Active filter control apparatus

In a recording/reproducing apparatus having a variable recording/reproducing speed and including an active filter having a variable cut-off frequency, the improvement comprising an active filter control apparatus including:

• means responsive to a control signal for tuning the cut-off frequency of the active filter;
• and
• characteristic correction means coupled to said tuning means and responsive to the control signal for generating a correction signal to correct a group delay characteristic of the active filter in accordance with a set cut-off frequency, wherein:
• said characteristic correction means includes correction signal generator means for generating the correction signal in accordance with a set correction amount from the control signal, and
• said cut-off frequency tuning means controls the characteristic of the active filter by using the correction signal.

A reproducing apparatus having different data reproduction speeds for different zones on a recording medium, comprising:

• a filter having a variable cut-off frequency, for processing read-out signals;
• a microprocessor operative to control the cut-off frequency of said filter in accordance with a table of correction factors for correcting a group delay characteristic of said filter, so as to control the group delay characteristic or said filter, said table being set in accordance with a zone of read-out data,
• correction signal generator means coupled to said microprocessor for generating a correction signal to correct the group delay characteristic in accordance with a set correction amount from the table;
• and
• cut-off frequency tuning means for controlling the characteristic of said filter by using the correction signal.

An active filter apparatus comprising:

• an active filter device having a variable cut-off frequency;
• means responsive to a control signal for tuning the cut-off frequency of said active filter device;
• characteristic correction means coupled to said tuning means and responsive to the control signal for generating a correction signal to correct a group delay characteristic of said active filter device in accordance with a set cut-off frequency, wherein:
• said characteristic correction means includes correction signal generator means for generating the correction signal in accordance with a set correction amount from the control signal, and
• said cut-off frequency tuning means controls the characteristic of the active filter device by using the correction signal.