An interesting upgrade for this circuit was suggested by Mike Baum, NY USA. This involves the use of a Lithium Ion Prismatic Rechargeable 340948 Battery, featuring a nominal voltage of 3.7V and a current rating of 1200mAH.
Parts:R1_____________10K 1/4W Resistor
R2____________100K 1/4W Resistor
R3_____________68K 1/4W Resistor (see notes)
R4______________1K5 1/4W Resistor
R5______________3K3 1/4W Resistor
R6____________330R 1/4W Resistor
R7______________4K7 1/4W Resistor
R8______________2R2 1/4W Resistor
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C1______________1µF 63V Polyester Capacitor
C2____________100µF 25V Electrolytic Capacitor
C3____________470µF 25V Electrolytic CapacitorQ1____________BC239C 25V 100mA NPN High-gain Low-noise Transistor
Q2____________BC337 45V 800mA NPN Transistor
Q3____________BC327 45V 800mA PNP TransistorJ1____________Stereo 3mm. Jack socket
SW1___________SPST Switch
B1____________3V Battery (two 1.5V AA or C cells in series, but see Notes)
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