Audio Preamplifier with Tone Control

The Audio Preamplifier Circuit sensitivity and overload margin were designed to cope with most modern music programme sources like CD players, Tape recorders, iPods, Computer audio outputs, Tuners etc. The source selecting switches and input connectors are not shown and their number and arrangement are left to the constructor's choice.

To obtain a very high input overload margin of the audio preamplifier, the volume control was placed at the preamplifier input. After a unity gain, impedance converter stage (Q1) a negative-feedback Baxandall-type Bass and Treble tone control stage was added. As this stage must provide some gain (about 5.6 times) a very low noise, "bootstrapped" two-transistors circuitry with FET-input was implemented. This stage features also excellent THD figures up to 4V RMS output and a low output impedance, necessary to drive properly the Mini-MosFet Power Amplifier, but can also be used for other purposes.

Audio Preamplifer Parts List:

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

Read more ...

Mosfet Audio Power Amplifier 18W

This audio project is designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality.

This audio amplifier circuit employs only three transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm with <0.08% THD @ 1KHz at the onset of clipping (0.04% @ 1W - 1KHz and 0.02% @ 1W - 10KHz) and up to 30W into a 4 Ohm load.

To obtain such a performance and to ensure overall stability of this very simple circuitry, a suitable regulated dc power supply is mandatory. This is not a snag because it also helps in keeping noise and hum of the preamp to very low levels and guarantees a predictable output power into different load impedances. Finally, as the audio amplifier requires only a single rail supply, a very good dc voltage regulator capable of supplying more than 2 Amps @ 40V can be implemented with a few parts also.


Audio 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)

Audio Amplifier with mosfet

Read more ...

Headphone Amplifier

This circuit is a high quality headphone amplifier. It's no need for a preamplifier. This circuit equipped with a symetrical power supply.

Amplifier parts list:

P1 - 22K Log.Potentiometer (Dual-gang for stereo)
R1 - 560R 1/4W Resistor
R2,R3 - 10K 1/4W Resistors
R4 - 12K 1/4W Resistor
R5,R6 - 2R2 1/4W Resistor
R7 - 22R 1/2W Resistor
C1 - 1µF 63V Polyester Capacitor
C2,C3,C4 - 100µF 25V Electrolytic Capacitors
C5 - 22pF 63V Polystyrene or Ceramic Capacitor
C6 - 22µF 25V Electrolytic Capacitor
IC1 - LM833 or NE5532 Low noise Dual Op-amp
Q1,Q3 - BC337 45V 800mA NPN Transistors
Q2,Q4 - BC327 45V 800mA PNP Transistors
J1 - RCA audio input socket

Power supply parts List:

R8 - 2K2 1/4W Resistor
C7,C8 - 2200µF 25V Electrolytic Capacitors
D1 - 100V 1A Diode bridge
D2 - 5mm. or 3mm. Red LED
IC2 - 7815 15V 1A Positive voltage regulator IC
IC3 - 7915 15V 1A Negative voltage regulator IC
T1 - 220V Primary, 15 + 15V Secondary 5VA Mains transformer
PL1 - Male Mains plug
SW1 - SPST Mains switch

Notes:

• Can be directly connected to CD players, tuners and tape recorders.
• Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohm.
• Old 8 Ohm impedance headphones can be also driven, but these obsolete devices are not recommended.
• Schematic shows left channel and power supply (common to both channels).
• Numbers in parentheses show IC1 right channel pin connections.
• A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 & C4. Then connect separately the input and output grounds to the power supply ground.
  

Source

Read more ...

Precision Audio Millivoltmeter

This electronic circuit is audio milivolt meter. It measures 10mV to 50Volt RMS in eight ranges. Simply connect to your Avo-meter set to 50µA range

Parts:

R1 - 909K 1/2W 1% Metal Oxide Resistor
R2 - 90K9 1/2W 1% Metal Oxide Resistor
R3 - 9K09 1/2W 1% Metal Oxide Resistor
R4 - 1K01 1/2W 1% Metal Oxide Resistor
R5 - 100K 1/4W Resistor
R6 - 2M2 1/4W Resistor
R7 - 82K 1/4W Resistor
R8 - 12K 1/4W Resistor
R9 - 1K2 1/4W Resistor
R10 - 3K3 1/4W Resistor
R11 - 200R 1/2W Trimmer Cermet
C1 - 330nF 63V Polyester Capacitor
C2,C3 - 100µF 25V Electrolytic Capacitor
C4 - 220µF 25V Electrolytic Capacitor
C5 - 33pF 63V Polystyrene Capacitor
C6 - 2µ2 63V Electrolytic Capacitor
D1-D4 - 1N4148 75V 150mA Diodes
IC1 - CA3140 Op-amp
IC2 - CA3130 Op-amp
SW1 - 2 Holes 5 ways rotary switch
SW2 - SPDT switch
J1 - RCA audio input socket
J2,J3 - 4mm. output sockets
B1 - 9V PP3 Battery
Clip for PP3 Battery


Notes:

• Connect J2 and J3 to an Avo-meter set to 50µA range:
• Switching SW2 the four input ranges will be multiplied by 5
• Total fsd ranges are: 10mV, 50mV, 100mV, 500mV, 1V, 5V, 10V, 50V
• Set R11 to read 1V in the 1V range, with a sine wave input of 1V @ 1KHz
• Compare the reading with that of another known precision Millivoltmeter or with an oscilloscope.
• The oscilloscope reading must be a sinewave of 2.828V peak to peak amplitude
• Frequency response is flat in the 20Hz-20KHz range
• If you have difficulties in finding resistor values for R1, R2, R3 & R4, you can use the following trick:

R1 = 10M + 1M in parallel
R2 = 1M + 100K in parallel
R3 = 100K + 10K in parallel
R4 = 1K2 + 6K8 in parallel
All resistors 1/4W 1% tolerance

Source

Read more ...

Stereo Preamplifier with Bass-boost

This preamplifier circuit was designed to cope with CD players, tuners, tape recorders etc., providing an ac voltage gain of 4, in order to drive less sensitive power amplifiers. As modern Hi-Fi home equipment is frequently fitted with small loudspeaker cabinets, the bass frequency range is rather sacrificed. This circuit features also a bass-boost, in order to overcome this problem. You can use a variable resistor to set the bass-boost from 0 to a maximum of +16dB @ 30Hz. If a fixed, maximum boost value is needed, the variable resistor can be omitted and substituted by a switch.

Parts List:

P1 - 10K   Log.Potentiometer (Dual-gang for stereo)
P2 - 100K   Log.Potentiometer (Dual-gang for stereo) (See Notes)
R1,R2 - 100K   1/4W Resistors
R3,R6 - 15K   1/4W Resistors
R4 - 10K   1/4W Resistor
R5 - 22K   1/4W Resistor
R7 - 1K   1/4W Resistor
R8 - 560R   1/4W Resistor
C1,C2,C5 - 2µ2   63V Electrolytic Capacitors
C3 - 470µF   35V Electrolytic Capacitor
C4 - 1µF   63V Polyester Capacitor
C6 - 47nF   63V Polyester Capacitor
C7 - 22µF   25V Electrolytic Capacitor
IC1 - TL072  Dual BIFET Op-Amp
SW1 - DPST  Switch (Optional, see Notes)

Notes:

• Schematic shows left channel only, but R1, R2, R3 and C1, C2, C3 are common to both channels.


• For stereo operation P1, P2 (or SW1), R4, R5, R6, R7, R8 and C4, C5, C6, C7 must be doubled.


• Numbers in parentheses show IC1 right channel pin connections.


• A log type for P2 ensures a more linear regulation of bass-boost.


• Needing a simple boost-in boost-out operation, P2 must be omitted and SW1 added as shown in the diagram.


• For stereo operation SW1 must be a DPST type.


• Please note that, using SW1, the boost is on when the switch is open, and off when the switch is closed.
  
  

Source

Read more ...

Stereo PreAmplifier With Tone Control

This is a preamplifier and tone control unit which will make a useful addition to any of our power amplifier circuits. It is extremely easy to construct due to the use of a special IC, The Philips TDA1524A.

Because it uses voltage control, linear single gang pots can be used , which lowers the costs and reduces tracking errors. It also allows for control by switches or microprocessor if desired.

Specification:

D.C. Input : 15V DC supply or 12V

DC battery. 50 mA min.

Maximum output : > 3 V RMS

Maximum input : > 300 mV, G = 20 dB > 3V RMS, G = 0dB

Input Z > 10 k ohm

Output Z < 300 ohm Frequency resp. : <> 50 kHz + / – 1 dB

THD at 1kHz : < 0.1 % at 1V output S/N ratio : > 80 dB, G = 0 dB

Bass boost/cut ~ 15 dB at 50 Hz

Treble boost/cut ~ 15 dB at 15 kHz







Go here for IC TDA1524A Datasheet - Original Audio Kit

Read more ...

USB Powered Audio Power Amplifier for PC

This Power Amplifier might be good solution to all of those who have PC with integrated sound card into motherboard. The main problem is that outputs of such sound cards are for active acoustic systems, this means that speakers must have power amplifier built in. If you decide to connect a headphones sometimes it might be not enough to provide required sound level.

If you are an electronics amateur, you can solve this very easily. You may build your simple power amplifier by using well known Philips operational amplifiers. Lets say we use TDA7053 amplifier. The TDA7053 is an integrated class-B stereo power amplifier in a 16-lead dual-in-line (DIL) plastic package. Which requires minimal amount of external parts. (IC Datasheet)

Read more ...

Low Voltage Audio Power Amplifier LM386

The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.

Features:

• Battery operation


• Minimum external parts


• Wide supply voltage range: 4V-12V or 5V-18V


• Low quiescent current drain: 4mA


• Voltage gains from 20 to 200


• Ground referenced input


• Self-centering output quiescent voltage


• Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8Ohm, PO = 125mW, f = 1kHz)


• Available in 8 pin MSOP package
  
  

The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation. (datasheet)

Read more ...