As consumer electronics companies chase profits on tighter and tighter margins, it seems like quality is continually harder to find for most average consumer-grade products. Luckily, we don’t have to hunt through product reviews to find well-built merchandise since we have the benefit of survivorship bias to help us identify quality products from the past that have already withstood the test of time. [Tom] has forever been fond of this particular Sony TV/radio combo from the ’70s so he finally found one and set about modernizing it in a few key ways.
Among the modifications to this 1978 Sony FX-300 include the addition of a modern color display, Bluetooth, an upgraded FM radio, and a microphone. At the center of all of this new hardware is a Teensy 4 which [Tom] has found to be quite powerful and has enough capabilities to process the audio that’s being played in order to make visual representations of the sound on the screen. He also implemented a bitcrusher filter and integrated it into the controls on the original hardware. He’s using an optimized version of this library to cram all of that processing ability into such a small chip, and the integration of all this new hardware is so polished that it looks like it could be an original Sony stereo from the modern era.
While some may complain about restomod-type builds like this, we don’t really see any need to be arbitrarily or absolutely faithful to bygone eras even if the original hardware was working properly in the first place. What works is taking the proven technology of the past and augmenting it with modern features to enjoy the best of both worlds. Much like this hi-fi stereo which blends the styles and technology of the 90s with that of the 60s in an equally impressive way.
When it comes to audio effects, you have your delay, reverb, chorus, phasing, and the rest that were derived from strictly analog processes. Compared to the traditional way of doing things, digital audio is relatively new, and there is still untapped potential for new processes and effects. One of those is the bit crusher, an effect that turns 8- or 16-bit audio into mush. [Electronoob] wanted to experiment with bitcrushing, and couldn’t find what he wanted. Undeterred, he built his own.
There are two major effects that are purely in the digital domain. The first is the sample rate reducer. This has a few interesting applications. Because [Shannon] and [Nyquist] say we can only reproduce audio signals less than half of the sample rate; if you run some audio through a sample rate reducer set to 1kHz, it’ll sound like crap, but you’ll also only get bass.
The bitcrusher is a little different. Instead of recording samples of 256 values for 8-bit audio or ~65000 values for 16-bit audio, a one-bit bitcrusher only records one value – on or off. Play it through a speaker at a decent sample rate, and you can still hear it. It sounds like a robotic nightmare, but it’s still there.
[Electronoob] created his bitcrusher purely in software, sending the resulting bitcrushed and much smaller file to an Arduino for playback. Interestingly, he’s also included the ability to downsample audio, giving is project both pure digital effects for the price of one. 1-bit audio is a bit rough on the ears, but 2, 3, and 4-bit audio starts to sound pretty cool, and something that would feel at home in some genres of music.
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.