Adding An Audio Jack To Classic Headphones Is A Nifty Upgrade

One of the most common ways to junk a pair of headphones is to damage the cord. Obviously, the lead can be repaired, but it involves busting out the soldering iron and can be tedious when dealing with the tiny little coated wires.

It does involve soldering, but ideally, you only have to do it once.

[] has a way of dealing with the problem in a once-and-done fashion, by installing a female audio jack into his vintage headphones. The benefit is that if the cable is damaged, it can simply be unplugged and replaced with a new one, and is commonly seen on headphones from companies like KRK. 

The hack is simple when applied to a classic pair of AKG K141 headphones. The little plastic casing on one earpiece is popped off, and replaced with a 3D-printed version that stoutly holds a female TRS jack in place. This can then be soldered up to the wiring inside the headphones.

With everything assembled, the headphones can now use an easily-replaceable cable, and one needn’t worry about having to bust out the soldering iron if the lead is damaged in future. It’s a particularly useful hack for those who use their headphones on the road, always throwing them into backpacks between gigs.

If that’s not hardcore enough, consider attaching a headphone jack to an old 8-track player for the most ridiculous Walkman you can imagine. If you’ve been working on your own portable audio hacks, be sure to drop us a line!

The TRS80 Model 100 Gets A Brain Transplant

We’ll forgive you if you were busy in the ’80s, and missed the TRS80 Model 100. It was a portable version of the original, ran on four AA batteries, and even had an integrated acoustic coupler which proved handy for workers on the go. However, time is rarely kind, and [Trammell] had come across a non-functional example for just $20. It was time to bring this relic screaming into the modern age.

The motherboard was toast, so [Trammell] decided to wire up a Teensy++ directly to the Hitachi HD44102 display driver chips. Being an older LCD, the display needed a negative bias voltage, so a few diodes, capacitors and a PWM line stepped in to create a charge pump. There was no character generator on board, so the heavy lifting is all handled by the Teensy itself. The keyboard was a simple enough matrix design, so that was wired straight up.

[Trammell]’s work with this iteration got as far as acting as a USB serial terminal, and there was some work done on VT100 emulation. However, according to Twitter, the next stage involves an iCE40 FPGA and some music with which we’re altogether too familiar.

[Trammell] owns a working Model 100, too – employed in some modem experiments, no less.

MIDI Association Releases Spec For TRS Jacks

The MIDI spec was released in 1983, and for more than thirty years every synthesizer, drum machine, and piece of computer hardware with MIDI has sported an enormous DIN-5 jack on the back. Why did they choose such a large connector? Well, MiniDIN connectors hadn’t even been invented yet, and today even MiniDIN connectors are rarely-seen, obsolete connectors.

In the last decade, MIDI has found its way into some very small machines. Those Pocket Operators have MIDI sync, you can control a Game Boy with MIDI using the right hardware, and the cute little Korg synths also have MIDI tucked away in there somewhere. You can’t put a DIN-5 jack on those things, leading to some weird implementations of MIDI over non-standard connectors.

Now the MIDI Association has weighed in on the situation. There’s now a spec for MIDI over 2.5mm and 3.5mm TRS jacks. In just a few short decades, you’ll be able to connect MIDI gear with an audio aux cable.

Although there are five connectors in a DIN-5 jack, most implementations use only two connectors to send and receive data. Synth manufacturers have capitalized on this fact and cheap TRS connectors to build their own implementation of MIDI using smaller connectors, sometimes with incompatable pinouts.

Now, though, there’s a standard. For TRS connectors, the tip is pin 5 on the DIN-5, the ring is pin 4, and the sleeve is pin 2. It sends and receives data to synths and drum machines from 1983, and it doesn’t use gigantic connectors.

The only caveats to the new MIDI standard is that 2.5mm TRS connectors are recommended, and that protection circuitry is strongly recommended in the case a headphone driver is inevitably connected to a MIDI device. Other than that, everything’s coming up roses, and this opens up the door to MIDI jacks that are much, much easier to source.