pro audio

4 Articles

Salvaged Meter Movements Really Pop In This DIY VU Meter Bridge

February 17, 2024 by 3 Comments

If you’re going to build a nice VU meter bridge for the recording studio, the first thing you need is a nice pair of VU meters. But lest you think it’s as easy as putting some meters into a nice box and calling it a day, think again.

This project comes to us from [Frank Olson], whose projects usually incorporate wood as part of the mechanism, as with his famous wooden ribbon microphone. This build does indeed use wood, and to excellent effect, but only in the project’s final enclosure. Before that, [Frank] had salvaged a pair of good-looking moving coil meters from an old tape recorder. He muddled through some ideas before settling on a design. A NE5532 dual-channel audio buffer module is used as a preamp, with each channel feeding into a bridge rectifier before heading to the meter. Wisely, [Frank] chose to illuminate the meters with their existing incandescent bulbs, so a small DC-DC supply was added to provide the necessary 8 volts.

As for the enclosure, that’s where [Frank]’s experience working with veneers paid off. He chose mahogany, carefully cut all the pieces to shape with a knife, and glued it all up with CA glue — at least we assume it was CA; based on previous efforts, he uses a lot of the stuff. The tung oil finish looks fantastic, and the completed build aesthetic looks great! The video below shows it all.

If you need some backstory on the VU meter, we can help with that.

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PipeWire, The Newest Audio Kid On The Linux Block

June 23, 2021 by 65 Comments

Raise your hand if you remember when PulseAudio was famous for breaking audio on Linux for everyone. For quite a few years, the standard answer for any audio problem on Linux was to uninstall PulseAudio, and just use ALSA. It’s probably the case that a number of distros switched to Pulse before it was quite ready. My experience was that after a couple years of fixing bugs, the experience got to be quite stable and useful. PulseAudio brought some really nice features to Linux, like moving sound streams between devices and dynamically resampling streams as needed.

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Homebrew Binaural Microphone Lets You Listen Like A Human

May 31, 2020 by 22 Comments

We humans may not have superpowers, but the sensor suite we have is still pretty impressive. We have binocular vision that autofocuses and can detect a single photon, skin studded with sensors for touch, heat, and pain, and a sense of smell that can detect chemicals down to the parts per trillion range. Our sense of hearing is pretty powerful, too, allowing us to not only hear sounds over a 140 dB range, but also to locate its source with a fair degree of precision, thanks to the pair of ears on our heads.

Recreating that binaural audio capture ability is the idea behind this homebrew 3D microphone. Commercially available dummy head microphones are firmly out of the price range of [LeoMakes] and most mortals, so his was built on a budget from a foam mannequin head and precast silicone rubber ears, which you can buy off the shelf, because of course you can.

Attached to the sides of the foam head once it got the [Van Gogh] treatment, the ears funnel sound to tiny electret cartridge microphones. [Leo] learned the hard way that these little capsule mics can’t use the 48-volt phantom power that’s traditionally pumped up the cable to studio microphones; he fixed that problem with a resistor in parallel with the mic leads. A filtering capacitor, an RC network between the cold line and ground on the balanced audio line, and a shield cleverly fashioned from desoldering braid took care of the RF noise problem.

The video after the break shows the build and test results, which are pretty convincing with headphones on. If you want to build your own but need to learn more about balanced audio and phantom power, we’ve got a short primer on the topic that might help.

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The Hot And Cold Of Balanced Audio

July 27, 2018 by 45 Comments

A few summers of my misspent youth found me working at an outdoor concert venue on the local crew. The local crew helps the show’s technicians — don’t call them roadies; they hate that — put up the show. You unpack the trucks, put up the lights, fly the sound system, help run the show, and put it all back in the trucks at the end. It was grueling work, but a lot of fun, and I got to meet people with names like “Mister Dog Vomit.”

One of the things I most remember about the load-in process was running the snakes. The snakes are fat bundles of cables, one for audio and one for lighting, that run from the stage to the consoles out in the house. The bigger the snakes, the bigger the show. It always impressed me that the audio snake, something like 50 yards long, was able to carry all those low-level signals without picking up interference from the AC thrumming through the lighting snake running right alongside it, while my stereo at home would pick up hum from the three-foot long RCA cable between the turntable and the preamp.

I asked one of the audio techs about that during one show, and he held up the end of the snake where all the cables break out into separate connectors. The chunky silver plugs clinked together as he gave his two-word answer before going back to patching in the console: “Balanced audio.”

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