A Very Large VU Meter Indeed

May 16, 2017 by Jenny List 18 Comments

It used to be a must-have on any hi-fi, a pair of moving coil meters or LED bar graphs, the VU meter. Your 1980s boombox would have had them, for example. VU, for “Volume Units”, is a measure of audio level, and the fashion for its visual measure in consumer audio equipment seems now to have largely passed.

The LED bar graph VU meters were invariably driven by the LM3915, a chip that contains a resistor ladder and a stack of comparators which can drive LEDs directly. [Juvar] has taken an LM3915, and used it to drive a set of opto-isolated triacs which in turn drive a stack of appropriately coloured mains LED bulbs concealed within an Ikea Vidja lamp. The result is a huge and very bright VU meter that is as much a lighting effect as it is a measure of sound level.

He’s posted a video of the lights in action, and we’ve placed it below the break. There is a cameo appearance from his cat, and one can’t escape the feeling that it is wasted on a small room and would be at its best before a dance floor. Still, it’s a neat lighting effect and a new use for a classic integrated circuit.

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Adding Stereo VU Meters To A Turntable

January 28, 2017 by Jenny List 8 Comments

A pleasing development for those with an interest in audio equipment from decades past has been the recent resurgence in popularity of vinyl records. Whether you cleave to the view that they possess better sound quality or you simply like the experience of a 12″ disk with full-size cover art and sleeve notes, you can now indulge yourself with good old-fashioned LPs being back on the shelves.

[Michael Duerinckx] is a fan of older trance records, and has an Ion Pure LP turntable which is fortunately for him not such an exclusive piece of audio equipment that it can’t be readily hacked. The hack he’s applied to it is a relatively simple one but nonetheless rather attractive, he’s added a set of LED VU meters in a ring round the edge of the platter.

Behind the LEDs is the trusty LM3915, an integrated circuit which will no doubt be familiar to any reader whose earlier life was spent among 1970s and 1980s audio gear. Internally it’s a stack of comparators and a resistor ladder, and it simply turns on the required number of outputs to match the level on its input. He’s put a pair of them on a little PCB with an associated PSU regulator, and mounted the LEDs in a row of holes drilled in the MDF base board of the turntable following the edge of the platter. Power and audio come from the turntable’s circuit board, which contains a preamplifier and the USB audio circuitry. A traditional turntable with a low-level output would not be able to drive an LM3915 directly.

This is a relatively straightforward project and the turntable itself isn’t necessarily the most accomplished on the market, but it’s very neatly executed and looks rather pretty.

Turntable projects are not as common as you’d expect here at Hackaday, but we’ve had a few. There was this concrete example for instance, and a very pretty one using layered plywood.

Courtesy of SoMakeIt, Southampton Makerspace.

“What Is My Purpose?” You Amplify And Display Signals.

December 19, 2016 by Kristina Panos 8 Comments

[Andy_Fuentes22] likes to stream music, but is (understandably) underwhelmed by the sound that comes out of his phone. He wanted to build something that not only looks good, but sounds good. Something that could stream music through a Chromecast or a Raspi, but also take auxiliary input. Something awesome, like the Junkbots Sound System.

The ‘bots, named LR-E (Larry) and R8-CHL (Rachel), aren’t just cool pieces of art. They’re both dead-bug-walking bots with an LM386-based amplifier circuit and an AN6884-based VU meter in their transparent, industrial relay bodies. LR-E is the left channel, and his lovely wife is the right channel. The best part is that they are wired into the circuit through their 3.5mm plug legs and the corresponding jacks mounted in the Altoids tin base.

[Andy] built this labor of love from the ground up. He started with some very nice design sketches and took a bazillion pictures along the way. We think it sounds pretty good, but you can judge for yourself after the break. If VU meters are your jam, here’s another that’s built into the speaker.

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This VU Meter Is Built Into The Speaker

November 29, 2015 by James Hobson 20 Comments

Depending on the music you’re listening to, watching a VU meter bounce to the music is always a good time. So why not integrate the VU meter right into the audio source? That’s what [Matikas] did, and it’s pretty fantastic.

He started with a pair of speakers he had and picked up some NeoPixel LED strips. Carefully wrapping the LED strips around the inside circumference of each speaker, the LEDs fit behind the speaker grills, giving it a cool effect when they’re on.

To control the LEDs, he’s using an Arduino Uno (Atmega328p) which measures the audio level in order to modulate the LED output. A bit of software later (shared on GitHub if you’re interested!) and the VU meters were ready for action — check it out!

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A VU-meter Indicator For A Commodore 1530 Datasette

April 11, 2015 by Anool Mahidharia 9 Comments

For present-day owners of vintage Commodore computers, keeping data and programs safe and backed up is top priority. Disk drive storage was more common in the US, whereas in Europe, the audio cassette was the preferred medium of storage.

The Datasette device was what allowed interfacing the cassettes to the computer. Tape head alignment was critical to successfully writing and reading data to the cassette. Some models of the Datasette came with a small hole above the keys, to allow access to the adjustment screw of the tape head azimuth position. Tweaking this while looking at a signal meter could help you improve the signal from a bad cassette and prevent load errors. [Jani] tried a commercial solution called “Load-IT” which had a LED bargraph, but it couldn’t help much dealing with tapes with very bad signals. So he built a signal strength meter for his Datasette. He calls it the VU-sette since it uses an analog style meter quite similar to the VU-meters found in many audio equipment.

The hardware is simple and uses commonly available parts. The analog meter is extracted from a Battery Checker sourced from eBay. An op-amp drives the analog meter, and another transistor drives a separate speaker. This can be used to listen in on the cassette, if the speaker is enabled via a push button. [Jani] first breadboarded and tested the circuit before ordering out prototype boards.

To test performance, [Jani] used FinalTAP, a tool for examining, cleaning and restoring digitized data cassette tapes (TAP files) for the Commodore 64 computer. The “LOAD-IT” version worked well with tapes that were in fairly good condition. But his VU-sette version allowed him to adjust the head more precisely and get out a much better read from bad tapes. While on the subject, check out this nice 7-segment bubble LED digital counter for the 1530.

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3D Spectrum Analyzer Uses 1280 LEDs

March 23, 2015 by Ethan Zonca 47 Comments

One of [Dooievriend]’s friends recently pressed him into service to write software for a 3d spectrum analyzer/VU that he made. The VU is a fairly complex build: it’s made up of 1280 LEDs in a 16x16x5 matrix controlled by a PIC32 clocked at 80MHz. [Dooievriend] wrote some firmware for the PIC that uses a variation on a discrete Fourier transform to create a 3D VU effect.

When [Dooievriend] set out to design the audio analyzing portion of the firmware, his mind jumped to the discrete Fourier transform. This transform calculates the amplitude in a series of frequency bins in the audio—seemingly perfect for a VU. However, after some more research, [Dooievriend] decided to implement a constant Q transform. This transform is very similar to a Fourier transform, but it takes into account the logarithmic way that the human ear interprets sound.

[Dooievriend] started implementing the constant Q transform using an interrupt-based sampler, but he quickly ran into issues with slow floating-point math on his PIC32 (which doesn’t have a hardware floating-point unit). Thankfully he rewrote his code using fixed-point math, and the transform runs nearly real-time. Check out the video after the break to see the VU in action, and a second video that gives some details on the hardware build.

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A Real-Time Networked VU Running On The ESP8266

February 17, 2015 by Ethan Zonca 21 Comments

Even though the ESP8266 WiFi chipsets are really cheap (and can be somewhat challenging to work with), they still pack a lot of processing power. For instance, [Mr.jb.swe] took one of these modules and made a stand-alone live VU meter with WS2812B LED strip. The VU runs entirely on the ESP chip, without any additional microcontroller. It’s an example we think a lot of projects could follow to do away with unused horsepower (extra microcontrollers) sometimes used to avoid programming directly on the ESP. The stuff you can do with these modules is wild… did you see this WiFi signal strength mapping project?

The ESP chipset acts as a UDP client which receives packets from a WinAmp plugin that [Mr.jb.swe] wrote. The plugin continuously calculates the dB of whatever track is playing and streams it over WiFi to his ESP8266. He also mentions that the ADC of the ESP chipset could be used to sample audio as well, although that pretty much eliminates the need for WiFi.

The whole setup is very responsive even though the processor is parsing UDP messages, driving the WS2812 strip, and driving a small OLED display for debug—and it doesn’t even use a separate microcontroller. [Mr.jb.swe] also posted snippets of his code to get you started on your own project. Check out the videos after the break to see it in action.

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