On The Inside

On The Inside

Monday, September 7, 2015

HeadBox On the Inside

HeadBox is the standalone version of SmartCans that I use for testing and development. It is essentially a stereo audio processor with a built in headphone amplifier. On the back it has inputs for power, stereo in and stereo out.

The inputs and outputs are 1/4" to match the majority of my audio gear. The front has just a headphone jack and volume control. Everything else is controlled over the network. The two clamshell halves separate easily and the boards life out of the bottom for easy access to all parts.

The edison can be seen on the far left on the other side of the pc-board separator. The sound card is on the inside next to the jack board. The headphone amp is mounted to the front panel.

Underneath the jack board is some power supply filtering circuitry. The back panel and support board for the Edison and the soundcard are made by simply soldering two blank pieces of pcboard material.

The construction remains solid because groves are cut into support bosses in the plastic so that when the clamshell is closed, there is very little movement.

Friday, September 4, 2015

An Overview of SmartCans Hardware

The Intel Edison is turned at an angle to allow for the USB connectors to fit while still allowing the earcup to be reassembled. While there is still some room available on the sound card side, unfortunately, there's not enough room there to squeeze in the power supply. In order to solve this problem, the power supply which consists of a battery charger module, a 600 mAH LiON batter and an inverter to supply the necessary 5V for USB power were embedded into the headband.

The yellow spacers around the ear cups were designed to expand the space within the earcup without compromising the mechanical integrity of the ear-cup. They are about 1/4" thick which allows enough room, however, the screw bosses are still able to mate with each other. Of course, longer screws were necessary to attach the two halves. With this method the spacers press solidly against the ear-cup surrounds and do not expand the headphones too much.

The matching yellow inserts in the ear-cups serve not practical purpose other than to fill in the unused space left from removing the volume control and to maintain visual continuity. 

Each of the PC boards were hand etched. Although not strictly necessary for a one off or prototype, the use of PC boards provides for greater reliability. These simple boards were laid out in ExpressPCB and hand etched. 

The cable extending over the headband carries USB, power, and the speaker audio for the speaker on the Edison side of the headphones. The next version of SmartCans will combine the sound card and Edison on one side of the headphones and include a higher quality headphone amplifier on the other side. 

USB really just gets in the way here. The right way to do this is to directly connect the DAC and ADC to the Edison. This would require a new host board for the Edison, or a larger headphone that could accommodate Intel's mini host board.