Charliexu - I have made the upgrade to several units. It updates the functionality of the pre-amp regarding battery / AC mode as well as the various status modes indicated by the center light. The issue was with the batteries retaining their charge, not the design of the machine. Selecting the AC mode will fully recharge the batteries and the user now has the ability to select between battery or AC.
When used in AC mode, the sound is close to battery mode because the power is supplied by the external power supply through the batteries. The AC grunge, while not fully removed, will be well filtered out thanks to batteries damping action.
I'm sure your dealer has all the details.
When used in AC mode, the sound is close to battery mode because the power is supplied by the external power supply through the batteries. The AC grunge, while not fully removed, will be well filtered out thanks to batteries damping action.
I'm sure your dealer has all the details.