First built late 2024. It has speaker protection circuit (crowbar type) on the main PCB as standard.
This PCB uses voltage references the control the main constant current sources. The capacitors in the signal path are the very low impedance polymer type which also have better longevity. The bias current is now controlled by a high quality multi turn preset potentiometer which makes it more precise and highly unlikely to shift in its setting . There is a new clipping detector circuit which is not susceptible to thermal drift and is sensitive to extremely short clip durations.
Should the PCB fail and produce DC, the speaker protection device will short the output to ground. This will involve very high short term current which will flow via the power ground wire back to the PSU. This wire needs to be able to easily blow a 5A fuse and I recommend at least 16/0.2 gauge wire.