C1,C4,C8,C9,C10____10?F 63V Electrolytic Capacitors
C2_________________47?F 63V Electrolytic Capacitor
C3_________________47pF 63V Ceramic Capacitor
C5________________220nF 63V Polyester Capacitor
C6________________470nF 63V Polyester Capacitor
C7________________100nF 63V Polyester Capacitor
C11_______________220?F 63V Electrolytic Capacitor

Q1,Q3____________BC546 65V 100mA NPN Transistors
Q2_______________BC556 65V 100mA PNP Transistor

J1,J2___________6.3mm. Mono Jack sockets

SW1_______________SPST Switch

Circuit description:

This design adopts a well established circuit topology for the power amplifier, using a single-rail supply of about 60V and capacitor-coupling for the speaker(s). 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 implement a two-transistors gain-block capable of delivering about 20V RMS output. This provides a very high input overload capability.

Technical data:

Sensitivity:
70mV input for 40W 8 Ohm output

63mV input for 60W 4 Ohm output

Frequency response:
50Hz to 20KHz -0.5dB; -1.5dB @ 40Hz; -3.5dB @ 30Hz

Total harmonic distortion @ 1KHz and 8 Ohm load:
Below 0.1% up to 10W; 0.2% @ 30W

Total harmonic distortion @ 10KHz and 8 Ohm load:
Below 0.15% up to 10W; 0.3% @ 30W

Total harmonic distortion @ 1KHz and 4 Ohm load:
Below 0.18% up to 10W; 0.4% @ 60W
Total harmonic distortion @ 10KHz and 4 Ohm load:
Below 0.3% up to 10W; 0.6% @ 60W
Bass control:
Fully clockwise = +13.7dB @ 100Hz; -23dB @ 10KHz

Center position = -4.5dB @ 100Hz

Fully counterclockwise = -12.5dB @ 100Hz; +0.7dB @ 1KHz and 10KHz
Low-cut switch:
-1.5dB @ 300Hz; -2.5dB @ 200Hz; -4.4dB @ 100Hz; -10dB @ 50Hz

Notes: