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Topic: Need a simple audio amplifier (Read 76380 times) previous topic - next topic


If you need better quality than a single-transistor switch, and more power than an LM386, you might as well buy an amplifier module or "powered speaker" from one of the import vendors...


Its good to see the responses. Thanks for that. However i've decided to step away for a few days to "chill out", so i might not respond for a few days. But at least i owe you a response...

Perhaps the lm386 is the solution. I don't know. I've tried with the tda7052a (which i heard is a similar amp ic with internal caps) and that didn't solve the 'starvation' issue. With 'starvation' i mean that so much current goes from the battery to the little speaker that my display backlight and led indicators are dimmed. In fact, seen on a scope, it pulls the 5v below 2.8v at which my 328p is saying "no more, i'm off..". I know the circuit is otherwise fine because if i disconnect a single lead from the speaker everything works as it should.

The phone works on a 1400 mAh battery pack and now uses only 45mA on idle. The sound wave is a full 0-5v square wave generated by the Arduino tone() function.

The speaker is very small. It is the original 'handsfree' speaker of the phone that has been in there since the 90's and should be able to provide sufficient noise. Since it mounts in the plastic handset i'm not keen on replacing it.

My feeling is that it should at least make as much noise as a little piezo speaker. That is, i should hear it ringing across the room.


Piezos can be remarkably efficient and loud when driven around their resonant frequency.

The TDA7052A is a bridge amplifier, which means you can't ground either side of the speaker. Also, if you forget the capacitor between the Arduino and the TDA7052A, it may drive the output hard one way. Causing no sound, but a lot of current. And you still need a volume control.
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So far I've already played around with the pitches.h library and hooked up a small 8ohm 0.1w speaker directly to the arduino (using a 150ohm resistor too)  So far that has worked fine with my program.

But my goal for part of my project is to hook up a larger more powerful speaker (I have a 4" 8ohm 10w or a 2" 8ohm 3w speaker that I'd prefer to use) and get loud audio (simple tones really).  So, I need some kind of amplifier.   

I've started to search around the forum and on google but I just get more confused as I look at amp circuits.  I tried making the audio amplifier from the Aduino Basic Connections guide http://arduino.cc/forum/index.php/topic,154549.0.html

Although I didn't have a BC337 on hand.  I used a P2N2222 instead.  (I also have some BC328, BC549, and BC550 lying around)  I did get some audio out of the speaker, but it isn't what I'd call loud.

I also tried making this: (found it searching google)

but that was even worse, as I didn't get any audio from the speaker.

Poking around I do see CrossRoad's circuit using IRF3707Z MOSFET http://arduino.cc/forum/index.php/topic,157647.msg1184322.html#msg1184322, but I'd have to order one (would prefer to use components I already have if possible).

I also see this post http://arduino.cc/forum/index.php/topic,114094.msg858503.html#msg858503

but there is no guidance on what values are needed for the resistors and capacitors.  I would try making it, but what components do I use? (I have a fairly good assortment of resistors/capacitors and the 4 transistor types I mentioned)  I'll also be powering my project from a 12v battery, so would prefer to use that as the voltage level for the speaker (but could just as easily step it down, since I have a 12v-5v switching voltage regulator)

Looking for help  XD

Which software do you use in making all those layout circuits?

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