This is a great sounding all FET (Field Effect Transistor) preamp featuring switching for six-line level inputs including tape monitor. Circuit highlights include a low output impedance which acts as a buffer between the level controls and the amplifier interconnect cables, avoiding the high frequency filter effect inherent in a passive control. This preamp has a unique zero-response circuit which exploits the symmetrical performance of N and P channel field effect transistors to cancel distortion without resorting to negative response. A low impedance discrete DC regulator powers this circuit, for minimum ac impedance at all audio frequencies. FET's are used in Sonographe audio circuits because of their tube-like square law transfer functions, which exclude unmusical odd order distortions that typify bipolar transistor circuits. Unit is in excellent condition. Owners Manual is included. * SMALL SURFACE SCRATCH. Below are some specs. Gain: 21dB Output: 10 V RMS Phase: Phase inverting. Response: 5 Hz to 100KHz Signal to Noise Ratio (20Hz-20KHz): 94 dB Distortion: less than .1% THD Output impedance: less than 200 ohms Dimensions: 12.25D x 17.125W x 2.5H inches Weight: 10 lbs