This is a circuit for a guitar preamplifier that can accept any standard guitar receiver. It is also versatile in that it has two signal outputs. A typical example of using a guitar head-mounted microphone is shown in Figure 1. The microphone unit has a adapter and a jack connector. The jack can be plugged into the preamp circuit and then into the power amplifier system. A device that picks up mechanical vibrations, usually from stringed instruments such as a guitar or violin, and converts them into electrical signals, which can then be amplified by an audio amplifier.
It is usually attached to the body of the guitar, but can also be attached to the bridge, neck, guard or headboard. The first part of this preamplifier circuit shown in Figure 2 is a single-transistor common-emitter amplifier with degenerate feedback in the emitter and an initiating bias divider to ensure optimal input impedance. . With the component values shown here, the input impedance is greater than 50 kilohms and the maximum output voltage is approximately 2 V RMS. The main level control pot VR1 must be adjusted for minimal distortion. The input of the guitar receiver is sent to this preamplifier at the J1 connector. The signal is buffered and processed by an operational amplifier connected around the TL071 IC (IC1).
Adjust gain using the VR2 preset. The circuit has master and slave control. The J2 RCA jack is the main signal output jack and the J3 jack is the auxiliary jack. It is better to take the signal from J2 as the input of a power amplifier system or an audio mixer. The output signals from the J3 can be used to drive a standard headphone amplifier. Using the VR3 rheostat, adjust the level of the auxiliary output signal on J3. Place the circuit in the metal box. VR1 and VR3 should preferably be the one with a metal case. To avoid noise, ground the housing and housing. A well regulated 9V DC power supply is crucial for this circuit. However, a standard 9V alkaline manganese battery can also be used to power the circuit. Switch S1 is an on/off switch.