Recently, we found an old Logitech Pure-Fi Express Plus that had been laying around from old times. It was originally made for docking a iPod / iPhone with the old Apple 30-pin Dock Connector. Since this connector is pretty obsolete, there’s no need for that anymore.
No Bluetooth? In 2017?
However, the unit still has a separate AUX connector, but cables are annoying when you deal with a portable speaker. Therefore it would be perfect if we could easily add Bluetooth to the device. Indeed the unit does not have the best sound quality, but as a portable speaker it does a decent job. And as long the Bluetooth modification was quick, we still figured out it was worth it.
Previously we’ve had good experience with the Qualcomm CSR8645 chipset implemented on a breakout board from China / eBay. So how do we connect it to our Logitech speaker? Let’s start with a quick search for the Apple Dock Connector pinout. And the “good old” pinouts.ru give us the answer.
From the pinouts.ru table we can see that we have the analog audio lines, ground and several data / power signals. This is good news since we can attach our Bluetooth module directly without any conversion. We brought out our soldering iron and soldered analog audio and power lines between the Bluetooth module and the Logitech Dock Connector PCB.
Thereafter we applied some glue to stick things in place.
We also added some insulation tape around the PCB board to ensure that nothing will short out inside the speaker.
Luckily, we could place the module back into the speaker without having the Dock Connector in it’s original location (unavailable for the user).
Finally, we mounted the back cover again. As you might notice we have also added an extra power switch. This is wired inline with the battery pack so that the pack can be disconnected from the electronics.
The original design made by Logitech is really terrible. When you operate it by battery power (i.e. at all times when batteries are inside the speaker) the electronics doesn’t really turn off. The amplifier circuit does turn off, but none of the power regulators, LEDs or other circuitry turn off. This leads to a terrible “not in use” battery life with the consequence of higher consumption of batteries.
With this quick Bluetooth fix we are able to extend the speakers lifetime with at least a couple of years, in addition to the benefit of wireless music streaming and the enhanced idle power consumption.