Tuesday, December 15, 2009
PIC LCF METER
This simple PIC-based unit was designed to measure and display the values of inductors and capacitors.
As a by-product of the technique used, it can also display the frequency of an external 0V / +5V signal source.
Capacitance: 1pF to 6500mFInductance : 1mH to 10H
Frequency : 0,05Hz to 5MHz
Saturday, December 12, 2009
32W HI-FI AUDIO POWER AMPLIFIER - TDA2050
The TDA 2050 is a monolithic integrated circuit in Pentawatt package, intended for use as an audio class AB audio amplifier. Thanks to its high power capability the TDA2050 is able to provide up to 35W true rms power into 4 ohm load @ THD = 10%, VS = ±18V, f = 1KHz and up to 32W into 8ohm load@ THD = 10%, VS = ±22V, f = 1KHz.
Moreover, the TDA 2050 delivers typically 50W music power into 4 ohm load over 1 sec at VS= 22.5V, f = 1KHz.The high power and very low harmonic and crossover distortion (THD = 0.05% typ, @ VS = ±22V, PO = 0.1 to 15W, RL=8ohm, f = 100Hz to 15KHz) make the device most suitable for both HiFi and high class TV sets.
- HIGH OUTPUT POWER
- (50W MUSIC POWER IEC 268.3 RULES)
- HIGH OPERATING SUPPLY VOLTAGE (50V)
- SINGLE OR SPLIT SUPPLY OPERATIONS
- VERY LOW DISTORTION
- SHORT CIRCUIT PROTECTION (OUT TO GND)
- THERMAL SHUTDOWN
R1----22K
R2----680
R3----22K
R4----2.2
C1----1mf
C2----22mf
C3----100nf
C4----100nf
C5----220mf
C6----220mf
C7----0.47mf
IC----TDA2050
Tuesday, December 8, 2009
120W MOSFET Power Amplifier with LM4702 Driver Chip.
National Semiconductor has been fast at work designing analog products for the high-end audiophile market. As fortune would have it, these products such as the LM4780 Power Amplifier Chip and the LM4702 Driver Chip are easy to implement into high-quality designs for the audio DIYer.
National recently introduced the LM4702, a high-voltage driver chip that interfaces bipolar or MOSFET output devices. The LM4702 provides two small signal, input stages and voltage amplification stages (VAS). All you need to do is design a suitable bias system and output stage.
Not to be outdone in making the job easy for us amateurs, National provides a comprehensive design outline, guide to printed circuit board construction, ideas for the power supply, bill of materials, and suggested layout. In an application note dated May 20061, the company described an amplifier using high-quality construction techniques and off-the-shelf passive components. The result is an amplifier with a vanishingly low level of distortion, 0.0006%. See More...
Thursday, November 26, 2009
AUDIO POWER METER WITH LM3915
This VU (volume-unit) meter is capable of monitoring anddisplaying power levels present at the speaker terminals ofan stereo audio power amplifier.
The levels are displayed in ten discrete steps. This meter is not designed to give an
accurate display of the power levels.It is designed to give an approximate visual indication of the audio power output of each channel. For many situations - disco, parties - this is all which is required: the flashing LED's add atmosphere to the situation.
accurate display of the power levels.It is designed to give an approximate visual indication of the audio power output of each channel. For many situations - disco, parties - this is all which is required: the flashing LED's add atmosphere to the situation.
LM3915. This is a monolithic Dot/Bar Display Driver IC made by National Semiconductor. It takes an analog voltage input on pin 5 then drives 10 LED's providing a logarithmic 3dB/step analog display. When measuring power, a 3dB increase means that the power input has doubled. As the power doubles, an additional LED will be lit until the maximum is reached. The display can be bar or moving dot depending on the connection of pin 9 to the positive supply. The LED drive current is regulated which eliminates the need for current limiting resistors.
The supply voltage can be between 3V to 25V. You can download the data sheet from the National Semiconductor website at: http://www.national.com/
The IC is suited to signals with a wide dynamic range such as audio, power, light intensity. In many applications a bargraph meter is faster, more rugged and has higher visibility than an analog (moving coil) or LCD meter.
The IC is suited to signals with a wide dynamic range such as audio, power, light intensity. In many applications a bargraph meter is faster, more rugged and has higher visibility than an analog (moving coil) or LCD meter.
PARTS LIST
R1-----10K
R2------1K
R3-----390
R4-----2,7K
P1-----100K TRIMMER POT.
C1-----10mf 25v
D1..D10---LED red
Thursday, November 12, 2009
Build a Tube Preamp for guitar with tone control
I decided recently to build a tube preamp for my home studio. Please note, however, that this is not a circuit for the novice electronics builder. The circuit itself is simple, but unlike most semiconductor projects, this one uses voltages near 300V. The danger of electrocution is present and neither the author can assume responsibility for protecting you.
If you are not familiar with good construction and safety practices for high – voltage electronics, do not attempt to build this circuit.
So how does it sound?
This preamp won’t make the sound of an overdriven Marshall stack, nor is it a heavy metal distortion unit, but it does produce tonal colors ranging from a slight “warming” to soft distortion. Turning down the drive control produces a somewhat brighter sound with no distortion? Turning the drive all the way up produces distortion that really bites on the bass strings and softens out on the higher notes. Driving the unit hard also produces a bit of a compression effect. With my two – finger power chord playing style, I find the overall effect quite pleasing.
If you are not familiar with good construction and safety practices for high – voltage electronics, do not attempt to build this circuit.
So how does it sound?
This preamp won’t make the sound of an overdriven Marshall stack, nor is it a heavy metal distortion unit, but it does produce tonal colors ranging from a slight “warming” to soft distortion. Turning down the drive control produces a somewhat brighter sound with no distortion? Turning the drive all the way up produces distortion that really bites on the bass strings and softens out on the higher notes. Driving the unit hard also produces a bit of a compression effect. With my two – finger power chord playing style, I find the overall effect quite pleasing.
Circuit description
The preamp circuit, based on a design in the 1975 RCA Receiving Tube Manual, uses a 12AX7 tube as a two stage, voltage gain amplifier.
This “generic” circuit is similar to what you will find in most guitar amp rpeamps.
The 12AX7 (6N2P and ECC83 are equivalent tubes) is probably the most common tube used in the music business. Almost all current tube effects use this tube, as do most vintage tube amps.
The 12AX7 was designed for use in audio applications requiring exceptionally low hum and noise levels. It is a high gain, twin triode device, having tow identical sections sharing a common heater filament.
The guitar or other input feeds J1 and goes to the grid of the first tube stage, which produces a voltage gain of about 30.
This boosts the guitar’s 40 mV (nominal) input up to about up to about 1.2V.
Coupling capacitor C2 picks off the amplified signal while blocking the high voltage plate supply. The signal then goes through the tone control circuit (R5-R9 and C3-C6) before feeding the second stage’s input. Potentiometer R10 is a voltage divider that sets the drive.
The second tube stage provides a gain of ten. The output signal couples through blocking capacitor C8 to the load resistance (R13 and R14). Control R14 varies the output signal level at J2, up to a maximum of about 1.5V. this should feed a relatively high impedance stage; 600ohm mixer inputs are not recommended. Resistors R4 and R12 are bias resistors that allow the tube cathodes to develop a positive potential with respect to ground. Capacitors C1 and C7 filter any ripple appearing across these resistors.
POWER SUPPLY.
Transformer is a dual secondary type rated at 250VAC center-tapped for the tube’s plate supply and 6.3VAC for the tube filament.
The output from a full-wave rectifier is 0.7 times the input AC voltage, so about 185V appears across C10 and under load, about 140V appears across.
Any transformer that produces 150 to 275VAC should work fine.
You can also use a transformer with a 12VAC filament winding by grounding ground pin 9 of the 12AX7 and running the 12VAC into pins 4 and 5.
PARTS LIST
R1, R5, R13------------47K 1/2W
R2----------------------1M 1/2W
R3, R8----------------100K 1/2W
R4---------------------2.2K 1/2W
R6, R9, R10-------------1M potentiometer
R7---------------------10K 1/2W
R11--------------------68K 1/2W
R12--------------------15K 1/2W
R14--------------------50K potentiometer
R15--------------------47K 1W
R16------------------220K 1/2W
C1, C7------------------25mf 62V
C2, C8-----------------220nf 400V ceramic disk
C3----------------------20nf 400V ceramic disk
C4, C6------------------1.2nf 400V ceramic disk
C5---------------------220pf 400V ceramic disk
C9, C10-------------33-47mf 400V electrolytic
D1 – D4------------------1N4004
F1-----------------------0.1A fuse
J1, J2--------------------phone jack
T------------------------2x250V 50ma + 6V 1 A transformer
V1-----------------------12AX7 or ECC83, 6N2P
S1---------------------- -switch
Misc---------------------9-pin tube socket
Saturday, November 7, 2009
600 WATT HI-FI Power Amplifiers PA600
Towards the end of 1995, a scaled-down version of this circuit appeared in ’Elektor’ as ’PA 300’.
It is virtually the same circuit except for a less powerful output stage (now two complementary
pairs instead of five with additional driver stage) and minor changes in component selection and values. However, as ’Elektor’ is much more popular, many people built a ’PA 300’ without knowing it was scaled down from a bigger amplifier.
MORE.... click Here
OTHER.... click Here
Wednesday, November 4, 2009
ONE CHIP FM RADIO ( KA22429 )
The KA22429 is a monolithic integrated circuit designed for Portable FM radio.It is consistng of RF input stage, Mixer, IF, Mute control and Loop (earphone drive) AMP.
It is suitable a pocket - size radio.
FEATURES
- Minimum number of external parts required
- It is able to a single trimmer tuning
- No FM det coil
- It is FLL detect system (76KHz)
- Operating voltage: Vcc= 1.8V~6.0V
Thursday, October 22, 2009
STEREO FM TRANSMITTER WITH I.C. BH1417
This is the latest BH1417 Stereo Encoder design from RHOM that includes a lot of great features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference and crystal based stereo encoder for stereo transmission.
BH1417 can be supplied with 6 - 15V voltage, consumes only around 25mA while providing very sound quality and improved 40dB channel separation. BH1417 is only available in SOP22 IC case and this may be an inconvenience for some folks.
On the other hand, because the chip is smaller than regular DIP-based ICs it is possible to fit the entire stereo coder on a small PCB.
BH1417 requires 7.6MHz crystal oscillator which is pretty hard to find. The good news is that you can use 7.68 MHz crystal instead. In fact our BH1417 stereo encoder prototype uses 7.68 MHz crystal.
This has absolutely no effect on stereo encoding process, we have tested it and stereo sound is crystal clear.
Specifications:
Supply Voltage: 9 - 16V
Transmission Frequency: 87.7 - 88.9MHz, 106.7 - 107.9MHz (200kHz steps)
Output RF Power: 20mW
Audio Frequency: 20 - 15KHz
Separation: 40dB
Power Consumption: 30mA
Frequency Selection / Calibration
Frequency selection is very straight forward. Simply select transmission frequency at which you would like to transmit, set the combination for 4-DIP switch and BH1417 will immediately tune to that frequency. If you can't hear the transmitted audio signal on your FM receiver then re-adjust 2.5 turn variable coil until you can hear the signal. If you have a laboratory power supply you may try to vary the voltage supply from 9 to 16V. While doing that BH1417 will automatically vary the voltage for MV2109 or ZMV833ATA varicap diode making sure that there's no frequency drift.
Saturday, October 3, 2009
Thursday, October 1, 2009
Sunday, September 27, 2009
100 W 8 ohms MOSFET amplifier with IRF9540 - IRF540
The Schematic Diagram is a basic MOSFET amplifier. Output power is 100 Wrms under 8 ohms or 160 Wrms under 4 ohms with distortion is 0.001 %. Bandwidth at -3 db is from 4 Hz to 100 Khz .
Input sensitivity is 1.2 volts. The gain of 27DB is archived by R7/R6. It may be modified by changing R7 value. Transistors T5 and T6 makes the second differential stage. Transistors T3 and T4 works as a current mirror source. They push the second differential stage to drain equal current. Doing so we get a high gain and an excellent linearity. Output MOSFET transistors works in AB class, their quiescent current is set at 100 mA trough P1. For setting quiescient current, you must set P1 in minimal resistance, place a multimeter in mV DC range on R14 or R15 leads, turn slowly the screw until you read a 33 mV value, which correspond to a 100 mA quiescent current.
F1 and F2 works as an elementary output short-circuit protection. The power supply must have a value between 45 and 55 Volts DC (positive and negative). One heatsink with a thermal resistance less of 2° C / W is required.
All resistors are 1% metal film 1/4 watt. Before connecting a speaker to the amplifier output, connect a multimeter to the output and look on DC output voltage. This level must not be greater than 50 mV. If it is so, check all amplifier for error. Also, change T2 with another device and check again. This amplifier is very simple to build and low cost.
Part List
C1 = 2,2 µF-100 VC2 = 330 pF-100 V
C3 = 100 nF -100 V
C4 = 100 µF 63 V
C5, C6 = 18 pF
C7 = 100 nF
R1, R3 = 47 K
R2 = 2K2
R4, R5 = 3K9
R6 = 1 K
R7 = 27 K
R8, R9, R11 = 100 ohms
R10 = 10 K
R12, R13 = 470 ohms
R14, R15 = 0.33 ohms 5 watts
R16 = 10 ohms 3 watts
T1, T2 = 2N5401, ZTX558, BC556B
T3, T4 = BF470, MJE350, 2SB649
T5, T6 = BF469, MJE340, 2SD669
T7 = IRF540, IRFP240, 2SK1530, 2SJ162, BUZ900DP, BUZ901DP
T8 = IRF9540, IRFP9240, 2SJ201, 2SK1058, BUZ905DP,
P1 = 2K5 trimmer
F1, F2 = 3 A
power supply
One 2x40 volts 225 VA transformer is exactly what we need for one mono amplifier. For a stereo amplifier, one 2x40 volts 500 VA transformer is required.
Use at least 4x6800 µF 63-80 V reservoir capacitors. The more caps you use, the better the ripple rejection.
4K7 5W resistors are used to discharge reservoir capacitors once mains is set off.
Thursday, September 24, 2009
VU Meter with UAA180
The circuit was designed based on the operation of Siemens UAA180 as it functions as a LED driver for light band displays for measuring the level of audio signals.
Part List
R1----22K--1/4W
R2----27K--1/4W
R3----33K--1/4W
C1----1nF
D13---1N4148
P1-----10K--TRIMMER
IC1----UAA180
D1...12-LEDS
Sunday, September 20, 2009
Thursday, September 17, 2009
Stereo Digital Volume Control with DS1802
PIN DESCRIPTION
L0, L1 - Low End of Resistor
H0, H1 - High End of Resistor
W1,W2 - Wiper End of Resistor
VCC - 3V/5V Power Supply Input
RST - Serial Port Reset Input
D - Serial Port Data Input
CLK - Serial Port Clock Input
MODE - Mode Select Input
UC0, UC1 - Up Control Pushbutton Inputs
DC0, DC1 - Down Control Pushbutton
Inputs
VU, VD - Volume-Up/Volume-Down
Inputs
B0, B1 - Balance Pot-0, Pot-1 Inputs
GND - Digital Ground
MUTE - Mute
AGND - Analog Ground
ZCEN - Zero-Crossing Detect Input
COUT - Cascade Output
FEATURES
- Ultra-low power consumption
- Operates from 3V or 5V supplies
- Two digitally controlled, 65-position potentiometers including mute
- Logarithmic resistive characteristics (1 dB per step)
- Zero-crossing detection eliminates noise caused by wiper movement
- Digital or mechanical pushbutton wiper control
- Serial port provides means for setting and reading both potentiometers wipers
- 20-pin SOIC and 20-pin TSSOP for surface mount applications
- Operating Temperature Range: -40°C to +85°C
- Software and hardware mute
- Resistance Available: 45 kW
Monday, September 7, 2009
Thursday, September 3, 2009
LM-3875 Amplifier with ECC88 Tube Buffer
TECHNICAL SPECIFICATIONS
Power Supply
- toroidal transformer 230V/8*12V/180VA
- output amplifier rails 2*32V DC(2*24V), two bridges with two BYW95C diodes in parallel
- caps Samsung 470uF/100V, four per channel
- tube buffer rails 2*45V (half-wave voltage doubler of 1*36Vac), two BYW95C's, CLC network, 470uF Samsung +100mH+6800uF Panasonic
- tube heating 6V DC, 4xBYW26c, 2* 1000uF Nichicon, stabilized with 7806, 1*1000uF Nichicon .
Input
-standard gold plated cinches, Alps selector 2*1in3, Preh pot 2*10klog .
Tube Buffer
- tube E88CC (NOS Tesla CH), or ECC88 (OS Siemens)
- standard metal-film resistors .
Output Amplifier
- LM 3875 - inverted setup - gain ca 30dB
- input capacitor 2u2/250V ROE MKT, LPF 2*680pF ROE MKC, 2*47nF/160V ROE MKP
- standard metal-film resistors
- output DC offset about -5mV .
Power on Delay
- relay 10A/30VDC on output .
Input Impedance
10k .
Frequency Range
10Hz-20kHz (-1dB, -2dB)/1W/8ohm/THD=0,1%/IMD2=0.075% .
Output Power
36Vpp - 20W RMS (8ohm/both amps on/THD lower than 0.15% 100Hz-20kHz)
24Vpp - 18W RMS (4ohm/both amps on/THD lower than 0.25% 100Hz-20kHz) .
MORE...... http://www.moxtone.com/Tube-buffered%20Gainclone.htm
Tuesday, August 11, 2009
LM1894 Dynamic Noise Reduction System DNR
INTRODUCTION
The operating principles of a single-ended or non-complementary audio noise reduction system, DNR, have been covered extensively in a previous application note AN384, Audio Noise Reduction and Masking. Although the system was originally implemented with transconductance amplifiers (LM13600) and audio op-amps (LM387), dedicated I/Cs have since been developed to perform the DNR function.
The LM1894 is designed to accommodate and noise reduce the line level signals encountered in video recorders, audio tape recorders, radio and television broadcast receivers, and automobile radio/cassette receivers. A companion device, the LM832, is designed to handle the lower signal levels available in low voltage portable audio equipment. This note deals chiefly with the practical aspects of using the LM1894, but the information given can also be applied to the LM832.
THE BASIC DNR APPLICATION CIRCUIT
At the time of writing, the LM1894 has already found use in a large variety of applications. These include:
AUTOMOTIVE RADIOS
TELEVISION RECEIVERS
HOME MUSIC CENTERS
PORTABLE STEREOS (BOOM BOXES)
SATELLITE RECEIVERS
AUDIO CASSETTE PLAYERS
AVIONIC ENTERTAINMENT SYSTEMS
HI-FI AUDIO ACCESSORIES
BACKGROUND MUSIC SYSTEMS
ETC.
The operating principles of a single-ended or non-complementary audio noise reduction system, DNR, have been covered extensively in a previous application note AN384, Audio Noise Reduction and Masking. Although the system was originally implemented with transconductance amplifiers (LM13600) and audio op-amps (LM387), dedicated I/Cs have since been developed to perform the DNR function.
The LM1894 is designed to accommodate and noise reduce the line level signals encountered in video recorders, audio tape recorders, radio and television broadcast receivers, and automobile radio/cassette receivers. A companion device, the LM832, is designed to handle the lower signal levels available in low voltage portable audio equipment. This note deals chiefly with the practical aspects of using the LM1894, but the information given can also be applied to the LM832.
THE BASIC DNR APPLICATION CIRCUIT
At the time of writing, the LM1894 has already found use in a large variety of applications. These include:
AUTOMOTIVE RADIOS
TELEVISION RECEIVERS
HOME MUSIC CENTERS
PORTABLE STEREOS (BOOM BOXES)
SATELLITE RECEIVERS
AUDIO CASSETTE PLAYERS
AVIONIC ENTERTAINMENT SYSTEMS
HI-FI AUDIO ACCESSORIES
BACKGROUND MUSIC SYSTEMS
ETC.
MORE......http://www.national.com/ds/LM/LM1894.pdf
Thursday, August 6, 2009
Monday, August 3, 2009
Sunday, July 19, 2009
12 Volt Lamp Dimmer
Here is a 12 volt / 2 amp lamp dimmer that can be used to dim a standard 25 watt automobile brake or backup bulb by controlling the duty cycle of a as table 555 timer oscillator. When the wiper of the potentiometer is at the uppermost position, the capacitor will charge quickly through both 1K resistors and the diode, producing a short positive interval and long negative interval which dims the lamp to near darkness. When the potentiometer wiper is at the lowermost position, the capacitor will charge through both 1K resistors and the 50K potentiometer and discharge through the lower 1K resistor, producing a long positive interval and short negative interval which brightens the lamp to near full intensity. The duty cycle of the 200 Hz square wave can be varied from approximately 5% to 95%. The two circuits below illustrate connecting the lamp to either the positive or negative side of the supply.
10 - 20Watt Guitar Amplifier
Parts:
P1______________4K7 Linear Potentiometer
P2_____________10K Log. Potentiometer
R1,R2__________68K 1/4W Resistors
R3____________220K 1/4W Resistor
R4,R6,R11_______4K7 1/4W Resistors
R5_____________27K 1/4W Resistor
R7______________1K 1/4W Resistor
R8______________3K3 1/2W Resistor
R9______________2K 1/2W Trimmer Cermet
R10___________470R 1/4W Resistor
R12_____________1K5 1/4W Resistor
R13___________470K 1/4W Resistor
R14____________33K 1/4W Resistor
C1____________100pF 63V Ceramic Capacitor
C2____________100nF 63V Polyester Capacitor
C3____________470μF 35V Electrolytic Capacitor
C4____________220nF 63V Polyester Capacitor (Optional, see Notes)
C5_____________47μF 25V Electrolytic Capacitor (Optional, see Notes)
C6______________1μF 63V Polyester Capacitor
C7,C8,C9,C10___47μF 25V Electrolytic Capacitors
C11____________47pF 63V Ceramic Capacitor
C12__________1000μF 35V Electrolytic Capacitor
C13__________2200μF 35V Electrolytic Capacitor
D1_____________5mm. Red LED
D2,D3________1N4004 400V 1A Diodes
Q1,Q2_________2N3819 General-purpose N-Channel FETs
Q3____________BC182 50V 200mA NPN Transistor
Q4____________BD135 45V 1.5A NPN Transistor (See Notes)
Q5____________BDX53A 60V 8A NPN Darlington Transistor
Q6____________BDX54A 60V 8A PNP Darlington Transistor
J1,J2________6.3mm. Mono Jack sockets
SW1____________1 pole 3 ways rotary switch (Optional, see Notes)
SW2____________SPST Mains switch
F1_____________1.6A Fuse with socket
T1_____________220V Primary, 48V Center-tapped Secondary 20 to 30VA Mains transformer
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: 20W
Circuit description:
The aim of this design is to reproduce a Combo amplifier of the type very common in the 'sixties and the 'seventies of the past century. It is well suited as a guitar amplifier but it will do a good job with any kind of electronic musical instrument or microphone.
5W power output was a common feature of these widespread devices due to the general adoption of a class A single-tube output stage (see the Vox AC-4 model).
Furthermore, nowadays we can do without the old-fashioned Vib-Trem feature frequently included in those designs.
The present circuit can deliver 10W of output power when driving an 8 Ohm load, or about 18W @ 4 Ohm.
It also features a two-FET preamplifier, two inputs with different sensitivity, a treble-cut control and an optional switch allowing overdrive or powerful treble-enhancement.
Technical data are quite impressive for so simple a design:
Sensitivity: 30mV input for 10W output
Frequency response: 40 to 20KHz -1dB
Total harmonic distortion @ 1KHz and 10KHz, 8 Ohm load: below 0.05% @ 1W, 0.08% @ 3.5W, 0.15% at the onset of clipping (about 10W).
Notes:
SW1 and related capacitors C4 & C5 are optional.
When SW1 slider is connected to C5 the overdrive feature is enabled.
When SW1 slider is connected to C4 the treble-enhancer is enabled.
C4 value can be varied from 100nF to 470nF to suit your treble-enhancement needs.
In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q4) should be in as close thermal contact with the output transistors as possible. Therefore a TO126-case transistor type was chosen for easy bolting on the heatsink, very close to the output pair.
To set quiescent current, remove temporarily the Fuse F1 and insert the probes of an Avo-meter in the two leads of the fuse holder.
Set the volume control to the minimum and Trimmer R9 to its minimum resistance.
Power-on the circuit and adjust R9 to read a current drawing of about 25 to 30mA.
Wait about 15 minutes, watch if the current is varying and readjust if necessary.
P1______________4K7 Linear Potentiometer
P2_____________10K Log. Potentiometer
R1,R2__________68K 1/4W Resistors
R3____________220K 1/4W Resistor
R4,R6,R11_______4K7 1/4W Resistors
R5_____________27K 1/4W Resistor
R7______________1K 1/4W Resistor
R8______________3K3 1/2W Resistor
R9______________2K 1/2W Trimmer Cermet
R10___________470R 1/4W Resistor
R12_____________1K5 1/4W Resistor
R13___________470K 1/4W Resistor
R14____________33K 1/4W Resistor
C1____________100pF 63V Ceramic Capacitor
C2____________100nF 63V Polyester Capacitor
C3____________470μF 35V Electrolytic Capacitor
C4____________220nF 63V Polyester Capacitor (Optional, see Notes)
C5_____________47μF 25V Electrolytic Capacitor (Optional, see Notes)
C6______________1μF 63V Polyester Capacitor
C7,C8,C9,C10___47μF 25V Electrolytic Capacitors
C11____________47pF 63V Ceramic Capacitor
C12__________1000μF 35V Electrolytic Capacitor
C13__________2200μF 35V Electrolytic Capacitor
D1_____________5mm. Red LED
D2,D3________1N4004 400V 1A Diodes
Q1,Q2_________2N3819 General-purpose N-Channel FETs
Q3____________BC182 50V 200mA NPN Transistor
Q4____________BD135 45V 1.5A NPN Transistor (See Notes)
Q5____________BDX53A 60V 8A NPN Darlington Transistor
Q6____________BDX54A 60V 8A PNP Darlington Transistor
J1,J2________6.3mm. Mono Jack sockets
SW1____________1 pole 3 ways rotary switch (Optional, see Notes)
SW2____________SPST Mains switch
F1_____________1.6A Fuse with socket
T1_____________220V Primary, 48V Center-tapped Secondary 20 to 30VA Mains transformer
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: 20W
Circuit description:
The aim of this design is to reproduce a Combo amplifier of the type very common in the 'sixties and the 'seventies of the past century. It is well suited as a guitar amplifier but it will do a good job with any kind of electronic musical instrument or microphone.
5W power output was a common feature of these widespread devices due to the general adoption of a class A single-tube output stage (see the Vox AC-4 model).
Furthermore, nowadays we can do without the old-fashioned Vib-Trem feature frequently included in those designs.
The present circuit can deliver 10W of output power when driving an 8 Ohm load, or about 18W @ 4 Ohm.
It also features a two-FET preamplifier, two inputs with different sensitivity, a treble-cut control and an optional switch allowing overdrive or powerful treble-enhancement.
Technical data are quite impressive for so simple a design:
Sensitivity: 30mV input for 10W output
Frequency response: 40 to 20KHz -1dB
Total harmonic distortion @ 1KHz and 10KHz, 8 Ohm load: below 0.05% @ 1W, 0.08% @ 3.5W, 0.15% at the onset of clipping (about 10W).
Notes:
SW1 and related capacitors C4 & C5 are optional.
When SW1 slider is connected to C5 the overdrive feature is enabled.
When SW1 slider is connected to C4 the treble-enhancer is enabled.
C4 value can be varied from 100nF to 470nF to suit your treble-enhancement needs.
In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q4) should be in as close thermal contact with the output transistors as possible. Therefore a TO126-case transistor type was chosen for easy bolting on the heatsink, very close to the output pair.
To set quiescent current, remove temporarily the Fuse F1 and insert the probes of an Avo-meter in the two leads of the fuse holder.
Set the volume control to the minimum and Trimmer R9 to its minimum resistance.
Power-on the circuit and adjust R9 to read a current drawing of about 25 to 30mA.
Wait about 15 minutes, watch if the current is varying and readjust if necessary.
http://www.electronics-lab.com/projects/audio/030/index.html
Wednesday, July 8, 2009
AUDIO MICROPHONE PREAMPLIFIER - Single IC
This circuit will is useful if you have a microphone or a device that produces a low audio level and you want to connect it to a stereo or something. This circuit will boost it's output level.
Parts List:
Component:---Value:--------------Datasheet:--------Qty:
Resistor----------10 K----------------- Not Available-------03
Resistor-----------1 K------------------Not Available-------01
Resistor------ --100K to 1M Pot------- Not Available-------01
Capacitor--------0.1 uF-----------------Not Available-------01
Capacitor--------4.7 uF-----------------Not Available-------01
IC--------------LM358-------------------Available--------- 01
Microphone----Electret-----------------Not Available-------01
[read here...]
Parts List:
Component:---Value:--------------Datasheet:--------Qty:
Resistor----------10 K----------------- Not Available-------03
Resistor-----------1 K------------------Not Available-------01
Resistor------ --100K to 1M Pot------- Not Available-------01
Capacitor--------0.1 uF-----------------Not Available-------01
Capacitor--------4.7 uF-----------------Not Available-------01
IC--------------LM358-------------------Available--------- 01
Microphone----Electret-----------------Not Available-------01
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