Assertion: amplifier's feature | /r/CapableOf | become available
Facets:
value: about this time
type: TEMPORAL
Source sentences:
text: About this time, the "Top Boost" (or "Brilliance") feature became available as Vox's optional addition of a rear panel-mounted circuit that introduced an extra gain stage and tone controls for bass and treble (as opposed to the single "tone" control of earlier AC30s).