Hi , can we use an LED driver as power supplies for amplifiers such as LM386? Its 12v 2A and very cheap( 1 dollar) compared to a DIY one whose transformer alone costs ₹200 ( 3 dollar) . If we can use them, do we need to add extra filter capacitor near the amplifier?.
It depends on the driver. Most of them are just switching supplies with PWM capability on the output. Post a like to the driver. The LM386 requires little power though and runs on a wide variety of voltages. What about just using a spare power adapter from some broken device?
Can you post a picture? The ones I have seen have an adjustment for voltage and current limit. As long as the output isn't PWM, then it should be fine. If the output is PWM, then you'd need to add a hefty filter capacitor to smooth it out. Which may confuse the supply as it won't be expecting to drive a capacitive load.
12V is too high to power an LM386 unless the speaker is 16 ohms because the LM386 will become too hot. The datasheet shows that with an 8 ohm speaker the heating increases when the supply is more than 9V but the maximum output power stays almost the same.