New: Completely Assembled and Tested Designed to replace the STK-0050 in the Pioneer SX-780 and other Japanese stereo receivers and Integrated Amps using the old Sanyo module. Have been successfully used in Pioneer, Fisher, Technics amps and receivers. The list is growing. Generally can replace the STK-0050II as well Eliminates the probability of poor quality modules, improves reliability and performance Discrete design allows for easy service and long term reliability improvement You can use this design to replace STK-0040,0050,0070,0080,0105,0025,0029,0039 Specialized tooling and skills are required in order to install this module. Prior Audio Electronic knowledge and interpretation is helpful. Will ship International Note:  Listing is for two fully assembled & tested modules with attached heatsink, some thermal compound Free support but no returns. We will fully support our sales. The modules will improve the amplifier's reliability and operational specifications for amplifiers using similar STK modules, up to 75 watts.  Outputs transistors are OnSemi 200W devices. There is another listing for the same item using 150W Toshiba devices for a lower cost Output transistor bias adjustment is part of the circuit design. This allows for the modules to be adjustable for matched performance. Expected Performance: Total Harmonic Distortion: ~0.02% ( 20-20KHz,4-8 ohm, 31mA bias) Typ -93dB (~0.002%) THD, 8-ohm Gain (based on Pioneer SX-780 design) = 15.5 (23.8 dB) Bias: Each emitter resistor in the SX-780 are 0.22ohm, that would be 0.22 *0.031A =7mV across each emitter R or 14mV across the two of them. Increasing the bias current will make the output transistors to run hotter. This lowers the crossover distortion and allows for a larger class "A" operating region. Reference: Google: "STK-0050 Replacement for SX-780 and others" @ Audiokarma web site for additional details on our design.