The KL2 was SF's first entry in the dedicated LED heads, to my knowledge. It uses a current limiting circuit which is like a "smart" resistor; excessive voltage is chopped off and spent as heat. Unfortunately, the LED's only require 6 volts so with a 9 volt supply, the third cell is basically spending its energy as hand warmer. In the case of the M6, two of the cells are relegated to hand warmer mode. With the KL6 however, all of the cells will be working for a united cause of photon creation with the thermal output solely a result of the inherent inefficiencies of the LED.
- Don