Mini Guitar Bass Amplifier

Output power: 6W into 4 Ohm load, FET input stage - Passive Tone Control

Tiny, portable Guitar Amplifiers are useful for practice on the go and in bedroom/living room environment. Usually, they can be battery powered and feature a headphone output. This project is formed by an FET input circuitry, featuring a High/Low sensitivity switch, followed by a passive Tone Control circuit suitable to Guitar or Bass. After the Volume control, a 6W IC power amplifier follows, powered by a 12-14V dc external supply Adaptor or from batteries, and driving a 4 Ohm 10 or 13cm (4"/5") diameter car loudspeaker. Private listening by means of headphones is also possible.

Circuit diagram:

Mini Guitar-Bass Amplifier Circuit Diagram

Parts:

P1____________1M Linear Potentiometer
P2____________100K Log Potentiometer
R1____________68K 1/4W Resistor
R2____________470K 1/4W Resistor
R3____________2K7 1/4W Resistor
R4____________8K2 1/4W Resistor
R5____________680R 1/4W Resistor
R6____________220K 1/4W Resistor
R7____________39R 1/4W Resistor
R8____________2R2 1/4W Resistor
R9____________220R 1/4W Resistor
R10___________1R 1/4W Resistor
R11___________100R 1/2W Resistor
R12___________1K5 1/4W Resistor
C1____________100pF 63V Polystyrene or Ceramic Capacitor
C2,C5,C9,C14__100nF 63V Polyester Capacitors
C3____________100µF 25V Electrolytic Capacitor
C4____________47µF 25V Electrolytic Capacitor
C6____________4n7 63V Polyester Capacitor
C7____________470pF 63V Polystyrene or Ceramic Capacitor
C8____________2µ2 25V Electrolytic Capacitor
C10___________470µF 25V Electrolytic Capacitor
C11___________22nF 63V Polyester Capacitor
C12___________2200µF 25V Electrolytic Capacitor
C13___________1000µF 25V Electrolytic Capacitor
D1____________3mm red LED
Q1____________BF245 or 2N3819 General-purpose N-Channel FET
IC1____________TDA2003 10W Car Radio Audio Amplifier IC
SW1,SW2_______SPST toggle or slide Switches
J1_____________6.3mm Mono Jack socket
J2_____________6.3mm Stereo Jack socket (switched)
J3_____________Mini DC Power Socket
SPKR___________4 Ohm Car Loudspeaker 100 or 130mm diameter

Notes:

• Connect the output Plug of a 12 - 14V dc 500mA Power Supply Adaptor to J3
• Please note that if the voltage supply will exceed 18V dc the IC will shut down automatically

Technical data:

Output power (1KHz sinewave):
6W RMS into 4 Ohm at 14.4V supply
Sensitivity:
50mV RMS input for full output
Frequency response:
25Hz to 20kHz -3dB with the cursor of P1 in center position
Total harmonic distortion:
0.05 - 4.5W RMS: 0.15% 6W RMS: 10%

Tone Control Frequency Response:

Source : www.redcircuits.com

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Mini Metronome

Linear scale-Small size 40 to 208 beats per minute

Mini Metronome Circuit diagram:
 

Notes:

• Q1 & Q2 provide linear frequency operation of IC1 following P1 resistance variation.
• Q3 was added in order to obtain a louder click, similar to clockwork metronomes.
• 12V micro battery was used to obtain more output power and more compactness.
• Rotate P1 fully towards R2, then set R1 to obtain 40 beats per minute (compare with another metronome).
• Rotate P1 fully towards R3, then set R4 to obtain 208 beats per minute.
• Finally mark the entire scale with the usual metronome steps as following:
• 40 - 42 - 44 - 46 - 48 - 50 - 52 - 54 - 58 - 60 - 63 - 66 - 69 - 72 - 76 - 80 - 84 - 88 - 92 - 96 - 100 - 104 - 108 - 112 - 116 - 120 - 126 - 132 - 138 - 144 - 152 - 160 - 168 - 176 - 184 - 192 - 200 - 208.

Parts:

P1______100K   Linear Potentiometer
R1_______10K   1/2W Trimmer Cermet
R2_______10K   1/4W Resistor
R3______330K   1/4W Resistor
R4_______50K   1/2W Trimmer Cermet
R5______100K   1/4W Resistor
R6,R7_____1K   1/4W Resistor
C1________1µF   63V Polyester Capacitor
C2_______10nF   63V Polyester Capacitor
C3_______47µF   25V Electrolytic Capacitor
IC1_____NE555   General purpose timer IC
Q1,Q2___BC560   45V 100mA Low noise High gain PNP Transistors
Q3_____ZTX753   100V 2A PNP Transistor
SW1______SPST Switch (Ganged with P1)
SPK______8 Ohm 40mm. Loudspeaker
B1_____12V Battery (MN21, GP23A or VR22 type)

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