SQPB - what is it?

[DVtyro]

From "VCR troubleshooting & repair" by Capelo, Gregory R; Brenner, Robert C

Presently, only metal heads can be used to record on metal tape. Ferrite heads can play back a prerecorded signal from metal tape, but cannot record on the metal tape.

This does not apply to SVHS though, as SVHS tape is cobalt-doped ferric tape (BASF also offered chrome tape), so it is basically Type II tape in audiocassette terms. It it is known that cheap audiocassette recorders meant for Type I tape only did crappy recordings when Type II tape was used.

[ARC Tech-109]

Has to do with the actual magnetic energy and saturation of the head material itself as ferrite saturates at far lower levels than it takes to actually imprint a metal based tape. Cassette technology also requires a far higher bias and signal drive to record on a metal tape be it ME or MP formulation.