There are preamplifier with four inputs

  
Figure 3-25 is a hybrid having four input preamplifier, in the circuit, cZ1, cz, C23 and cz4 respectively, can enter the microphone, line, phono and crystal head signal. Quad c
There are preamplifier with four inputs - schematic

an enter individually or simultaneously four mixed input, but also for dubbing the program needed chipped commentary and other editing. Enter either alone or in combination input, nothing happens to them between each other. The preamplifier input is applied the principle of proportional adder inverting operational amplifier, when several signals simultaneously input Pops, the output voltage is equal to the sum of each of the input voltage. While at the inverting input of the operational amplifier summing point of virtual ground, and therefore between the respective input signal is isolated from each other when the input signal is a road 0:00, the input voltage across the resistor is also zero, so it does not affect the work of other separate ways o to accommodate each source input voltage is different, four input interface uses a different structure and number of circuit elements value, while also adding additional input required. The input interface circuit component values are shown in the diagram in accordance with the subject of the input signal sensitivity calculations. If the actual figure depending on the input with the standard values can be properly adjusted R2, R, R6, or where the resistance can be. When C24 as head input, Ra take 1kfl, thus attenuating the treble, treble end of the play frequency equalization effect o volume control potentiometer RPi and Rl1, C treble consisting of automatic compensation circuit; RPi and Rt2, c9, Rl3 form a low tone automatic compensation circuit. When RPl turn up the volume the more hours, the larger the amount of compensation Pak compensation circuit, therefore, adjust the sound volume when, without resetting the pitch controller.. SA control switch for the compensation circuit. RC network composed of five sections of the equalization circuit, adjust the range of 12dB. czJ and C24 high sensitivity, large-amplitude signal can not accidentally access lines, etc., so as not to damage the amplifier overload and bad. No C24, the commissioning should point J disconnected. In order to reduce hum and induced noise, (: zl ~ C24 and an input element should be shielded metal cover, and good well grounded input signal line should be used in all metal shielded wire, and the end is well grounded. Circuit adoption of better performance quad op amp TL084, has good frequency response of the input line, the passband bandwidth of approximately 20Hz ~ 20kHz, distortion 0.5% o




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