This paper describes a method of changing the time constant using gain control for playback equalizers and automatic level controller (ALC) of VHS VCRs using microprocessor-assisted processing. In the case of bipolar IC for a standard model, a total of 10 time constants which consist of external results of a VCR developed using this new method significantly reduced these time constants to 2. That is, it was confirmed that this method has an equivalent performance in frequency characteristics and recovery time to the standard model. Moreover, the attack time was shortened to 1/20 of the standard model, therefore the pop noise was decreased. The proposed method is suitable for system on a chip (SOC) using a BiCMOS process.
['Kunihiro Yamada', 'Masanori Kojima', 'Teruo Furukawa', 'Fumiaki Sato', 'Tadanori Mizuno']
Microprocessor-assisted audio signal processing system for VHS VCRs