Instructables

how to increase W of audio output ?

Hello , i have a amp with output ~0.5W . I want to make a simple circuit to get a higher output (1w or higher).
Please tell me what part i need and how i do it .
Thanks!

sorry for my bad English :(

Without knowing the specifics of your amp (a small, previous request), but looking at your previous posts, I am going to base my reply on the LM386 / Little Gem amplifier.

Referencing your next question and the picture you posted there, remove the 220 uF capacitor and the 25 ohm pot (lug 3) and insert the circuit shown here. You can run both circuits off of the 12 volts required by the additional amp, in other words, change the 9v on your LM386 amp to 12v and tie the power to the other amp.

The only thing you might need to do is place another resistor in line (in series) with P1, between C1 and P1, probably somewhere between 10K ohm and 100K ohm, in order to reduce the input enough to not overload the new amp. The best way to determine what you need is to put a 100K ohm potentiometer in between C1 and P1 with the lug closest to P1 tied to the the center lug. Start with the resistance between those 2 lugs at 0 ohms. Then set P1 so that upper lug and the center lug are at 0 ohms (max volume for the amp). Turn the gain down on the LM386 amp and start playing music through it. Turn the gain up on the LM386 amp and listen for distortion. If you start to get distortion before you get to the end of your gain rotation, you need more resistance in front of the "test potentiometer" on the second amp. Place another 100K ohm resistor in front of it (after C1) and try again. Once you can get all the gain out of the LM386 without distortion, then start turning the "test potentiometer" until you get the sound you want for full volume. Measure the resistance between C1 and the center wiper on the "test potentiometer" and use the next closest standard value resistor under that reading.

You should be good to go after that, as long as your speaker(s) can handle the power (up to 4 W).

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gmoon2 years ago
I know this has already been answered, but since we know your amp uses a 386 (from your other question), the easiest way to get 1 watt is to make a "bridged" version from two 386 chips, like the little gem MkII.

Note that doubling the output wattage doesn't make an amp twice as loud. Loudness is logarithmic, which in this case means twice as loud as 1/2 watt is 5 watts...
login721 (author) 2 years ago
Thank a lot... :)
i will try it tomorow.
In order to help you, we (the community of answerers) need to know more about the amp that you have. Preferably a schematic of it or at least a link to where you obtained it. If you can do so, I'll do my best to help.

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login721 (author)  Quercus austrina2 years ago
Hello, thanks for reply my question .
I dont want to modify the amp, i just want to add a circuit between the amp and speaker to get louder sound.
Thanks!
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Your magic circuit is called (drum-roll...) an amplifier! You could use a power amplifier as good stereo equipment does - there is a pre-amplifier select (different inputs) and condition (bass, treble, loudness) the signal with only a few watts output and an power-amplifier to make the small signal LOUD!

So, you can add another amplifier, or maybe, just maybe modify your existing amp. But for that, you will have to get a schematics and good understanding of the circuit.

And anyway: If you go from 0.5W to 1W (factor 2), the sound is _not_ twice as loud!
To make the sound twice as loud, as a rule of thumb, you will have to go from 0.5W to 5W (factor 10). That's how our ears work.

Annoying for electronic engineers, but that way we can hear the whisper of the wind (µW) but still withstand the sound of a disco (kW).

And of course, as sshuggi says, the speakers will have to stand the higher power.
The problem is.... We need to know more about amp and speakers as far as their design limitations. Sure, you can amplify the signal, no problem. But, if those speakers were meant to only operate at the 0.5W that you amp outputs, then giving it 1W could fry it. This is more than likely true if they came as a pair. Think of it like this. Why put 100W speakers with a 0.5W amp? You don't, you would waste money. Engineers will design very near the limits of their system to get the most out of it at the cheapest price.

If you have the make and model of the speaker, you can probably find the datasheet for it online. This will tell you the maximum rated power output. This will tell us how much it can be amplified, or if it can even handle more.