Hi All,
Early Nov development update.
Overall things are finally coming together on the V4 development front and we are on track for releasing the V4 before year's end. But there's always something. I noticed that when I upped the gain to 12 dB on the buffer module, that there was a noticeable low level hum coming from the speakers. That started a search for the cause. After challenging every aspect of the buffer board design, and the V4 board itself, the ultimate cause of the noise was the OLED display. Essentially the same OLED display I've been using for several years now. Turns out the hum was always there but it wasn't until the buffer board amplified it that it became an audible issue. I'm actually a bit perplexed that I hadn't noticed this sooner.
So I took a deep dive into the OLED display itself and discovered that the OEM controller for the display, which runs off of 3.3 volts from the V4 board, has its own dc-dc switching boost converter that generates 12 volts used internally to refresh the OLED display screen. This converter is the cause of the 100-200 hertz noise. Turn off the OLED display and the noise goes away completely because this converter turns off as well. After evaluating corrective options, I'm going to add an isolated power converter to our OLED interface board. The isolated power converter converts 3.3 volts into 3.3 volts with its own independent ground separate from the V4 itself. This will prevent any OLED noise from traveling upstream into the V4 controller and the buffer board (if one is present).
This will require one more iteration on the OLED adapter board design which will likely take until mid-November before I have updated hardware on hand and am able to test out the fix.
Aside from this issue, the V4 board design is done and I have production blanks on hand already. I may tweak the buffer board and linear power supply board designs slightly and order updated blanks on those too while we wait on the OLED adapter updates.
Almost there,
Morten
