Apparatus and instruments for recording, amplifying and reproducing sounds; sound processors, amplifiers, preamplifiers, power amplifiers; buffers, distributors, signal generators and convertors, all for use with audio signals, video signals or combinations of audio and video signals; video, audio and video and audio signal testing, monitoring, recording and reproducing or processing apparatus, namely, signal testers, monitors, signal generators, analyzers, video tape players, switchers, rout...