Mini Box 2W Amplifier with Bass Boost Switch

This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc, iPod and CD players, computers and similar devices fitted with line or headphone output. Of course, in most cases you will have to make two boxes to obtain stereo.

Mini-Box 2W Amplifier Circuit Diagram

The circuit was deliberately designed using no ICs and in a rather old-fashioned manner in order to obtain good harmonic distortion behavior and to avoid hard to find components. The amplifier(s) can be conveniently supplied by a 12V wall plug-in adapter. Closing SW1 a bass-boost is provided but, at the same time, volume control must be increased to compensate for power loss at higher frequencies.

In use, R9 should be carefully adjusted to provide minimal audible signal cross-over distortion consistent with minimal measured quiescent current consumption; a good compromise is to set the quiescent current at about 10-15 mA. To measure this current, wire a DC current meter temporarily in series with the collector of Q3.

Parts:

P1_____________10K Log.Potentiometer
R1,R2__________33K 1/4W Resistors
R3_____________33R 1/4W Resistor
R4_____________15K 1/4W Resistor
R5,R6___________1K 1/4W Resistors
R7____________680R 1/4W Resistor
R8____________120R 1/2W Resistor
R9____________100R 1/2W Trimmer Cermet
C1,C2__________10µF 63V Electrolytic Capacitors
C3____________100µF 25V Electrolytic Capacitor
C4,C7_________470µF 25V Electrolytic Capacitors
C5_____________47pF 63V Ceramic Capacitor
C6____________220nF 63V Polyester Capacitor
C8___________1000µF 25V Electrolytic Capacitor
D1___________1N4148 75V 150mA Diode
Q1____________BC560C 45V 100mA PNP Low noise High gain Transistor
Q2____________BC337 45V 800mA NPN Transistor
Q3____________TIP31A 60V 4A NPN Transistor
Q4 ___________TIP32A 60V 4A PNP Transistor
SW1___________SPST switch
SPKR__________3-5 Watt Loudspeaker, 8, 4 or 2 Ohm impedance

• Source
• Red Free Circuits

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10W AUDIO AMPLIFIER WITH BASS BOOST ELECTRONIC DIAGRAM

10W AUDIO AMPLIFIER WITH BASS-BOOST ELECTRONIC DIAGRAM

Adjust the volume control on the minimum and R3 position with a minimum value of resistance as well. try to switch the circuit set in R3 to read the flow of about 20 to 25mA. Wait for 15 minutes, connect the ground of A1, P1, C2, C3dan C4. Connect the output also C9 ground

List Component

• P1 : 22K Log Potemsiometer (Dual gang for stereo)
• C3, 4 : 470uF/25V
• P2 : 100K Log Potemsiometer (Dual gang for stereo)
• C6 : 47pF 63V ceramic ar polyester capasitor
• R2, 4, 8 : 820R 1/4W
• C7 : 10nF 63V polyester capasitor
• R1 : 4K7 1/4W
• C9 : 100nF 63V polyester capasitor
• R3 : 500R 1/2W
• D1 : 1N4148 75V 150mA Diode
• R5 : 82K 1/4W
• IC 1 : NE5532 Low noise Dual Op-amp
• R6, 7 : 47K 1/4W
• Q1 : BC547B 45V 100mA NPN Transitor
• R9 : 10R 1/2W
• Q2 : BC557B 45V 100mA PNP Transitor
• R10 : 0,22 4W(wirewound)
• Q3 : TIP42A 60V 6A PNP Transistor
• C1, 8 : 470nF 63V polyester capasitor
• Q4 : TIP41A 60V 6A NPN Transistor
• C2, 5 : 100uF/25V J1 : RCA audio input socket

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