Hackaday Podcast 028: Brain Skepticism Turned Up To 11, Web Browsing In ’69, Verilog For 7400 Logic, 3D Printing In Particle Board

Hackaday Editors Mike Szczys and Elliot Williams cover the most interesting hacks over the past week. So much talk of putting computers in touch with our brains has us skeptical on both tech and timeline. We celebrated the 40th Anniversary of the Walkman, but the headphones are the real star. Plus, Verilog isn’t just for FPGAs, you can synthesize 7400 circuits too! Elliot is enamored of an additive/subtractive printing process that uses particle board, and we discuss a couple of takes on hybrid-powered drones.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

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Forget The Walkman: It’s The Headphones

Forty years ago this month, a product was launched  in Japan that would have such a huge impact on the consumer electronics market that we are still using its descendants today. The story goes that one of the Sony founders would listen to music while traveling for the business, and found the company’s existing products cumbersome and awkward so asked his engineers to design something more convenient.

The resulting prototype became the Sony MDL-3L2, a set of miniaturised hi-fi headphones with distinctive foam earpads and a sliding metal headband that in total weighed an astoundingly svelte 45 g. It was paired with a cassette player called a “Walkman” derived from the company’s existing recorder that had been intended for journalists, and went on to sell in the millions. The market for headphones would never be the same again, and if you have a set of lightweight cans in your possession then this was their revolutionary progenitor.

But Hang On, What’s So Special About Headphones?

You probably won’t have heard the Walkman’s 40th anniversary described in those terms in the various reports covering the event, because of course the social impact of the portable music player rather than its headphones is what people remember. The joy of making a mix tape, of listening to The Human League on the bus, and of the adult disapproval of anything involving Kids Having Fun. Previously, music had been a static affair involving bulky record players, but now it could be taken anywhere. The other youth audio icon of that era, the boombox, simply couldn’t match the Walkman, and everybody wanted one.
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High-End Headphones Get Flexible Boom Upgrade

It seems a reasonable assumption that anyone who’d be willing to spend a few hundred dollars on a pair of headphones is probably the type of person who has a passion for high quality audio. That, or they work for the government. We’re fairly sure [Daniel Harari] falls into that former category though, given how much thought he gave to adding a decent microphone to his Sennheiser HD650 headphones.

Not happy with the results he got from microphones clipped to his shirt or mounted on a stand, [Daniel] realized what he really wanted was a sensitive boom microphone. This would be close enough to his mouth that it wouldn’t pick up stray noises, but at the same time not obstruct his field of view or otherwise get in the way.

He found a few options on the market which would allow him to mount a boom microphone to his HD650’s, but he didn’t want to stick anything to them and risk scratching the finish so those weren’t really an option. [Daniel] decided to go the DIY route, and eventually settled on a microphone that would mount to the headphone’s existing connector which plugs in at the bottom of the cup.

To make his mount, he 3D printed a two piece clamp that could be screwed together and securely attach to the connector without making any permanent changes. Once he had that base component printed, he salvaged the flexible metallic neck from a cheap USB light and used that to hold the female 3.5mm connector. Into that he’s plugged in a small commercially available microphone that is usually used on voice recorders, which [Daniel] said sounds much better than even the larger mics he had tested.

Finally, he used Sugru to encapsulate the wires and create a flexible strain relief. The whole assembly is very light, easily movable, and perhaps most importantly, didn’t require any modifications or damage to a pair of headphones which have a retail price that could double as a car payment.

It’s been a few years since we’ve seen anyone brave enough to hack their pricey Sennheiser headphones. But in the past we covered a modification which gave them an infusion of Bluetooth and even one that reversed a sneaky manufacturer hardware limitation.

A Bluetooth Upgrade For An Unusual Set Of Headphones

We will have all picked up something from a junk pile or swap meet in our time that caught our eye not because we needed it but because it looked cool. [Quinn Dunki] did just that with an irresistible set of 1980s air traffic control headphones. What did she do with them? Turn them into a set of Bluetooth headphones of course!

The ‘phones in question are particularly interesting, as they turned out upon inspection to be a two-way radio in disguise. Cracking them open revealed a radio board and a logic board, and what makes them particularly interesting to this Hackaday scribe’s eye is their choice of frequency. She finds a crystal with a VHF airband frequency multiplier and concludes that they must operate there, but a look at the photos reveals all the ingredients of a classic AM or low HF receiver. There is a ferrite rod antenna and a variable capacitor, if we didn’t know that these were very high-end professional ‘phones we’d almost suspect they were a novelty AM radio from Radio Shack. If any readers can shed any light on the frequency and purpose of this device, we’re all ears.

The conversion involved a Sparkfun Bluetooth module breakout board paired with a little audio power amplifier. The original drivers were high-impedance and one of them had died, so she replaced them with a modern pair of identical size. The control buttons were mounted in the headphone’s external housing, after a wrong turn into attempting to create a custom enclosure. The result is a rather novel but high-quality set of ‘phones, and one we rather wish we’d found ourselves.

Vintage Headphones Bluetooth Conversion Goes The Extra Mile

[KaZjjW] wanted to retrofit a pair of nicely styled vintage headphones to be able to play wirelessly over Bluetooth. In principle this is an easy task: simply stick a Bluetooth audio receiver on the line-in, add a battery, and you’re all set. However, [KaZjjW] wanted to keep the aesthetic changes to the headphones at an absolute minimum, retaining the existing casing and volume control, whilst cramming the electronics entirely inside and out of sight.

With the inherent space constraints inside the cups of the headphones, this proved to be quite a challenge. The existing volume potentiometer which hung half outside the case was remounted on an ingenious hinge made of two PCBs, with the pot floating next to a surface mounted switch. This allowed it to not only control the volume, but also act as an on/off switch for the Bluetooth. The only other existing cuts in the casing were a circular hole for the audio cable, and a slit for the cable strain relief. These worked perfectly for an LED status indicator and micro-USB battery charging.

The main chip used for receiving audio over Bluetooth was the BM62 by Microchip. It’s a great all-in-one solution for this kind of project as it has built-in battery charging, an on-board DAC and audio amp, as well as a serial control interface. In part 2 of the project log, the process of programming the BM62 was documented, and it was painful – it’s a shame that the software support lets it down. But a hacker will always find a way, and we’ve seen some pretty neat hacks for reprogramming existing chips in off-the-shelf Bluetooth headphones.

Two PCBs for the pot button hinge, one for the LED and micro-USB connector, as well as one for the Bluetooth receiver and a PIC. That’s four PCBs in a pretty small space, enabled by some commendable design effort both electronically and mechanically. It certainly paid off, as the finished product looks very slick.

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Wireless Headphone Hack Dangles Batteries Like Earrings

Koss Porta Pro headphones are something of a rarity in the world of audio gear: they’re widely regarded as sounding great, but don’t cost an exorbitant amount of money. Since the line was introduced in 1984, they’ve been the go-to headphones for those who don’t subscribe to the idea that you should have to take out a loan from the bank just to enjoy your music.

[Jake Bickhard] is a confirmed Porta Pro disciple, owning enough pairs of them that he’s cagey about confirming how many are actually kicking around his home. The only thing he doesn’t like about them is the fact that they’re wired. As it happens, Koss just recently came out with a Bluetooth version of the venerable headphones. But he thought he could do just as well combining a pair of his with a water damaged pair of Bluetooth earbuds he had lying around.

The Porta Pros are easy to take apart, and removing the old wire was no problem. He then cut the “buds” on the Bluetooth earbuds he had, with the intention of just striping the wires and soldering it up to the pads on the Porta speakers. But things didn’t quite go as expected.

What [Jake] hadn’t realized was that the battery for the Bluetooth earbuds wasn’t in the main housing, the power comes from a tiny battery inside each bud. That meant he needed to keep the batteries connected even though the Porta Pro obviously doesn’t have a spot to mount them. In the future he says he’ll address the issue properly, but for now the two batteries hang from the headphones: making it look like he’s wearing the world’s ugliest earrings. But at least he’s happy with the performance of the finished modification, saying they’re even louder now than when they were when wired.

This is a perfect project if you’re cursed with a mobile device that had enough “courage” to take the headphone jack away from you. Though you might first want to study the fine art of soldering headphone wires.

Turning 8-Track Player Into A Walkman

Following time backward, for portable music we’ve had iPods, CDs, and cassette tapes which we played using small Walkmans around the size of a cigarette box. And for a brief time before that, in the 1960s and 1970s, we had 8-track tapes. These were magnetic tapes housed in cases around the size of a large slice of bread. Car dashboards housed players, and they also came in a carry-around format like the one [Todd Harrison] recently bought at a Hamfest for $5 and made more portable by machining clips for a strap and adding a headphone jack.

But before hacking it, he wanted to try it out. Luckily his sister had hung onto her old tapes and after plugging it in and sliding in a tape, it worked! Opening it up he found that the contacts for the batteries were rusted but the mechanical components and electronics inside were very clean. Though he did add glue to a crack in the plastic read-head support, cleaned out some grease, did some lubricating, and cleaned the contacts in the volume control’s potentiometer. Check out his teardown video below for those details or if you just want to see how it all works.

Then came making it portable so that he could embarrass his kids by carrying it around the mall. The shoulder strap didn’t come with it, so he machined some clips out of steel and snapped on a strap. It didn’t have a headphone jack and he didn’t want to embarrass his kids too much, so he added one.  You can see that hack in the second video below, including how his repurposed jack automatically disconnects the speaker when the headphone plug is inserted. Personally, we think he looks pretty spiffy carrying it around wearing his Hackaday T-shirt.

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