amplifier circuit

[black_viper950]

hello, im building a low cost amplifier for my mp3.. can you please help me if this circuit is suitable? also, what is the suitable ac voltage for audio in? i've done some researched and found out that typical mp3s have 200mV. is that going to be my input ac voltage? how bout my frequency? so sorry, i've just started basic electronics couple of weeks.. thanks!

here's the link
**broken link removed**

 

[MikeMl]

Have you found some 25 Ohm speakers? Most are 4 or 8 Ohms.

For stereo, you will need two amplifiers.

Have you looked at the several stereo audio amp ICs made by **broken link removed**. and others?

When I wanted a booster amps/stereo speakers for an MP3, I bought a set of Powered Bose computer speakers at a garage sale for $0.50. They run off a 12Vdc Wall-Wart, so I am able to run them in my RV off battery power. They work with a DVD player, too.

 

[black_viper950]

not really, but i think 8Ω is ok but with lower volume.. um actually, i just want to use discrete elements for making a mono speaker, no ic's. i am really confused about the "audio in".. please help :/

 

[MikeMl]

The "audio in" comes from whatever you want. I don't know what level it will take to drive the amplifier to full output, but "line level" from an MP3 is likely to be about right. Take either the Right or Left channel from a stereo plug; tip and sleeve, or ring and sleeve, where sleeve is grounded...

 

[black_viper950]

i see but, what about the frequency of the input? how much Hz is it usually?

 

[MikeMl]

i see but, what about the frequency of the input? how much Hz is it usually?

Music is usually 20Hz to 20,000 Hz, while spoken voice is like 200 to 5,000 Hz.

The amplifier as drawn will likely pass 50Hz to ~50KHz, the crummy little speaker will be lucky to reproduce 300 to 3000Hz.

 

[audioguru]

The low cost amplifier is too simple so it will have poor performance.
Its power into a 25 ohm earphone is only 0.25W and its distortion will be high.

An IC amplifier will have much better performance, much less distortion and more power into a normal 8 ohm speaker.

 

[black_viper950]

aww, i see.. im really new to this stuff actually. so, how do you exactly lessen the distortion of the output signal? do you need to increase the stage of the amplifier?(if you're using dicrete components).. btw, i still dont know how an ic operates.. and what exactly is line level? peace

 

[audioguru]

A half-decent IC power amplifier has about 15 transistors. It has a lot of open-loop gain so when negative feedback is applied (many IC amplifiers already have negative feedback) then the gain is reduced to a useable amount and the distortion is reduced to become almost nothing. It can drive a low impedance speaker so that the power is fairly high when the supply voltage is fairly low.

Line level is the signal from a radio tuner, CD player or MP3 player which is a level of about 100mV to 600mV RMS.

 

[Fitz Gabby]

The circuit of figure (see link) shows an ideal amplifier
fed into its input through a voltage source
continuous. The components are C = 12 F, R1 = 1.2 kohm and
R2 = 6 kohm. The switch is closed and when the circuit reaches the
steady, the voltage Vo in volts, it is

the answer is -7.5 v. I need calcs
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**broken link removed**

 

[audioguru]

Fitz Gabby,
Your link is for a Home Page where there are hundreds of questions. Which one is yours?