I amplify using LM358 Op-amp and 2 resistors.
I played a song on my mobile. The output of the Mobile is the input of my circuit.
The output of my circuit is connected to 8 ohm speaker.
I hear unclear drums, Low volume and I can not hear the singer.
I tried to change the gain 101 , 50 , 10 and 2.2 but It gives almost the same result.
Is it possible to make the volume higher with not too bad quality?
What about using transistors ( common emitter for example ) is it better that LM358 ?
Best Answer
An LM358 is a really, really bad choice for driving an 8 ohm speaker. Typical output current is 40mA and into an 8 ohm load, the power delivered will be: -
\$I^2R = 0.04^2\times 8 = 12.8 mW\$
Also, you may have wired up your stereo inputs incorrectly and be cancelling out the mono part of the stereo signal - this tends to cancel most vocals, bass etc. i.e. anything that is centred in the stereo field.
Try using an LM386N-3 - it is capable of outputting 500 mW. You could do it with discrete transistors but I don't feel you are ready for this step just yet.