VU meter

45 Articles

Teensy Spectrum Analyzer Has 170 Channels

June 21, 2022 by 14 Comments

While high-fidelity audio has come a long way in the past several decades, a lot of modern stereo equipment is still missing out on some of the old analog meters that were common on amplifiers and receivers of the 60s through the 80s. Things like VU meters don’t tend to be common anymore, but it is possible to build them back in to your sound system with the help of some microcontrollers. [Mark] shows us exactly how to reclaim some of the old-school functionality with this twin audio visualizer display.

Not only does this build include two displays, but the microcontroller is keeping up with 170 channels in real-time in order to drive the display. What’s more impressive is that it’s being done all on a Teensy 4.1. To help manage all of the data and keep the speed as fast as possible it uses external RAM soldered to the board, and a second Teensy audio board is used to do the real time FFT analysis. Most of the channels are sent to the display hosting the spectrum analyzer but two are reserved for left and right stereo VU meters on the second display.

The project from [Mark] is originally based on this software from [DIYLAB] so everything is open-source. While it was originally built for a specific piece of hardware, [Mark] has it set up with a line in and line out plus a microphone input so it can be used for virtually any audio hardware now. For another take on the classic VU meter, take a look at this design based on an Arudino instead.

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VFD Character Display Turned Into Audio VU Meter

March 9, 2022 by 8 Comments

Humans love visualising music, whether it’s in the form of an inscrutable equation drawing squiggles in Winamp, or a simple VU meter pulsing with the beat. This build from [mircemk] is of the latter variety, repurposing a VFD display to do the job.

The project is built around a VFM202MDA vacuum fluorescent display, which provides that lovely green-blue glow we all know and love, driven by a PT6314 driver chip. This has the benefit that it can be readily driven by a microcontroller in much the same way as the familiar HD44780 character LCD driver chip. With some minor tweaks, the character set can be modified to allow the display to become a surprisingly-responsive VU meter.

An Arduino Nano runs the show, with an envelope follower circuit feeding a signal for the left and right channels into the analog inputs of the microcontroller. The Arduino then measures the voltage on those inputs and feeds the necessary commands to the PT6314 driver to update the display.

The resulting VU meter has 38 bars per channel, and is highly responsive. The fast flickering of the meter bars in response to the music make it compelling to watch, and the era-appropriate enclosure the project is built in adds plenty to the aesthetic.

We’ve seen other VU meter builds before too, like this one that uses a little physics knowledge to create a more realistic analog-like needle meter. Video after the break.
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Visualizing Audio With An LCD VU Meter

November 8, 2021 by 6 Comments

We all love seeing data represented in pretty ways — whether it’s necessary or not. Take VU meters for example. They’re a super useful tool for audio editors to balance signals, but they also look really cool, even if you’re only listening to music. Who didn’t use a Winamp skin with a built-in VU meter back in the day? Even after the demise of everyone’s favorite media player, we still see these great graphs popping up all over the place.

Most recently, we’ve seen VU meters circle back around to have a bit of a retro vibe in this awesome Arduino-controlled LCD VU meter built by [mircemk]. Based on the KTAudio VU Meter project, it features an ultra-wide LCD, audio input, and volume knob, all tidily wrapped up in a case whose color scheme that can only conjure images of the famed Altair 8800, or an old Tektronix oscilloscope. The LCD itself is fairly responsive — but you can judge for yourself in the video below. The signature fading that so commonly accompanies screen refreshes on LCDs such as this one really adds to the retro effect.

You may just need one of these displays on your desk — after all, while you may not need to know how loud each audio channel is, don’t you at least want the information available? Just in case. Bar graph display a bit too modern-looking for you? Well then you should check out [mircemk]’s OLED version that displays dual analog meters.

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Improving OLED VU Meters With A Little Physics

August 9, 2021 by 23 Comments

Last month we featured a project that aimed to recreate the iconic mechanical VU meter with an Arduino and a common OLED display. It was cheap and easy to implement, and promised to bring a little retro style to your otherwise thoroughly modern project.

[sjm4306] liked the idea, but thought it was a tad too stiff. So he’s been experimenting with adding some physics to the meter’s virtual needle to better approximate the distinctive lag and overshoot that’s part and parcel of analog indicators. Obviously it’s something that can only be appreciated in motion, so check out the video below for an up-close look at his quasi-retro indicator.

Unfortunately there’s no code for you to play with right now, but [sjm4306] says he’ll release it on the project’s Hackaday.IO page once he’s cleaned things up a bit. We know it will take more than a few wiggling pixels to pry real analog indicators out of some hacker’s tool boxes, but anything that helps improve the digital approximation of this sort of vintage hardware is a win in our book. Continue reading “Improving OLED VU Meters With A Little Physics” →

Analog Style VU Meter With Arduino And OLED Display

July 14, 2021 by 20 Comments

Looking for a digital recreation of the classic analog volume unit (VU) meter? If you’ve got an Arduino, a few passive components, and a SSD1306 OLED, then [mircemk] might have the answer for you. As you can see in the video below, his code turns a handful of cheap parts into an attractive and functional audio display.

The project’s Hackaday.IO page explains that the idea is based on the work of [stevenart], with code adapted for the SSD1306 display and some tweaks made to the circuit. While [mircemk] says the code could be modified for stereo as long as the two displays don’t have conflicting I2C addresses, he decided to simply duplicate the whole setup for each channel to keep things simple. With as cheap as some of these parts are nowadays, it’s hard to blame him.

[mircemk] has provided source code for a couple different styles of VU indicators, the colors of which can easily be inverted depending on your tastes. He also clarifies that the jerky motion of the virtual “needle” seen in the video is due to the camera; in real-life it sweeps smoothly like the genuine article.

Much like the project that aimed to recreate authentic “steam gauges” with e-paper displays, this as an excellent technique to file away for use in the future. Compared to authentic analog gauges, these digital recreations are quicker and faster to implement, plus going this route prevents any antique hardware from going on the chopping block.

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Don’t Guess, Listen To Your Plants’ Pleas For Water

October 23, 2020 by 5 Comments

Plants are great to have around, but they all have different watering needs. If only they could cry out when they’re thirsty, right? Well, now they can. All you need to hear them suffer is your very own Klausner Machine. [RoniBandini] based the Klausner machine on one of Roald Dahl’s short stories, which features an inventor who builds a machine that can make audible the sound of plants shrieking whenever they’re cut.

In [RoniBandini]’s version of the Klausner Machine, the point is to judge the plant’s feelings based on its soil moisture content. An Arduino Nano reads in from the soil moisture sensor, and if the soil is dry, the plant screams. If the soil is moist, the plant emits happy sounds from DF Player Mini and SD card.  We think the analog meters are a great touch, and the jumping needles really anthropomorphize the plant.

Go forth and gain a better appreciation for your plants’ feelings, because this project is wide open. Maybe it will help you water them more often. Some plants need to be cut back, so we think it would be cool if you could make it scream when you take a cutting. Check out the demo after the break.

This is isn’t the first time we’ve seen an analog meter used in conjunction with soil moisture. What is a VU meter, anyway? Our own [Dan Maloney] really moved the needle on the subject a while back.

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The VU Meter And How It Got That Way

August 9, 2018 by 44 Comments

Given its appearance in one form or another in all but the cheapest audio gear produced in the last 70 years or so, you’d be forgiven for thinking that the ubiquitous VU meter is just one of those electronic add-ons that’s more a result of marketing than engineering. After all, the seemingly arbitrary scale and the vague “volume units” label makes it seem like something a manufacturer would slap on a device just to make it look good. And while that no doubt happens, it turns out that the concept of a VU meter and its execution has some serious engineering behind that belies the really simple question it seeks to answer: How loud is this audio signal?

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