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IC Recommendations? LED Audio Spectrum Analyzer Project

Alex Hogen
Prodigy 105 points
Other Parts Discussed in Thread: TL072

Hi there!

First off: I have a little experience with electronics, but not a ton. That's why I'm asking questions before I start this project. :-)

Currently I am trying to plan out how I'm going to build an LED Audio Spectrum Analyzer. I'm hoping to use an IC to split an audio signal into about 10 frequency bands. The frequencies would probably be selected by specific capacitor values, of course.


Then I think I could hook up each band (probably have to be amplified with an NPN or something) to something like the LM3916 to drive 10-16 LEDs per frequency band.


My biggest question is what IC(s) to use to split the audio. I've been looking around and seen things like the BA3812L, the LA3600, or the TA7796Z. All follow essentially the same concept of minimal external circutry to select frequencies. I've also looked at the MSGEQ7, but the 5 freqs are preset it looks like, so I couldn't really make a 10-band out of that.


I don't know if any of you have some experience in this area and have a favorite chip to recommend. I couldn't find anything from TI, but I might have missed something.

Thanks in advance for sharing your knowledge. :-)

  • 0
    TI__Guru**** 189399 points

    Hi, Alex,

    Welcome to e2e, and thanks for your interest in our products!

    This sounds like a really fun project! Maybe one of the community members can share their ideas with you.

    In the meanwhile, I will leave you with this article written by my colleague on a somewhat related topic.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 105 points

    Hi, Don,


    Thanks!

    Again since I'm new to this, I have lots of questions...

    Wouldn't it be much harder to filter an audio signal if it's been run through a rectifier? Especially if you have a filtering/smoothing capacitor tacked on to the end. Maybe I missed something, but I didn't see anything in that article about filtering the input signal and splitting it into separate frequencies for the LED visualizer.

    I just made this diagram to better explain my project idea. I threw in the BA3812L just as an example IC. I don't know if I should be using that one or if there's a better idea out there.

    And isn't TI's LM3916 essentially just a specialized ADC chip?

    I'd love to learn more, so if anybody's got ideas on this, please let me know.

    Thanks!

    - Alex

  • 0 in reply to Alex Hogen
    Expert 1720 points

    Hi Alex,

    I like your idea. I also want to build Audio spectrum analyser. I found this project, which is very similar to yours: http://sound.westhost.com/project136.htm

    It use operational amplifiers TL072 for filters. If it is possible to integrate more filters to the one IC it will be great improvement. There also exist Japanese project of Radio spectrum and audio spectrum analyser, but it doesn't have resolution of complete audio band. Analysis is made by FFT in software. Project is here: http://elm-chan.org/works/akilcd/report_e.html

    LM3916 is precise voltage divider with 10 comparators. It is similar to ADC but with totally different output.

  • 0 in reply to Pavel Ruzicka
    Prodigy 105 points

    Hey, Pavel!


    I took a look at that article. That was very insightful. Essentially I'm trying to make a simpler, smaller version of that. By the looks of that project, it'd be worth putting a rectifier after each filter and before each LED driver.

    I believe the BA3812L is probably going to be a big improvement with the filter network, seeing  as you would only need a simple external RC setup for frequency selection of each band. If you set two of these 5-band EQ chips next to each other, you've got a nice 10-band EQ filter setup.


    I did check TI's supplies, but it seems that they only have digital filters, like the DF1704E which wouldn't work very well for this application, I think...

    Does this whole idea seem feasible to you guys?