Hearing sense actuator (a) composed of NE571

The hearing exciter composed of NE571, the circuit is mainly composed of audio exciter and signal controller
.
    Figure 5-15(a) is the main part of the circuit - the audio exciter part, where NE571 is used as a nonlinear harmonic
generator. Its principle can be explained by one channel: after the audio input signal is buffered and amplified by cl-Ri input IC2A, it
is divided into two channels, one channel is sent to the input end of the IC2B mixer, and the other channel is sent to the center frequency adjustable circuit composed of IC3A
The band-pass filter can make the center sampling frequency continuously change between 2 and 10 kHz through the adjustment of RPi. The sampled audio
components are sent to the nonlinear harmonic generator Icl, where they are divided into two channels. One channel is directly used to generate odd and even
harmonics, and the other channel is rectified and filtered and used as a voltage control signal to control the harmonics. The generation of the wave has nothing to do with the level of the input signal.
Since the internal operational amplifier of NE571 has poor transient characteristics and high noise, the external operational amplifier NE5532 is used
to compensate for this. The signal amplified by the external op amp rqB is sent to IC2B. The mixing amount is controlled by pin 2 in the middle, and is finally
mixed and output by IC2B.
    Figure 5-L5(b) is the signal control part of the circuit. Among them, IC201 (four-D flip-flop CD40175) and IC202 (four-two
NAND gate CD4011) form a two-position interlock switch to select the input of the signal source. IC203 (double D flip-flop CD4013) constitutes
a self-locking switch, which is used to control the on and off signals of the actuator. Three LEDs are used to display working status. SBi~SB3 are
light-touch selector switches. In
    the circuit , J) J is the sampling frequency selection potentiometer, used to select the excited music frequency band; J) 2 is the mixing amount adjustment
potentiometer, used to adjust the mixing of odd and even harmonics with the original input music signal. quantity. In actual use, generally for
vocal music, fo should be adjusted to around 3klh, for string music, it is better to adjust it to about 4.5kHz, and for wind instruments and some percussion instruments
, it should be adjusted a little higher.