This is Modular Audio Preamplifier,high quality, discrete components design with Input and Tone Control Modules.The circuit consists of two module:Main module and tone control module.Features: Main Module Input sensitivity: 250mV RMS for 1V RMS output Tone Control Module Input sensitivity: 1V RMS for 1V RMS output Maximum output voltage: 13.4V RMS into 100K load, 11.3V RMS into 22K load, 8.8V RMS into 10K load Frequency response: flat from 20Hz to 20KHz Total harmonic distortion @ 1KHz: 1V RMS 0.002% 5V RMS 0.003% 7V RMS 0.003% Total harmonic distortion @10KHz: 1V RMS 0.003% 5V RMS 0.008% 7V RMS 0.01% [...]