Electric Guitar/Violin Preamplifier


Posted on Feb 6, 2014

Magnetic pick-ups in musical instruments have a relatively high output impedance. This can result in a reduction in treble response when connected via a long cable run or to equipment with a low input impedance. This preamplifier provides a high input impedance and a low impedance output, solving both issues. It has adjustable voltage gain and can


Electric Guitar/Violin Preamplifier
Click here to download the full size of the above Circuit.

run off a battery or DC plugpack. The input signal is AC-coupled to the non-inverting input of IC1a, part of a TL074 quad op amp. This has JFET input transistors and the input impedance is set by a 330k © bias resistor which also sets the DC level at this input to half supply (Vcc/2). This is generated by a voltage divider comprising two 10k © resistors and bypassed by a 47 µF capacitor to reject noise and hum. IC1a is configured as a non-inverting amplifier with a gain of between 2 and 20, depending on the setting of VR1. IC1a`s output is fed to VR2 via a 22 µF capacitor, allowing the output volume to be set. The audio then passes to the non-inverting inputs of the remaining three op amps (IC1b-IC1d) which are connected in parallel to provide a low output impedance; it will drive a load impedance as low as 600 ©. The 100 © resistors in series with the outputs provide short-circuit protection for the op amps and also prevent large currents from flowing between the outputs in case they have slightly different offset voltages. The buffered signal is then AC-coupled to two output connectors using 47 µF electrolytic capacitors. For Output 1, a 47k © resistor sets the output DC level to ground and a 220 © series resistor provides further short-circuit protection. Output 2 is similar but includes another potentiometer (VR3) to allow its level to be set individually. Note that this means the impedance of Output 2 can be high (up...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Mike Pads
    DC-10Khz frequency-voltage converter
    Simple Utility Mixer
    A Simple Sine Wave Oscillator
    Fog Lamp Sensor Circuit
    current mode amp powers 24 ghz
    miconghs
    DC Chopper control vs Phase Angle control
    remote control sckt
    Classic 8051 Memory Layout
    ultrasonic transmitter
    12V-220V Modified Sine-wave Inverter Circuit
    Multi-functional 100W Power Inverter with 5V USB
    Tube amplifier input voltage input



    Top