The difference between bitcrushers and sample rate reducers

bit

If you look around a few electronic music forums, you’ll see a lot of confusion over the difference between a bitcrusher – a filter that reduces the bit depth of an audio signal – and a sample rate reducer – a filter that does exactly what its name implies. With the popularization of 8-bit and retro synth music, this difference is obviously of grave import of concern to saints and kings alike. [Michael] is more than happy to walk us through the difference with real-time sample and bit rate adjustment with his audio hacker board.

The audio hacker board is an Arduino shield with a 12-bit DAC and a 12-bit ADC. With two 1/8″ jacks and a pair of pots, [Michael] was easily able to whip up a sketch that is able to adjust the sample rate and bit depth of an audio signal in real-time.

Contrary to nearly everyone’s opinion of what ‘8-bit’ music is, it’s actually the sample rate that makes music sound like a cassette deck jury rigged into a Nintendo Entertainment System. Reducing the bitrate just makes any audio source sound louder and worse.

Check out the excellent demo video of the effect of bitcrushers and sample rate reducers below.

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Boominator solar stereo keeps the music pumping even in cloudy weather

boominator

Despite 40-some years of product improvements, boomboxes today still require a half dozen D-cell batteries and measure their life in single digit hours.  After this, the batteries get chucked in the trash. Tired of the absurd cost and quantity of batteries required in a typical boombox, reddit user [anders202] has whipped up a solution that will keep the party going and the landfills empty. Using some off-the-shelf components and some impressive woodworking skills, he created the “Boominator”.

Despite its environmentally-conscious design, this green machine packs a whallop. Using its dual 10W solar panels, it can drive four woofers and tweeters to produce an estimated 102dB of sound with power to spare.  This extra juice can be used to charge its two internal 7.2Ah batteries or a cellphone using the integrated USB charging ports.  Better still, Anders chose amorphous solar panels (as opposed to crystalline) which produce power even in cloudy weather as demonstrated during a cloudy day at the Roskilde festival in Denmark.  For more information, check out the reddit comment thread.

Video demo after the jump

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I keep my tunes in an ammo can

ammo-can-boombox

Calling this a boom box is at least slightly ironic. Instead of high explosives it now carries high decibels in its new life as a self-contained sound system.

Despite the conspicuous power cord a peek inside reveals a big enough battery to keep the tunes playing for hours on end. [King Rootintootin] kept the cost on the build down since he was given the used speakers and amp by his girlfriend’s dad. The amp kicks out about 25 Watts with the battery rated at 7.2 Ah. He added a charger and routed the controls to the side of the ammo box so that it can be charged without removal. The only external component is the audio jack which connects it to the music source.

One of the suggested improvements from the Reddit thread is to add baffles inside of the enclosure so that sound from the two stereo channels doesn’t interfere with each other.

Simple looking Antique Internet Radio has a lot under the hood

rpi-internet-radioAt first glance you might not even notice that this 1934 radio has been altered. But close study of the tuning dial will tip you off that changes have been made. It still scrolls through stations just like the original. But it’s not a wheel with some numbers on it. The rotary motion is an effect produced by an LCD screen.

This is the second time we’ve seen one of [Florian Amrhein's] Internet radio projects. The first used guts from a Laptop paired with an Arduino to pull everything together. This time he’s chosen to wield a Raspberry Pi board. It feeds a USB sound card for a bit better quality. A small amplifier board us used to power one large speaker behind the original grill of the radio.

Check out the demo video to see that radio dial in action. It’s delightful that he went to the trouble to emulate a rotating disc to keep with the theme of the project.

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Car stereo AUX input taps into CD ribbon cable

RadioAuxInput-banner

[Gezepi] wanted to add an auxiliary input to the stereo in his 1994 Camry. At first look there wasn’t an easy way to patch into the system. But a bit of probing with an oscilloscope and figured out that he could inject audio through the CD ribbon cable shown above. The CD reader is a self-contained unit that receives commands through the cable, and passes analog stereo audio back to the receiver portion of the head unit. We’re not sure how he figured out which pins to tap into, but it may have been as easy as probing with some headphones while a CD is playing.

The extent of his hack is documented in the image below. He cut the two audio leads on the CD side of the ribbon cable, then soldered his auxiliary jack on the receiver side of the cable connector. This ensures that two audio signals aren’t being piped into the receiver at the same time. Unfortunately it also means that he won’t be able to use the CD player. We have seen other methods that use a special audio jack as a pass-through which cuts the connection when a jack is inserted. That’s the method used in this Subaru hack.

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Letting Bluetooth take the wires out of your headphones

bt-wireless-headphones

This picture shows the gist of [Alan's] hack to transition his wired headphone to internalize a Bluetooth audio receiver (translated).

He starts with a pair of wired “ear muff” style headphones and an aftermarket Bluetooth audio adapter that he’s been using with them. But if you’re not going to plug them into the audio source why have six feet of extra wire hanging about? [Alan] ditched the plastic case surrounding the Bluetooth hardware and cracked open the earpieces to find room for it. It’s a tight fit but there was just enough room.

It is unfortunate that the headphone design doesn’t already have a wired crossover hidden in the arc connecting the earpieces. Alan strung some of that red wire himself to connect the two speakers. The board is mounted so that the USB port is located where the wires used to enter the plastic body. This makes it a snap to plug them in when they need a recharge.

You can play a little “Where’s Waldo” with this one by trying to spot the Raspberry Pi in his build log.

 

Beck’s beer bottle sound recording

becks-beer-edison-cylinder

This beer bottle includes recorded audio etched into the glass. But you certainly won’t find half an album included with your next sixer. This is a one of a kind item that took a team of engineers to craft.

The idea comes from Phonographic Cylinders invented by [Thomas Edison]. Analog audio was etched into cylinders made of wax which could then be played by a needle and amplifying horn. The beer bottle is a similar size of cylinder, but etching the audio signal into glass is a horse of a different color. The video below includes a recounting of the development process from the guys who pulled it off. It includes using hard drive parts and special processing filters that remove harmonics introduced by the milling rig.

We’re sure you’ve figured it out by now; this is an advertisement. We say good! This is the kind of advertising we want. It’s topical, well targeted, and worth paying attention to. We felt the same way about the recent Oreo campaign and that Skittles hack. We hope that ad execs will take note of this.

By the way, it is possible to do this stuff at home. Check out the guy who made an Edison Cylinder wedding ring.

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