R2 of OpenGen has been going well so far. I have made plenty of changes:

• I will need a four-layer board for the fast analog parts, which provides easier power supply routing and much better grounding. However, they're expensive and I don't need one for everything else (control and peripherals), so there will be a larger (and cheaper) two layer board connected to the 4-layer one by a board-to-board interconnect.
• The power supply rails now work as follows:
  • ±12V: powered by two low-dropout precision voltage regulators (LT3090 and TPS7A4501), runs from ±13V;
  • ±13V: powered by a dual switch-mode power supply controller (LT3471) which provides high efficiency;
  • 5VD: powered by a TPS62160 switch-mode power supply controller which provides 92% efficiency (according to TI's WEBENCH);
  • 5VA: powered by a low-dropout precision voltage regulator (TPS7A4901).
• The amplitude and offset adjustments for the sine output and the duty cycle adjustment for the square output will now likely be 8-bit resolution rather than 12-bit as they will be taken from the microcontroller's PWM outputs.
• I will add a battery low indicator light (6.2V) and a FET switch that shuts down the device when the battery is critically low (6V). The FET will initially be set high by a 'soft' power button and from then on by a comparator. When the battery drops below 6V, the FET shuts off and the user must charge the battery to make the device stay on when they press the power button.
• There will be some changes to the output stage to allow it to provide ±10V at 42.5MHz (the THS6022 did not have a high enough slew rate). Exact changes TBC.
• I will add two load-disconnect switches (one for each output channel). These will control latching relays on the outputs of the op-amp and comparator. There will also be an 'active' LED for each channel. This indicates whether there is an output which can be connected, i.e., whether the channel is disabled in software (and therefore in a low-power shutdown state). If both channels are disabled in software (by the user or at startup), the analog supply rails will go into a shutdown state to save power.