Question Does the built-in tuner on the BH/BG bass head / combos only work for standard tuning For instance, let's say I wish to detune all the strings a half step, can I then use the built-in tuner of the BH500 to do so, or would I need to buy a separate tuner

The built-in tuner of the BG / BH amps only works with standard tuning and a single reference: A = 440 Hz. If you need to detune all strings or if you need another reference (i.e. 442 Hz) you will need to use a separate tuner.