Built to professional standards. Advanced Industrial grade high capacity valves not used in any domestic amplifier. EAR amplifiers proven in studio use. Accurate simple self-biasing for user replacement of valves when appropriate. In professional applications XLR input connectors and balanced semi-floating inputs are supplied at a nominal additional cost. Stability - No feedback is used on the transformer secondary - The amplifiers are entirely stable into any load. Matched mono amplifiers are supplied in pairs for stereo.