Was debating whether this should be here or audio so please move if appropriate.
I am trying to amplify some sound up to a relatively high volume, IE, you'd have to talk loudly to talk over it sort of volume.
I believed an LM386 would be appropriate for this, however I don't seem to be able to get the volume quite high enough.
The speaker is an 80W, 8Ohm speaker.
I am using the reference diagram from TI here: http://www.ti.com/lit/ds/symlink/lm386.pdf
I've attempted the gain = 20 and gain = 200 examples, but both yield a peak output around ~60mA at 12v.
I'm a little confused as to how and why this is? Applying ohms law, shouldn't the current output be around 1.5A?
If possible, running the amplifier at 3.3v would be very useful so as not to have to implement a 12v Dc-Dc converter, but that's a somewhat different question.
I'm no audio expert, but I think you're expecting a higher output power than the part is capable of.
If you look at the performance graphs or the table on page 2, both imply a maximum output power of around 700mW.
You're reporting it outputting 60mA - 60mA * 12 V = 720mW, which sounds like it's doing just what it's supposed to.
The LM386N-4 is rated for 1000mW (1 Watt). The other versions are rated lower. With a single 12V power supply you can get 12V peak-to-peak. That's about 4.25V RMS. That's a little more than 2W into 8 Ohms. That's theoretical... In the real world there will be some voltage drop across the amplifier and you'll get less.
You'll need a higher power amplifier, and more voltage or lower impedance.* A bridge amplifier design can provide double the voltage for 4 times the power.
The efficiency of the speaker makes a difference. A horn type speaker can go quite loud with a couple of watts.
If possible, running the amplifier at 3.3v would be very useful so as not to have to implement a 12v Dc-Dc converter
Don't forget that if you use a DC-DC converter, your 3.3V power supply has to supply all of the power (wattage) to the speaker.
*This is why car stereos use 4-Ohm speakers. With a 4-Ohm speaker and a bridge amplifier you can get about 20W from a 12V car battery (which is actually 14.4V). Higher power car amps use DC-DC converters and some really-high power car stereo amps can go down to 1 Ohm (Four 4-Ohm speakers in parallel).
Right, thanks.
I'm using an LM386N-1 at the moment, which according to the datasheet only has a typical power output of 325mW.
By dropping in an LM386N-3 or N-4, you believe this should allow me to drive the load at a higher power?