Whereas an electric guitar with 60W PMPO (Peak Music Power Output) costs around $8, here is a cost effective solution to convert a Hawain guitar to an electric guitar. The circuit can also be used as an ampli-speaker with a tape recorder or a radio receiver.
The unit can easily be assembled on a standard TBA810 ampli-speaker PCB available in the market. It is also be housed in an ampli-speaker box.
Do not try altering the single- transistor preamplifier and power supply stages, or you may end up with severe distortion and unwanted noises.
The circuit has been extensively tested and retested to the satisfaction of our musically-gifted friends. It has been tried successfully even with standard electric guitars.
Pick-up coil, the heart of the unit, is available in musical instrument shops as a ‘magnetic touch pick-up for Hawain guitars’. Its price varies from $1 to as much as $2. Only a good quality, high-gain pick-up should be used.
After assembling the circuit, for testing, switch it on and hit the pick-up gently with a screwdriver. The should produce some amplified sound.
After having tested it satisfactorily, you may place the pick-up coil of the unit below the strings of the guitar, about 2.5 cms away from the resonance hole, towards the bridge side of the guitar. Play the guitar and find out the optimum position for finally mounting the pick-up coil.
Always maintain sufficient distance between the guitar and the speaker to avoid feedback (a shrill sound). While operating on AC mains, ensure that a good earth connection exists, or else humming sound will be produced. This humming sound will disappear if you touch the chassis of the unit.
With the volume control at the maximum, the unit should give about 7 watts of noiseless PMPO.
Resistors (all ¼-watt, ± 5% Carbon unless stated otherwise)
R1 = 220 Ω
R2 = 560 Ω
R3 = 68 KΩ
R4 = 470 KΩ
R5 = 10 KΩ
R6 = 470 Ω
R7, R9 = 5.6 KΩ
R8 = 3.3 KΩ
R10 = 100 KΩ
R11 = 22 Ω
R12 = 100 Ω
R13 = 1 Ω
R14 = 1 KΩ, 0.5W
VR1, VR2 = 100 KΩ Linear
VR3 = 10 KΩ LOG.
C1, C4, C5, C7, C13 = 0.1 µF (Ceramic Capacitor)
C2, C3, C8, C9, C14, C16 = 100 µF/25V (Electrolytic Capacitor)
C6 = 0.01 µF (Ceramic Capacitor)
C10, C18 = 0.047 µF (Ceramic Capacitor)
C11 = 0.22 µF (Ceramic Capacitor)
C12 = 0.015 µF (Ceramic Capacitor)
C15 = 100 µF/16V (Electrolytic Capacitor)
C17 = 1000 µF/25V (Electrolytic Capacitor)
IC1 = TBA810
T1 = BC549C
D1, D2 = 1N4007
ZD1 = 6.3V, 1W, Zener
X1 = 230V AC Primary To 9V-0V-9V 600A sec. Transformer
SW1 = On-Off Switch
LS1 = 8Ω, 5W Speaker
LS2 = 4Ω, 10W Speaker