channel.


This amplifier is quite easy to build and very compact. I have mounted it in a visiting card box with input and output female jacks taken out. To connect supply, I have used a 3 pin circuit board mounted header.

So what are you waiting for? Just make it and enjoy your favourite music.

If you have any doubts or problem making this thing or have anything to say to me then write a comment or mail me at dmehta17@gmail.com.