In my application I play sound clips from the ISD1700 series soundcard. Before I started this amplifier add-on, I tried to hook earphones directly to pin 13 and 15 to the chip to hear sound from the on-board sound port. The volume is acceptable, but when I used an 8-ohm speaker, the volume is low, however I configured the chip to run at max volume and to ignore the VOL pin.
I read up in their manual that one can attach a transistor to amplify the sound, but I want to make loud sound that can be heard from the other end of the room.
I first tried connecting earphones directly to AUD/AUX pin of the soundchip in series with a 22uF capacitor and the sound volume was so low I could almost not understand it.
So I pull out my LM386 amplifier because it has amplified radio signals for me in the past and I tried it with the analog output of the sound chip as shown above, and even though the amplifier amplified the sound somewhat, it seems to still be at lower volume than what I could get if I hooked up the earphone directly to pins 13 and 15 of the soundchip.
I'm afraid if I hooked the output of pin 13 or 15 to the amplifier input, I might blow something up.
Now during tests, if I remove the resistor and disconnect pin 17 from the amplifier then as I hold the wire I hear a loud buzz which suggests to me the LM386 knows how to amplify faint sound.
Is there something I can do to improve volume of the sound using the same kind of circuit? I'm willing to add more commands through the SPI interface if that makes the world a difference.
P.S. the coupling capacitors I use is 0.047uF and I intentionally not connected anything to other parts of the ISD soundchip as they weren't relevant to the question.
Now when I did testing, I used a breadboard for the amplifier part of the circuit. The soundchip section is all on PCB. and the power supply I used is 5VDC