Our favorite raft of otters is back at it again with another display of open source audio prowess as they bring us the OtterCastAmp, the newest member of the OtterCast family of open source audio multitools. If you looked at the previous entry in the series – the OtterCastAudio – and thought it was nice but lacking in the pixel count or output power departments then this is the device for you.
The Amp is fundamentally a very similar device to the OtterCastAudio. It shares the same Allwinner S3 Cortex-A application processor and runs the same embedded Linux build assembled with Buildroot. In turn it offers the same substantial set of features and audio protocol support. It can be targeted by Snapcast, Spotify Connect or AirPlay if those are your tools of choice, or act as a generic PulseAudio sink for your Linux audio needs. And there’s still a separate line in so it source audio as well.
One look at the chassis and it’s clear that unlike the OtterCastAudio this is not a simple Chromecast Audio replacement. The face of the OtterCastAmp is graced by a luscious 340×800 LCD for all the cover art your listening ear can enjoy. And the raft of connectors in the back (and mountain of inductors on the PCBA) make it clear that this is a fully fledged class D amplifier, driving up to 120W of power across four channels. Though it may drive a theoretical 30W or 60W peak across its various outputs, with a maximum supply power of 100W (via USB-C power delivery, naturally) the true maximum output will be a little lower. Rounding out the feature set is an Ethernet jack and some wonderfully designed copper PCB otters to enjoy inside and out.
As before, it looks like this design is very close to ready for prime time but not quite there yet, so order at your own risk. Full fab files and some hints are linked in the repo mentioned above. If home fabrication is a little much it looks like there might be a small manufacturing run of these devices coming soon.
When Google halted production of the Chromecast Audio at the start of 2019, there was a (now silent) outcry. Fans of the device loved the single purpose audio streaming dongle that delivered wide compatibility and drop-dead simplicity at a rock bottom $35 price. For evidence of this, look no further than your favorite auction site where they now sell for significantly more than they did new, if you can even find an active listing. What’s a prolific hacker to do about this clear case of corporate malice? Why, reinvent it of course! And thus the Otter Cast Audio V2 was born, another high quality otter themed hack from one of our favorite teams of hardware magicians [Niklas Fauth, Jan Henrik, Toble Miner, and Manawyrm].
The Otter Cast Audio is a disc about the shape and size of standard Chromecast (about 50mm in diameter) and delivers a nearly complete superset of the original Chromecast Audio’s features plus the addition of a line in port to redirect audio from existing devices. Protocol support is more flexible than the original, with AirPlay, a web interface, Spotify Connect, Snapcast, and even a PulseAudio sink to get your Linux flavored audio bits flowing. Ironically the one thing the Otter Cast Audio doesn’t do is act as a target to Cast to. [Jan] notes that out of all the protocols supported here, actual Cast support was locked down enough that it was difficult to provide support for. We’re keeping our fingers crossed a solution can be found there to bring the Otter Cast Audio to complete feature parity with the original Chromecast Audio.
But this is Hackaday, so just as important as what the Otter Cast Audio does is how it does it. The OtterCast team have skipped right over shoehorning all this magic into a microcontroller and stepped right up to an Allwinner S3 SOC, a capable little Cortex A7 based machine with 128 MB of onboard DDR3 RAM. Pint sized by the bloated standards of a fully interactive desktop, but an absolutely perfect match to juggling WiFi, Bluetooth, Ethernet, and convenient support for all the protocols above. If you’re familiar with these hackers’ other work it won’t surprise you that what they produced here lives up to the typical extremely high quality bar set by such wonders as this USB-C adapter for JBC soldering iron handles and this TS-100 mainboard replacement.
Digital electronics are all well and good, but it’s hard to ignore the organic, living qualities of the analog realm. It’s these circuits that Kelly Heaton spends her time with, building artistic creations that meld the fine arts with classic analog hardware to speak to the relationship between electronics and nature. During her talk at the 2019 Hackaday Superconference, Kelly shared the story of her journey toward what she calls Electronic Naturalism, and what the future might bring.
Kelly got her start like many in the maker scene. Hers was a journey that began by taking things apart, with the original Furby being a particular inspiration. After understanding the makeup of the device, she began to experiment, leading to the creation of the Reflection Loop sculpture in 2001, with the engineering assistance of Steven Grey. Featuring 400 reprogrammed Furbys, the device was just the beginning of Kelly’s artistic experimentation. With an interest in electronics that mimicked life, Kelly then moved on to the Tickle Me Elmo. Live Pelt (2003) put 64 of the shaking Muppets into a wearable coat, that no doubt became unnerving to wear for extended periods.
Analog electronics parallel living organisms while programmable logic merely simulates life.
Wanting to create art with a strong relationship to organic processes, Kelly focused on working with discrete components and analog circuitry. Basic building blocks such as the astable multivibrator became key tools that were used in different combinations to produce the desired effects. Through chaining several oscillators together, along with analog sequencers, circuits could be created that mimicked the sound of crickets in a backyard, or a Carolina wren singing in a tree.
Some of us are guilty of picking up questionable hardware from garage sales, fleamarkets, and well-meaning relatives. There is a balance between turning down a good investment and hoarding, and if we figure out how to tell the difference you will be the first to know. [Clem Mayer] may start on the side of unwise acquisition, but he pushes a broken fetal detector into the realm of awesome by converting it to an analog synthesizer, born to headline at an Eastern European dance party.
He starts with a basic teardown, and we get to see how old hardware was serviceable with only two standard screws. It is a good thing too, because the nickel-cadmium batteries are older than some of you and they are in need of replacement. New nickel-metal hydride batteries got it up and running but [Clem] does not have a baby bump so its functionality turned to Pink Floyd era synthesizer circuit bending. Circuit bending involves modifying a circuit for sound it was not intended to make.
Have you ever wanted to build a high quality audio crossover and amplifier? [Rouslan] has put a lot of thought into making his dual amplifier studio monitor both high quality and simple to build.
With a concise schematic, a meaningful block diagram, and simulation results to boot, his well-written post has everything you need to build self-powered bi-amped speakers based on the LM4766 from Texas Instruments. It is great to see simulations which verify the functionality of the circuit, this can go a long way when working with complicated analog filters and audio circuitry. For those of you who do not have access to PSPICE (an expensive professional simulation tool), [Rouslan] uses LTspice from Linear Technology. TINA-TI from Texas Instruments is another great free alternative.
Additionally, [Rouslan] goes over the typical issues one has with a bi-amplifier studio monitor, such as phase misalignment and turn-on pop, and then provides a solution. Note that his project is powered by 20VAC, which requires an external transformer to convert the 120VAC in the wall to 20VAC. Be careful with high voltages! In the future, adding a high quality voltage regulator will most likely increase the performance.
His post finishes up with a very clean circuit board, which he ordered from OSH Park. With such a complete design, there is nothing keeping you from building your own. Go out and put that old speaker sitting in your basement to good use!
If you don’t have an old speaker sitting around, check out these very cool DIY speakers.
Here’s the scenario: You’ve got the rage to play som CoD (we’re more GTA fans but whatever) but the monitor you’re going to play on has no speakers. You can get a crystal clear image using HDMI, but getting sound is a different matter. What’s the fix? Crack open your PS3 and solder on some audio connectors.
[Paul] knew there is a special cable that breaks out analog audio. Like original Xbox hacking of ages past, there is now plenty of information online about the internals of these machines. He grabbed a copy of the A/V pinout and found the analog audio pins. After soldering on this pair of RCA cables he cut savaged a hole in the case and put the console back together. The machine he’s working with is a salvaged unit with no Blu-ray drive — he links to his past posts on the repair process. You may be thinking what good is it without an optical drive? Remember, this is the beginning of the Internet age… everything is downloadable.