DÆ Remote
I received the printed circuit board for the remote and had time to populate it. I also had time to advance the firmware to a near final version. I received the laser cut acrylic top and bottom but I am still waiting for the 3D printed covers. I should have the covers by the end of the week and will add a better description to the DÆ Remote product page when I get that far.
I am very happy with the results. It looks so cool that my wife wants one even though she doesn’t need it. High praise in anybody’s book. Actually she asked if I can turn the industrial design into a phone. Another future project?
The remote uses capacitive touch technology so the main body is only 6 mm thick! Using proximity sensing it lights up when you go to pick it up. Turns out this is a fun feature in a brightly lit room but really works well in a dimly lit room; and a lot of serious listening in done in a dimly lit room. The remote has a light sensor so the intensity of the back light is tailored to the ambient light in the room. This seems like a small detail but I need to add it to my pre-amp design because the indicator lights on the pre-amp are good during the day but far too bright and distracting in lower ambient light. The lithium battery is charged by plugging the remote into a USB port. I expect the remote will run for a few months on a single charge.
The remote is coming together.
Vacuum Testing, Vacuum Testing and More Vacuum Testing
I think I have now solved all my major design issues with the glass vacuum chamber. The sleeve valve, improved cable feed through and absolute vacuum sensor all work well. The absolute vacuum sensor is on the PCB inside the vacuum chamber in the picture below. Using this sensor, I can draw a vacuum through the sleeve valve, close the sleeve vale and plug its port while still getting a vacuum measurement. This design eliminates the external vacuum tubing which is a potential source of leaks.
I have now tested for almost a month with very, very little pressure change. Maybe only the small amount of off-gassing from the components is contributing to the tiny decrease in vacuum I can measure. The absolute vacuum sensor saturates as all the air is evacuated and the leak rate is now approaching the limit of what I can measure. Perhaps it is time to add a “getter” material for the next bit of performance improvement.
Long-term vacuum testing including glass enclosure, sleeve valve and absolute vacuum sensor.