Profile: Applied Research & Technology offers vacuum tube preamplifiers & compressors, microphones, graphic equalizers, power amplifiers and digital interfaces. Our SLA-4 power amplifier is a four-channel amplifier in a single rack-space that can be switched easily from multi-channel, stereo and bridged mono modes. Separate mode switches are used to bridge channels 1 and 2, or channels 3 and 4, or both channel pairs. This maximizes flexibility by allowing the amplifier to be configured for best utilization in 2, 3, or 4 channel applications. SLA-4 features SmartFanT, an advanced, thermal dependent fan assisted convection cooled system. The SmartFan system is dependent upon the internal ambient temperature of the unit, and runs at high or low levels depending on the amplifier's cooling needs.