A Hiqh Quality Headphone Amplifier Circuit

Description

Some lovers of High Fidelity headphone listening prefer the use of battery powered headphone amplifiers, not only for portable units but also for home “table” applications. This design is intended to fulfill their needs. An improved output driving capability is gained by making this a push-pull Class-B arrangement. Output power can reach 100mW RMS into a 16 Ohm load at 6V supply with low standing and mean current consumption, allowing long battery duration.

Circuit Diagram

Parts

• P1 = 22K Potentiometer
• R1 = 15K Resistor
• R2 = 100K Resistor
• R3 = 100K Resistor
• R4 = 47K Resistor
• R5 = 470R Resistor
• R6 = 500R Resistor
• R7 = 1K Resistor
• R8 = 18K Resistor
• R9 = 18K Resistor
• R10 = 2.2R Resistor
• R11 = 2.2R Resistor
• R12 = 33R Resistor
• R13 = 4.7K Resistor
• C1 = 10uF-25V Capacitors
• C2 = 10uF-25V Capacitors
• C3 = 100nF-63V (PF)
• C4 = 220uF-25V Capacitors
• C5 = 100nF-63V (PF)
• C6 = 220uF-25V Capacitors
• Q1 = BC560C PNP Transistor
• Q2 = BC560C PNP Transistor
• Q3 = BC550C NPN Transistor
• Q4 = BC550C NPN Transistor
• Q5 = BC560C PNP Transistor
• Q6 = BC327 PNP Transistor
• Q7 = BC337 NPN Transistor
• J1 = RCA Audio Input Socket
• J2 = 3mm Stereo Jack Socket
• B1 = 6V Battery Rechargeable
• SW1=SPST Slide or Toggle Switch

Notes:

• For a Stereo version of this circuit, all parts must be doubled except P1, SW1, J2 and B1.
• Before setting quiescent current rotate the volume control P1 to the minimum, Trimmer R6 to maximum resistance and Trimmer R3 to about the middle of its travel.
• Connect a suitable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output.
• Switch on the supply and measure the battery voltage with a Multimeter set to about 10Vdc fsd.
• Connect the Multimeter across the positive end of C4 and the negative ground.
• Rotate R3 in order to read on the Multimeter display exactly half of the battery voltage previously measured.
• Switch off the supply, disconnect the Multimeter and reconnect it, set to measure about 10mA fsd, in series to the positive supply of the amplifier.
• Switch on the supply and rotate R6 slowly until a reading of about 3mA is displayed.
• Check again the voltage at the positive end of C4 and readjust R3 if necessary.
• Wait about 15 minutes, watch if the current is varying and readjust if necessary.
• Those lucky enough to reach an oscilloscope and a 1 KHz sine wave generator can drive the amplifier to the maximum output power and adjust R3 in order to obtain a symmetrical clipping of the sine wave displayed.

Technical data:
Output power (1 KHz sine wave):

• 16 Ohm: 100mW RMS
• 32 Ohm: 60mW RMS
• 64 Ohm: 35mW RMS
• 100 Ohm: 22.5mW RMS
• 300 Ohm: 8.5mW RMS

Sensitivity:

• 160mV input for 1V RMS output into 32 Ohm load (31mW)
• 200mV input for 1.27V RMS output into 32 Ohm load (50mW)

Frequency response at 1V RMS:

• Flat from 45Hz to 20 KHz, -1dB at 35Hz, -2dB at 24Hz

Total harmonic distortion into 16 Ohm load at 1 KHz:

• 1V RMS (62mW) 0.015% 1.27V RMS (onset of clipping, 100mW) 0.04%

Total harmonic distortion into 16 Ohm load at 10 KHz:

• 1V RMS (62mW) 0.05% 1.27V RMS (onset of clipping, 100mW) 0.1%
• Unconditionally stable on capacitive load

 Source: http://www.redcircuits.com

09:17 0 comments

Improved 3 Transistor Audio Amp (80 milliwatt) Circuit

Description

This circuit is similar to the 3 Transistor Audio Amp but uses positive feedback to get a little more amplitude to the speaker. I copied it from a small 5 transistor radio that uses a 25 ohm speaker. In the circuit above, the load resistor for the driver transistor is tied directly to the + supply. This has a disadvantage in that as the output moves positive, the drop across the 470 ohm resistor decreases which reduces the base current to the top NPN transistor. Thus the output cannot move all the way to the + supply because there wouldn't be any voltage across the 470 resistor and no base current to the NPN transistor.

This circuit corrects the problem somewhat and allows a larger voltage swing and probably more output power, but I don't know how much without doing a lot of testing. The output still won't move more than a couple volts using small transistors since the peak current won't be more than 100mA or so into a 25 ohm load. But it's an improvement over the other circuit above.

In this circuit, the 1K load resistor is tied to the speaker so that as the output moves negative, the voltage on the 1K resistor is reduced, which aids in turning off the top NPN transistor. When the output moves positive, the charge on the 470uF capacitor aids in turning on the top NPN transistor.

The original circuit in the radio used a 300 ohm resistor where the 2 diodes are shown but I changed the resistor to 2 diodes so the amp would operate on lower voltages with less distortion. The transistors shown 2n3053 and 2n2905 are just parts I used for the other circuit above and could be smaller types. Most any small transistors can be used, but they should be capable of 100mA or more current. A 2N3904 or 2N3906 are probably a little small, but would work at low volume.

The 2 diodes generate a fairly constant bias voltage as the battery drains and reduces crossover distortion. But you should take care to insure the idle current is around 10 to 20 milliamps with no signal and the output transistors do not get hot under load.

The circuit should work with a regular 8 ohm speaker, but the output power may be somewhat less. To optimize the operation, select a resistor where the 100K is shown to set the output voltage at 1/2 the supply voltage (4.5 volts). This resistor might be anything from 50K to 700K depending on the gain of the transistor used where the 3904 is shown

Circuit Diagram

Source-http://www.electronguide.com/circuits_pages/Improved3TransistorAudioAmp.html

07:21 0 comments

Audio Amplifier with High Clarity Circuit Diagram

Circuit Diagram

Description

The heart of the circuit is TDA7294 which acts as an amplifier the right and left input feded from the pre amplifier circuit is amplified after passing through the noise filter which contains an RC circuit, the volume is controlled by the variable resistor 47k. and the automatic gain control is provided by the operational amplifier circuit opp amp IC249 For both right channel and left channel., the speaker used is an 8 ohms 40 watts speaker. 

Source -http://www.electronguide.com/circuits_pages/AudioAmplifier.html

08:06 0 comments

Power Amplifier Circuit Diagram with 2n3055

Circuit Diagram

Description

Simple and low cost. The optimal accumulation voltage is about 50V, but this amp assignment from 30 to 60V. The acute ascribe voltage is about 0.8 – 1V. As you can see, in this architecture the apparatus accept a big tolerance, so you can body it about of the components, which you acquisition at home. The and transistors can be any NPN blazon ability transistor, but do not use Darlington types… The achievement ability is about 60W.

Descriptions:

- capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequncies are accepting louder.

- capacitor C2 regulates the college frequencies (treble), as the capacitance grows, the college frequencies are accepting quiter.

- this is a chic B amplifier, this means, that a accepted charge breeze through the end transistors, alike if there is no arresting on the input. This accepted can be adapted with the 500Ω trimmer resistor. As this accepted incrases, the complete of the amplifier gets better, but the end transistors are added heating. But if this accepted decrases, the transistors are not heating so much, but the complete gets worse…

Source - http://skemarangkaian.com/power-amplifier-circuit-with-2n3055/

11:49 0 comments

300W Subwoofer Amplifier Circuit Diagram

Description

This is an amplifier circuit that is formed from a transistor amplifier miraculous. This circuit is used in the speaker subwoofer with 300W maximum power on each side. To apply it, can be used in the room that is not too large, like the car. And the voltage needed between 25 to 42 Volt DC.

Circuit Diagram 

Source-http://gambarskemarangkaian.blogspot.in/2011/04/300w-subwoofer-amplifier-schematic.html

09:56 0 comments