Bill Erickson asks, “Is it safe for me to use my current 13.8 v power supply on a ubitx, or do I need to pick up a 12 v 5a version?”
The answer is probably. Many constructors have been using 13.8v supplies with the µBITx and the BITx40, and quite happily over a reasonable period of time. The parts are generally rated to cope with 12v nominally, but this typically means up to around 14-16v.
There are components in the µBITx, however, that will not cope with more than 15v. Some capacitors are 16v rated. A component that is rated at a maximum voltage of 15v is the TDA2822.
Those of you with a WX version of the TDA2822 should be using a voltage regulator to reduce the voltage to 9v or less on this chip. The chip is, otherwise, bound to fail. Those with the FCI version needn’t worry so much, but may want to current limit (with a resistor) the output of the audio stage into speakers/headphones.