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I am making a sound amplifier using LM386 and 8 ohm speaker. Can anyone tell me which IC is most suitable and how to convert 220V to 9V to operate the circuit without transormer?

Renan
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Sunny
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    A transformer is by far the best way to get isolation at these power levels. Without isolation the whole amp could be live and dangerous. Go buy a power supply. Your not at the level where you should be messing with lethal voltages. – Olin Lathrop Oct 30 '12 at 14:36
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    Why do you not wish to use a transformer? – Brian Carlton Oct 30 '12 at 18:08
  • If you are amplifying a sound, what is the source of the sound signal? Not using a transformer will mean that your device will be directly connected to mains through your amplifier. If it has a metal housing, then chances are that the whole housing will be live. Same goes for the antenna or other wiring coming from it. – jippie Oct 31 '12 at 07:46

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Use a switched mode power supply. They come in a a small and very light weight wall wart form factor, are cheap, easy to use, safe to operate and many people have one lying around from an old mobile phone charger.

Any other transformerless solution is possible, but can be potentially lethal; one should really respect those tiny little innocent-looking copper wires that come from a wall socket. With 1 rep and an empty profile, I don't feel confident I should explain you how to do a transformerless design, but maybe someone else is more fearless.

jippie
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If you understand the risks, you can look for a transformerless power supply, like the ones described in this Microchip application note, which provides a large amount of example designs.

However, quoting from the very same appnote:

Warning: An electrocution hazard exists during experimentation with transformerless circuits that interface to wall power. There is no transformer for power-line isolation in the following circuits, so the user must be very careful and assess the risks from line-transients in the user’s application. An isolation transformer should be used when probing the following circuits.

Also, this answer recommends against using such types of power supplies unless you really know what you're doing:

I don't mean to be harsh, but the cost of an isolated, safe, ready-made, efficient, nicely packaged wall wart is absolutely negligible compared with the medical bills associated with electrocution, which is itself negligible compared to the costs associated with being sued for causing electrocution if you're selling/distributing this thing.

Since I don't know how good your skills are, I would just go with a wall-wart (likely you have an unused one laying around) or a transformer and be done with it, mostly due to the isolation that can prevent you from being exposed to lethal voltages.

Community
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Renan
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    Actually with really good electrocution, medical bills aren't that high, just some funeral expenses perhaps. If the point is economy, then make sure to not go half way. Good isolation is still the cheapest, but without isolation you should go all out. Use a conductive case, tie it directly to the hot side, recommend it be used on a wet floor with bare feet, etc. – Olin Lathrop Oct 31 '12 at 00:05
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You are looking for an off-line power supply, here is a switching version. there are versions that use capacitors but they cannot supply very much power. They are non-isolated and have lethal voltages on board so you cannot plug them into other electronics and you probably should pot them in epoxy for safety.

placeholder
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    Sunny wants to make an audio amplifier. He would have to isolate no just the amplifier, but also the speaker *and the audio source*, unless he couples that with an audio transformer... – Wouter van Ooijen Oct 30 '12 at 14:56
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    but an audio transformer is insufficient to withstand mains voltages so even that is not recommended. – placeholder Oct 30 '12 at 15:21