Amplifier circuit diagram:
Amplifier parts:
R1______________18K 1/4W Resistor R2_______________3K9 1/4W Resistor R3,R6____________1K 1/4W Resistors R4_______________2K2 1/4W Resistor R5______________15K 1/4W Resistor R7______________22K 1/4W Resistor R8_____________330R 1/4W Resistor R9,R10__________10R 1/4W Resistors R11,R12_________47R 1/4W Resistors R13_____________10R 1W Resistor C1_______________1µF 63V Polyester Capacitor C2_____________470pF 63V Polystyrene or Ceramic Capacitor C3______________47µF 25V Electrolytic Capacitor C4______________15pF 63V Polystyrene or Ceramic Capacitor C5_____________220nF 100V Polyester Capacitor C6_____________100nF 63V Polyester Capacitor D1,D2,D3,D4___1N4148 75V 150mA Diodes Q1,Q2________BC560C 45V 100mA Low noise High gain PNP Transistors Q3,Q4________BC556 65V 100mA PNP Transistors Q5___________BC546 65V 100mA NPN Transistor Q6___________BD139 80V 1.5A NPN Transistor Q7___________BD140 80V 1.5A PNP Transistor Q8__________MJ2955 60V 15A PNP Transistor Q9__________2N3055 60V 15A NPN Transistor
Preamplifier circuit diagram:
Preamplifier parts:
P1______________10K Linear Potentiometer P2,P3,P4________47K Linear Potentiometers P5______________10K Log Potentiometer R1,R2___________33K 1/4W Resistors R3_____________220K 1/4W Resistor R4_____________390R 1/4W Resistor R5,R14___________3K9 1/4W Resistors R6,R15___________8K2 1/4W Resistors R7,R16__________12K 1/4W Resistors R8,R11,R17,R20_560R 1/4W Resistors R9,R18___________5K6 1/4W Resistors R10,R19________100R 1/4W Resistors R12______________3K3 1/4W Resistor R13_____________18K 1/4W Resistor C1,C12_________220nF 63V Polyester Capacitors C2,C13_________100pF 63V Ceramic Capacitors C3,C14__________10pF 63V Ceramic Capacitors C4,C15__________47µF 25V Electrolytic Capacitors C5,C16_________100µF 25V Electrolytic Capacitors C6,C7___________10µF 25V Electrolytic Capacitors C8,C11___________4n7 63V Polyester Capacitors C9______________10nF 63V Polyester Capacitor C10_____________47nF 63V Polyester Capacitor Q1___________BC560C 45V 100mA Low noise High gain PNP Transistor Q2,Q3,Q5,Q6__BC546 65V 100mA NPN Transistors Q4___________BC557 45V 100mA PNP Transistor J1,J2__________6.3mm Mono Jack sockets
Power supply circuit diagram:
Power supply parts:
R1_______________3K3 1/2W Resistor C1,C2_________4700µF 50V Electrolytic Capacitors C3,C4__________100nF 63V Polyester Capacitors C5,C6___________47µF 50V Electrolytic Capacitors D1_____________200V 8A Diode bridge D2_____________5mm. Red LED IC2___________78L24 24V 100mA Positive voltage regulator IC IC3___________79L24 24V 100mA Negative voltage regulator IC F1,F2__________3.15A Fuses with sockets T1_____________230V or 115V Primary, 25+25V Secondary 60 to 100VA Mains transformer PL1____________Male Mains plug SW1____________SPST Mains switch
Comments:
The power amplifier stage of this design adopts the still new but already successful 45 Watt Class B Amplifier circuitry appeared on the Audio page of this site one year ago. Please follow the link to read more about this circuit.
Simplicity and ease of construction of this amplifier, combined with the complete absence of manual settings make it ideal for Guitar or Bass amplifier. Enjoy!
The preamplifier features two almost identical three-transistor gain-blocks based on a complementary two-stage circuit with dynamic active load of the output transistor. A circuit topology early used in Revox tape recorders and audio preamplifiers with single rail supplies in the 18 - 24Vdc range.
In this preamp the gain blocks are powered by split supplies of ±24V with two advantages: a high output voltage of about 15V RMS allowing a very wide overload margin and the facility to easily derive the preamp power supply from the power amplifier main supply.
A three-band stacked-type tone control is implemented in the second stage but, unlike the more common passive controls, active controls are used here, allowing better signal to noise ratio and overload margin with no gain loss.
Power supply circuitry is straightforward: a generously rated power transformer with center tapped secondary winding is followed by a diode bridge and two big smoothing electrolytic capacitors. Two small positive and negative voltage regulator ICs provide the ±24V @ 9mA dc supply required by the preamp.
Notes:
- 2N3055 and MJ2955 transistors were listed for Q8 and Q9 in the Amplifier parts as the preferred types, but many different output transistors can be used satisfactorily: TIP3055/TIP2955, TIP35/TIP36, MJ802/MJ4502, MJ15003/MJ15004 amongst others.
- Discrete op-amp output transistors Q6 and Q7 do not require any heatsink as their cases remain at ambient temperature. Power transistors Q8 and Q9 should be mounted on a black, finned heatsink as usual.
Power Amplifier Technical data:
- Output power (1KHz sinewave):
- 45 Watt RMS into 8 Ohms - 69W RMS into 4 Ohms
- Sensitivity:
- 0.81V RMS input for 45W output
- Frequency response @ 1W RMS:
- 15Hz to 23KHz -0.2dB
- Total harmonic distortion @ 1KHz:
- 1W 0.008% 20W 0.008% 45W 0.016%
- Total harmonic distortion @10KHz:
- 1W 0.01% 20W 0.015% 45W 0.025%
- Unconditionally stable on capacitive loads
Preamplifier Technical data:
- Maximum output voltage (1KHz sinewave):
- 14.8V RMS
- Sensitivity:
- 127mV RMS input for 14.8V RMS output
- 8.5mV RMS input for 1V RMS output
- Total harmonic distortion @ 1KHz:
- 1V RMS output <0.001% 5V RMS output <0.05%
- Total harmonic distortion @10KHz:
- 1V RMS output <0.001% 5V RMS output <0.035%
