How does one build a Visual Equalizer

[Lennon Norris]

I want to build a visual equalizer for audio as my college project. It should not be a complex one but just a simple one with around 6 to 7 bars. I don’t have knowledge about the physics and mathematics required to create it but there must be some way to make it. Can anybody tell me how do I build it?

[phunsuk]

First of all you need is a LM3914 dot/bar driver to wire 10 LED bar graph in green/red or green/red/yellow format. For multiple bars, one need to build filters for passing an isolated signal to specific frequency of the LM3914 dot/bar driver. But it isn’t as easy as it seems. One has to compute value to get proper capacitor, inductor and resistor frequency values. To transfer signals of low frequency of 4 KHz a DSL filter can be used.

[Vicky Woodley]

The main disadvantage of using LM3914 dot/bar driver is that it limits the signals to linear resistance ladder which is hard to customize. You can wire it yourself to voltage comparators. The voltage scale is up to you. As standard audio signals are of frequency of 1V, an Op-amp running in each of LM3914 can be used. Without it the results will be poor.

[chuck28]

I recommend you to create two voltage following configurations to handle both channels and run them in summer voltage configuration. With the use potentiometer in combination with above mentioned op-amp you can achieve a variation in frequency of Audio signals. For filtering of signals, I suggest you use only capacitors and resistors as they are cheap and give good results.