| 摘要 |
PURPOSE:To prevent electromagnetic noise from being reproduced as sound by processing a frequency characteristic of a regenerative signal variably in response to a volume control signal and applying the processed regenerative signal to a main amplifier means. CONSTITUTION:A tone controller 5 being a component of a preamplifier adjusts the frequency characteristic of a regenerative signal by the manual operation or based on a tone control signal. Then the regenerative signal amplified by a volume controller 6 is fed to a main amplifier 7 being a main amplifier means via a filter 9 being a frequency characteristic variable circuit. In this case, the control over the filter 9 by the volume control signal is activated when the volume control signal sets the amplification factor of the volume controller 6 to be less than a prescribed amplification factor and inactivated when the volume control signal sets the amplification factor of the volume controller 6 to be more than a prescribed amplification factor. |
