Aug 082020
 

So, lately I’ve been working from home, which means amongst other things, playing music as loud as I like, not getting distracted by co-workers, and the kettle a short walking distance from my workspace.

Eventually though, I will have to return to the office. For this aim, I’ll need to be able to “drown out” the background noise. Music is good for this, but not everyone is into the same tastes as I am — I am a bit of a music luddite.

Years ago (when the ink was drying on my foundation license) I purchased a Logitech Wireless headset. Model A-00006 (yes, that is quite old now). This headset worked, but it did have two flaws:

  1. the audio isolation wasn’t great, so they tended to “leak” sound
  2. they had the dreaded asymmetric audio sample rate problem with JACK.

Now, for home use I bought a much nicer set which solves issue (2) and isn’t too bad with (1), but I’d like to keep them home. (2) isn’t a problem at work since I don’t generally have the need for the audio routing I use at home. So (2) isn’t going to be a problem.

This headset sat in a box for some years, and over time, the headband and earpads have fallen to bits. The electronics are still good. What if I bought a pair of earmuffs and stuffed the old headset guts inside those? That’d solve issue (1) nicely.

Getting inside

These things didn’t open up without a fight. I found that where the speakers are concerned, you will permanently break the housing. The two sides are joined by a 8-wire ribbon cable. The majority of the electronics is in the right-hand side. The battery is most of the guts of the left side.

You’ll need to destroy the headband to liberate the ribbon cable, and you’ll need to destroy the speakers’ housing to get at the screws behind.

I now have the un-housed headset guts sitting on the table, with the original charger plugged in charging the very flat battery, which is a single-cell 3.7V LiPo pouch cell; no idea what capacity it is, I doubt it’s more than 200mAh.

Charging

I plugged everything back together and tried the headset out. It still works, although instead of indicating a solid amber LED for charging, it was showing a slow blink.

fccid.io has a copy of the original documentation online, as well as photos of the guts here. In that, it did not discuss what a “slow blink” meant, which had me concerned that maybe the battery had been left too long and was no longer safe to charge.

Battery voltage whilst charging is sitting around 4.2V, which sounds fair for a 3.7V cell. It eventually stops blinking, going solid, but then the other LED turns RED. Disconnecting the battery reveals 0V across the pins.

So I might be up for a new battery, the PiJuice batteries look to be a similar arrangement (single cell with termistor pin) and may be a good upgrade anyway.

Next steps

I prefer the microphone on the right-hand side, so that’s one thing I’ll be looking at changing. The ribbon cable connects using small FPC connectors, so I’m thinking I might see if I can de-solder those and put a beefier 2.54″ KK-style connector in its place. This will require soldering some wire-wrap wire up to the pins, but the advantage is it’s a much easier connector to work with.

The break-out board on the left side is very simple, no components other than a momentary switch for detecting the microphone boom position, and pads to which the left speaker, microphone, mute LED and battery connect. I’ll still put the battery in the left side, so there’ll still be 5 wires running across the headband. It should be easier to interface with a new battery as well doing this.

I will also have to bring the buttons and switch out to the outside of the earcup, so I’ll probably use KK connectors for those too. The power switch is a through-hole part, so that should be easy.

I’ll probably replace the proprietary power connector with a barrel jack too. Not sure if these will charge from 5V, the original charger has a 6V output.

I think once I’ve got more hacker-friendly connectors onto this, I should be able to look at readying the new home for the electronics.