I want to build a circuit that shows the real-time frequency components of an audio signal on a number of bar graphs of some sort. Currently, my plan is to build 12 band-pass op-amp filters, and then use a rectifier and RC circuit to create a DC envelope for each output, and then use that signal to drive a LED bargraph or something similar.
The circuit will use a single +3.3V supply, and using 12 band-pass filters is not really negotiable. If I want a 12-channel bar graph, am I stuck using 12 bar-graph LEDs and bar-graph LED Driver pairs? That comes out to $45! Is there a better/less expensive/simpler method of getting a similar result? Ideally, I would not need a microcontroller.