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Mini audio amplifier circuit exhibits

2015-01-03 22:20  
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 This article is a mini audio amplifier circuit show. Master the principle is very effective method is to combine text read schematics. The circuit is very simple, very cheap, very effective. The circuit includes a preamplifier, tone controls, DC power supply. 18 watts into 8 ohms - 30 w into a 4 ohm load. Amplifier section hire only three transistors and a few resistors and capacitors in a shunt feedback configuration but can be delivered more than 18 w into 8 ohms and <0.08% @ 1 khz consistent with the onset of clipping (0.04% @ 1 w - 1 khz and 0.02 % @ 1 w - 10 khz) and 30 w into a 4 ohm load. Set to be careful when doing this amplifier, and no acceleration: Connect the power supply unit (before the test, respectively) to the power amplifier, but not pre-amplifier: Input power amplifier must be open. Rotate the mouse R4 entirely to Q1 collector. Position the cursor in the middle of R3 trip. Connect a suitable loudspeaker or 8 ohm 20 w resistor amplifier output. Connect a multimeter, set the measuring approximately 50 v female sexual dysfunction, on the positive and negative ends C5 ground. Switch on the supply and rotate R3 very slowly in order to read about 23 v multimeter display. Cut off the supply, disconnect and reconnect, set the multimeter to measure at least 1 ampere of female sexual dysfunction, in the series the positive supply (may use a second Multimeter in this place will be very welcome). Switch on the supply and rotate R4 very slowly until a reading of about 120 ma display. Again check the voltage at the positive end adjustments, if necessary C5 R3. If it is to adjust R3, R4 will certainly need some adjustments. Wait about 15 minutes, to see if the current is different, adjust if necessary.

Power Amplifier Circuit diagram:

Mini MosFet Power Amplifier

Power Amplifier Parts:

R1_______________2K2 1/4W Resistor
R2______________27K  1/4W Resistor
R3,R4____________2K2 1/2W Trimmers Cermet or Carbon (or 2K)
R5_____________100R  1/4W Resistor
R6_______________1K  1/4W Resistor
R7,R8__________330R  1/4W Resistors

C1______________22μF  25V Electrolytic Capacitor
C2______________47pF  63V Polystyrene or Ceramic Capacitor
C3,C4__________100μF  50V Electrolytic Capacitors
C5____________2200μF  50V Electrolytic Capacitor

Q1____________BC550C  45V 100mA Low noise High gain NPN Transistor
Q2___________IRF530  100V 14A N-Channel Hexfet Transistor (or MTP12N10)
Q3__________IRF9530  100V 12A P-Channel Hexfet Transistor (or MTP12P10)


Preamp Circuit diagram:

Preamp for the Mini-MosFet Amplifier

Preamp Parts:

P1______________50K  Log. Potentiometer (or 47K)
                     (twin concentric-spindle dual gang for stereo)
P2,P3__________100K  Linear Potentiometers
                     (twin concentric-spindle dual gang for stereo)

R1_____________220K  1/4W Resistor
R2_____________100K  1/4W Resistor
R3_______________2K7 1/4W Resistor
R4,R5____________8K2 1/4W Resistors
R6_______________4K7 1/4W Resistor
R7,R8,R13________2K2 1/4W Resistors
R9_______________2M2 1/4W Resistor
R10,R11_________47K  1/4W Resistor
R12_____________33K  1/4W Resistor
R14____________470R  1/4W Resistor
R15_____________10K  1/4W Resistor
R16______________3K3 1/4W Resistor (See Notes)

C1,C2,C9_______470nF  63V Polyester Capacitors
C3,C4___________47nF  63V Polyester Capacitors
C5,C6____________6n8  63V Polyester Capacitors
C7______________10μF  63V Electrolytic Capacitor
C8,C10__________22μF  25V Electrolytic Capacitors
C11____________470μF  25V Electrolytic Capacitor (See Notes)

Q1,Q3_________BC550C  45V 100mA Low noise High gain NPN Transistors
Q2___________2N3819   General-purpose N-Channel FET


Regulated Power Supply Circuit diagram:

Regulated Power  Supply for the Mini-MosFet Amplifier

Regulated Power Supply Parts:

R1_______________3R9 1 or 2W Resistor
R2______________22R  1/4W Resistor
R3_______________6K8 1/4W Resistor
R4_____________220R  1/4W Resistor
R5_______________4K7 1/2W Resistor

C1____________3300μF  50V Electrolytic Capacitor (or 4700μF 50V)
C2,C5__________100nF  63V Polyester Capacitors
C3______________10μF  63V Electrolytic Capacitor
C4_____________220μF  50V Electrolytic Capacitor

D1_____Diode bridge  100V 4A
D2___________1N4002  200V 1A Diode
D3______________LED  Any type and color

IC1___________LM317T 3-Terminal Adjustable Regulator

Q1____________TIP42A  60V 6A PNP Transistor

SW2_____________SPST  Mains switch

T1_____________230V Primary, 35-36V (Center-tapped) Secondary,
                    50-75VA Mains transformer (See Notes)

PL1____________Male Mains plug with cord

A very good and powerful Regulated Power Supply section was implemented by simply adding a PNP power transistor to the excellent  LM317T  adjustable regulator chip. In this way this circuit was able to deliver much more than the power required to drive two Mini-MosFet amplifiers to full output (at least 2Amp @ 40V into 4 Ohm load) without any appreciable effort.Q2 and Q3 in the Power Amplifier must be mounted each on a finned heatsink of at least 80x40x25mm.Q1 and IC1 in the Regulated Power Supply must be mounted on a finned heatsink of at least 45x40x17mm.A power Transformer having a secondary winding rated at 35 – 36V and 50VA (i.e. about 1.4Amp) is required if you intend to use Loudspeaker cabinets of 8 Ohm nominal impedance. To drive 4 Ohm loads at high power levels, a 70 – 75VA Transformer (2Amp at least) will be a better choice. These transformers are usually center tapped: the central lead will be obviously left open.For the stereo version of this project, R16 and C11 in the Preamp will be in common to both channels: therefore, only one item each is necessary. In this case, R16 must be a 1K5 1/2W resistor. The value of C11 will remain unchanged.

Technical data:

Output power:18 Watt RMS into 8 Ohm (1KHz sine wave) – 30 Watt RMS into 4 OhmInput sensitivity of the complete Amplifier:160mV RMS for full outputPower Amplifier Input sensitivity:900mV RMS for full outputPower Amplifier Frequency response @ 1W RMS:flat from 40Hz to 20KHz, -0.7dB @ 30Hz, -1.7dB @ 20HzPower Amplifier Total harmonic distortion @ 1KHz:100mW 0.04% 1W 0.04% 10W 0.06% 18W 0.08%Power Amplifier Total harmonic distortion @10KHz:100mW 0.02% 1W 0.02% 10W 0.05% 18W 0.12%Unconditionally stable on capacitive loadsPreamp Maximum output voltage:4V RMSPreamp Frequency response:flat from 20Hz to 20KHzPreamp Total harmonic distortion @ 1KHz:1V RMS 0.007% 3V RMS 0.035%Preamp Total harmonic distortion @10KHz:1V RMS 0.007% 3V RMS 0.02%Bass control frequency range referred to 1KHz:±20dB @ 40HzTreble control frequency range referred to 1KHz:18dB/-20dB @ 20KHz


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