Guitar Control | EEWeb Community

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Stand-alone, 9V battery powered unit, Three-level input selector, three-band tone control

This preamplifier was designed as a stand-alone portable unit, useful to control the signals generated by guitar pick-ups, particularly the contact “bug” types applied to acoustic instruments. Obviously it can be used with any type of instrument and pick-up. It features a -10dB, 0dB and +10dB pre-set input selector to adjust input sensitivity, in order to cope with almost any pick-up type and model. A very long battery life is ensured by the incredibly low current consumption of this circuit, i.e. less than 800µA.

Guitar_Control_Circuit_Diagram.GIF

Parts:

P1,P2 – 100K Linear Potentiometers
P3 – 470K Linear Potentiometer
P4 – 10K Log. Potentiometer
R1 – 150K 1/4W Resistor
R2 – 220K 1/4W Resistor
R3 – 56K 1/4W Resistor
R4 – 470K 1/4W Resistor
R5,R6,R7 – 12K 1/4W Resistors
R8,R9 – 3K9 1/4W Resistors
R10,R11 – 1K8 1/4W Resistors
R12,R13 – 22K 1/4W Resistors
C1 – 220nF 63V Polyester Capacitor
C2,C8 – 4µ7 63V Electrolytic Capacitors
C3 – 47nF 63V Polyester Capacitor
C4,C6 – 4n7 63V Polyester Capacitors
C5 – 22nF 63V Polyester Capacitor
C7,C9 – 100µF 25V Electrolytic Capacitors
IC1 – TL062 Low current BIFET Dual Op-Amp
J1,J2 – 6.3mm. Mono Jack sockets
SW1 – 1 pole 3 ways rotary or slider switch
SW2 – SPST Switch
B1 – 9V PP3 Battery Clip for PP3 Battery

Circuit operation:

IC1A op-amp is wired as an inverting amplifier, having its gain set by a three ways switch inserting different value resistors in parallel to R4. This input stage is followed by an active three-band tone control stage having unity gain when controls are set in their center position and built around IC1B.

Technical data:

  • Frequency response: 20Hz to 20KHz -0.5dB, controls flat.
  • Tone control frequency range: ±15dB at 30Hz; ±19dB at 1KHz; ±16dB at 10KHz.
  • Maximum input voltage (controls flat):
    • 900mV RMS at +10dB input gain;
    • 7.5V RMS at -10dB input gain.
  • Maximum undistorted output voltage: 2.5V RMS.
  • Total Harmonic Distortion measured at 2V RMS output: <0.012% at 1KHz; <0.03% at 10KHz.
  • THD at 1V RMS output: less 0.01%
  • Total current drawing: less 800µA.

Stand-alone, 9V battery powered unit, Three-level input selector, three-band tone control

This preamplifier was designed as a stand-alone portable unit, useful to control the signals generated by guitar pick-ups, particularly the contact “bug” types applied to acoustic instruments. Obviously it can be used with any type of instrument and pick-up. It features a -10dB, 0dB and +10dB pre-set input selector to adjust input sensitivity, in order to cope with almost any pick-up type and model. A very long battery life is ensured by the incredibly low current consumption of this circuit, i.e. less than 800µA.

Guitar_Control_Circuit_Diagram.GIF

Parts:

P1,P2 – 100K Linear Potentiometers
P3 – 470K Linear Potentiometer
P4 – 10K Log. Potentiometer
R1 – 150K 1/4W Resistor
R2 – 220K 1/4W Resistor
R3 – 56K 1/4W Resistor
R4 – 470K 1/4W Resistor
R5,R6,R7 – 12K 1/4W Resistors
R8,R9 – 3K9 1/4W Resistors
R10,R11 – 1K8 1/4W Resistors
R12,R13 – 22K 1/4W Resistors
C1 – 220nF 63V Polyester Capacitor
C2,C8 – 4µ7 63V Electrolytic Capacitors
C3 – 47nF 63V Polyester Capacitor
C4,C6 – 4n7 63V Polyester Capacitors
C5 – 22nF 63V Polyester Capacitor
C7,C9 – 100µF 25V Electrolytic Capacitors
IC1 – TL062 Low current BIFET Dual Op-Amp
J1,J2 – 6.3mm. Mono Jack sockets
SW1 – 1 pole 3 ways rotary or slider switch
SW2 – SPST Switch
B1 – 9V PP3 Battery Clip for PP3 Battery

Circuit operation:

IC1A op-amp is wired as an inverting amplifier, having its gain set by a three ways switch inserting different value resistors in parallel to R4. This input stage is followed by an active three-band tone control stage having unity gain when controls are set in their center position and built around IC1B.

Technical data:

  • Frequency response: 20Hz to 20KHz -0.5dB, controls flat.
  • Tone control frequency range: ±15dB at 30Hz; ±19dB at 1KHz; ±16dB at 10KHz.
  • Maximum input voltage (controls flat):
    • 900mV RMS at +10dB input gain;
    • 7.5V RMS at -10dB input gain.
  • Maximum undistorted output voltage: 2.5V RMS.
  • Total Harmonic Distortion measured at 2V RMS output: <0.012% at 1KHz; <0.03% at 10KHz.
  • THD at 1V RMS output: less 0.01%
  • Total current drawing: less 800µA.

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