A pressure compensator assembly is deployed in a servo-driven mud pulser. The assembly includes a generally tubular compensator sleeve that expands and contracts in a radial direction in order to compensate for pressure differentials across the compensator sleeve. A thrust bearing arrangement is also deployed in a servo-driven mud pulser, the thrust bearing arrangement designed to protect the servo motor from reactive energy caused by servo motor stalls as the motor changes direction of rotation. A torsion bar is deployed in a drill string to protect fragile components and electronics in the drill string by absorbing and smoothing out torsion spikes in the drill string arising from stick-slip events.