Question Is it possible to modify the unit to allow the connection of an external cabinet  For example I would like to replace the driver with a 8 Ohm model and add an output to connect an external cabinet  Answer You cannot replace any parts or perform any design modifications that are not approved or proposed as option by TC Electronic 1. you will void the warranty if the unit is still covered. 2. Any modifications cannot be allowed by TC, because that would also cancel the safety conformity of the unit.  There is no modification option for the BG250 or the BG500.