Graphic equaliser

Our good friends at Adafruit put this project on their Learning System earlier this month. It’s a beaut: you’ll learn something making it, and it looks fantastic when set up. Before we get into the nitty gritty, here’s some video:

This graphic equaliser (a spectrum analys/zer if you’re from the USA) is made from a RGB led strip, with everything down to the audio processing run on the Pi. Everything you see in the video is happening in real time. The setup runs Python, and is based on LightShowPi (which was originally designed to orchestrate Christmas lights), so you’ll be able add LightShowPi features like SMS control from your phone if you’re an advanced user.

Some soldering is required – but soldering is easy, and this is a good project to earn your soldering wings on if you haven’t already. There’s the usual full and helpful tutorial over at Adafruit, along with tips, a parts list, code and all that good stuff. I wish I’d had one of these for my student bedroom. Imagine the parties!


George Brooke avatar

first!!! got here 23 secs after it was made

The Raspberry Pi Guy avatar

They are very cool – I included one in my ‘Two years of Pi’ video!

Soldering is fun – as long as you don’t have a Gordon on standby ;-)


liz avatar

Dr Buzzkill Hollingworth. We keep him around to remind us never to have to much fun. ;)

The Raspberry Pi Guy avatar

I smell a deed poll!

David R avatar


Sorry, once a teacher….

Michael Hunt avatar

This is very cool. Yes, a ‘spectrum analyzer’ because for us a ‘graphics equalizer’ is a tool to adjust the gain on different frequency bands in the audio spectrum. What do you call that?

Advert warning:
AdaFruit has become my ‘go to’ supplier for parts. They have fair prices and provide excellent tutorials and support to the make/build community.

Wouter avatar

I’m curious too. I don’t know anyone who would call something an equilizer that was just spectrum visualization without spectrum control. Any british folk willing to help?

Andy avatar

Wondered about that, too – I’m a Brit, but for me an analyser just shows me what’s there, an equalizer has knobs to adjust things

Mark avatar

Yes, this is a spectrum analyser (always spelt with an “s” on this side of the pond, unlike ise/ize).

A graphic equalizer is a set of sliders controlling band-pass filters, such that the positions of the sliders “looks like” the frequency response. Some units, popular in the 1980s, combined the two functions with the sliders next to the displays.

Dennis Williamson avatar

Kind of an expensive project! $125 just for the LEDs. Also, the materials list in the instructions says “15 ft (1m)”, but it should say “5m”.

Anders avatar

Looking really cool! I wonder if it would be possible to implement this to listen to Subsonic playing FLAC-files.

Chorlton avatar

Very expensive spectrum analyser but good to read through the steps even if it’s out of my price range.

Strange that the UK suppliers charge *much* more than the USD price on the Adafruit website, even accounting for costs of transit.

Will someone please sell the PlotClock kit and write some Python code for it? :)

Stewart Watkiss avatar

Looks great. I was looking for some code that could do the same from a sound input (eg. USB sound card and microphone). I took a look at the code and see that the code the FFT sampling is based upon is discussed here: Which is even closer to what I was looking for. It’s interesting to see how the code has developed, showing the community spirit of the Raspberry Pi community and the benefit of collaboration and open source software.

Now to take the same code and modify it for my project as well.

The LED matrix provides a smaller display, but may help bring this into other peoples price range.

AndrewS avatar

Oooh, surprised to hear that it isn’t using

I dunno much about FFTs, but I wonder what improvements using GPU_FFT would be able to offer?

Neil avatar

The update rate looks fast enough for the eye, so about the only benefit would be moving number crunching off the ARM and onto the VideoCore.

Juski avatar

Graphic equaliser? Nah. It’s definitely a spectrum analyser (or spectrum analyzer for USA resident folks).

Graphic equalisers are for making adjustments of audio signals, boosting or attenuating ranges of frequencies within certain bands.

A spectrum analyser shows the amplitude of audio signals within certain frequency bands.

Neil avatar

In general, spectrum analysers can operate at any frequency, depending on which specific one you buy. Some cover the audio band, many more (actually, most of them) cover the radio frequencies up into the many GHz.

To add to the confusion, more recent FFT-based low-frequency spectrum analysers are called Dynamic Signal Analysers, and typically cover the range from a few hundred micro-Hertz to around 100kHz.

Blaise Bernier avatar

I’m a touring professional live sound engineer and I want to fix a common mistake that I see everywhere on the internet. This is a spectrum analyser (as unprecise as it is) and NOT an equalizer. An equalizer (EQ for short) is a group of audio filters to shape/correct/modify an audio signal and not a visual gizmo.

The thing looks cool though ;)

Jim S avatar

Cool indeed. One of my favorite scenes in any movie is the “jam session” between the mothership and the ufo hunters in Close Encounters. I wonder if anyone has tried to do a display like that….

Scott Driscoll avatar

I made this before the GPU code came out. It’s barely able to do everything in real-time in python, although the bottle neck is more just moving data around rather than the FFT. Yes it’s a spectrum analyzer but everyone calls it a graphic analyzer, so the title of this post might be better for telling people what they’re clicking on.

jacques avatar

yay a easy project im going to do wil be my first with the raspberry pi

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