60W Guitar Amplifier Circuit
This is a circuit for the power amplifier, using a single-rail supply of about 60V and capacitor-coupling for the speaker. This is the figure of the circuit;

 

The advantages for a guitar amplifier are the very simple circuitry, even for comparatively high power outputs, and a certain built-in degree of loudspeaker protection, due to capacitor C8, preventing the voltage supply to be conveyed into loudspeakers in case of output transistors' failure. The preamp is powered by the same 60V rails as the power amplifier, allowing to implements a two-transistor gain-block capable of delivering about 20V RMS output. This provides a very high input overload capability. The value listed for C8 is the minimum suggested value. A 3300µF capacitor or two 2200µF capacitors wired in parallel would be a better choice. T1 transformer can be also a 24 + 24V or 25 + 25V type (i.e. 48V or 50V center tapped). Obviously, the center-tap must be left unconnected. D1 and D2 can be any Schottky barrier diode types. With these devices, the harmonic modifier operation will be hard. Using for D1 and D2 two common 1N4148 silicon diodes, the harmonic modifier operation will be softer.

Part Amplifier:
R1__________________6K8    1W Resistor
R2,R4_____________470R   1/4W Resistors
R3__________________2K   1/2W Trimmer Cermet
R5,R6_______________4K7  1/2W Resistors
R7________________220R   1/2W Resistor
R8__________________2K2  1/2W Resistor
R9_________________50K   1/2W Trimmer Cermet
R10________________68K   1/4W Resistor
R11,R12______________R47   4W Wirewound Resistors
C1,C2,C4,C5________47µF   63V Electrolytic Capacitors
C3________________100µF   25V Electrolytic Capacitor
C6_________________33pF   63V Ceramic Capacitor
C7_______________1000µF   50V Electrolytic Capacitor
C8_______________2200µF   63V Electrolytic Capacitor (See Notes)
D1_________________LED    Any type and color
D2________Diode bridge   200V 6A
Q1,Q2____________BD139    80V 1.5A NPN Transistors
Q3_____________MJ11016   120V 30A NPN Darlington Transistor (See Notes)
Q4_____________MJ11015   120V 30A PNP Darlington Transistor (See Notes)
SW1_______________SPST Mains switch
F1__________________4A Fuse with socket
T1________________220V Primary, 48-50V Secondary 75 to 150VA
                  Mains transformer (See Notes)
PL1_______________Male Mains plug
SPKR______________One or more speakers wired in series or in parallel
                  Total resulting impedance: 8 or 4 Ohm
                  Minimum power handling: 75W

Part Pre Amp:
1,P2______________10K   Linear Potentiometers
P3_________________10K   Log. Potentiometer
R1,R2______________68K   1/4W Resistors
R3________________680K   1/4W Resistor
R4________________220K   1/4W Resistor
R5_________________33K   1/4W Resistor
R6,R16______________2K2  1/4W Resistors
R7__________________5K6  1/4W Resistor
R8,R21____________330R   1/4W Resistors
R9_________________47K   1/4W Resistor
R10_______________470R   1/4W Resistor
R11_________________4K7  1/4W Resistor
R12,R20____________10K   1/4W Resistors
R13_______________100R   1/4W Resistor
R14,R15____________47R   1/4W Resistors
R17,R18,R19_______100K   1/4W Resistors
C1,C4,C5,C6________10µF   63V Electrolytic Capacitors
C2_________________47µF   63V Electrolytic Capacitor
C3_________________47pF   63V Ceramic Capacitor
C7_________________15nF   63V Polyester Capacitor
C8_________________22nF   63V Polyester Capacitor
C9________________470nF   63V Polyester Capacitor
C10,C11,C12________10µF   63V Electrolytic Capacitors
C13_______________220µF   63V Electrolytic Capacitor
D1,D2____________BAT46   100V 150mA Schottky-barrier Diodes (see Notes)
Q1,Q3____________BC546    65V 100mA NPN Transistors
Q2_______________BC556    65V 100mA PNP Transistor
J1,J2___________6.3mm. Mono Jack sockets
SW1,SW2___________SPST Switches