Multifunctional digital reverb circuit (b)

Figure 5-27 is a multi-functional digital delay reverberation circuit composed of M50195 as the core. The whole circuit mainly
consists of two parts: a multi-channel microphone input circuit (a) and a digital delay circuit (b).
    Multi-channel microphone input circuit (a) o The multi-channel microphone input hybrid circuit is composed of XII Mi532, with a total of three stages of amplification, of which
Icl constitutes a three-channel microphone input preamplifier, plus an FM microphone input. ICla is used as MICi input preamplifier, and
its input resistance value is relatively large (20kfl). It can be used as either a high-impedance microphone (10kfl) input or a low-impedance microphone (600tl) input
. It has greater flexibility in use. The volume of the microphone input is adjusted by a super dynamic low-noise Gm volume adjuster composed of RPt . This volume adjustment method not only allows the circuit to have a larger dynamic range, but also avoids the potential loss
due to the input signal not passing through
the potentiometer . The friction noise caused by poor contact of the amplifier can be eliminated, and the ordinary potentiometer o
    op amp IClb can be used as the preamplifier for the two microphone inputs of MIC2 and MIC3. The two input signals are mixed at the non-inverting end
. This input amplifier is designed for low-impedance microphone input, so the input resistance value is small. When there is only one microphone input
, the input socket of the other input will automatically ground the input end. The volume of the two microphone inputs is controlled by RP2.
    The input of the microphone is connected to the inverting terminal of ICla through a 39kfl resistor. When using a wireless microphone,
the audio output terminal of the FM radio is connected to this input terminal. The FM input terminal can also be used to listen to FM radio. It also has
a digital delay function. The chat input can also be connected to the inverting input terminal of IClb. The connection method is the same as that of ICla.
    IC2a ​​is an inverting hybrid amplifier for each microphone input signal, with a gain of about 15 .
    IC2b constitutes a parametric tone controller, which is characterized by a variable frequency compensation point, which
can ' sound defects during singing. The high and low bass adjustment potentiometers adopt dual-connected synchronous adjustment potentiometers. , when the double-connected
potentiometer is turned left, it increases the bass, and when it is turned right, it increases the treble. The center frequencies of the treble and bass compensation are 200Hz and
3.5kHz respectively, and the amount of improvement and attenuation is 15dB. Frequency components below 030Hz and above 15kHz are basically unchanged. The output signal
One channel directly enters IC3 for mixing, and one channel is input to the delay circuit for delay processing. The I island constitutes a hybrid amplifier, which
can mix the main signal of the microphone and the delay signal as well as the accompaniment music signals of the R and L channels according to a certain proportion and then output. Input
amplifier circuit .