The paper describes and interpretes some results of drop-out measurements on several recorder types with different signal processing (AC biased and FM), different tape drive and/or loading systems (open reel and cassette) and various tape material technologies (conventional, chronium and metal evaporated tapes). Mechanical and visual control (through an optical and a scanning electron microscope) of the surface of the tested tapes are added. In the field of the analog audio recording the tests were performed on a sophisticated audio drop-out measurement system. That gives the ability to draw a drop-out histogram and a three-dimensional plot of the tested audio recording system showing drop-out occurrence over length and depth of the drop-out. In a similar way, for digital audio recording on consumer VTRs, especially on VCR, the full drop-out statistics (of the video signal path) for strongly used and brand new tapes was measured and plotted for different systems and types of VTRs. In addition an equivalent circuit for a drop-out model on VTRs is given. These tests offer the ability to provide additional tape selection criteria considering the effect of length, depth and frequency of occurrence of drop-outs to the recorded information (analog and digital audio signals) and, on the other hand, a useful tool to define the end of the life time (with objective limits) for the tape material in use.
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