Hi, I'm working on a VUmeter around an ARM uC. I would like to read audio signal with an ADC input of the uC.
As the ouput of mp3 portable player or cell phones is too low compared with the 3.3V ADC input I want to add a simple amplifier.
I'm working on this schematic:
My questions are:
- What is the amplitud signal (typical) for a portable device?
- What is the max gain that could obtain from that kind of amplifier taking into account that I want 0-20KHz?
- Could I use a variable resistor instead of R11 to adjust the gain?
- Is there another better circuit for that purpose?
Thank in advance!