Showing posts with label Powered. Show all posts
Showing posts with label Powered. Show all posts
Thursday, November 6, 2014
Battery powered Headphone Amplifier
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 fulfil their needs and its topology is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage.
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. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.
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. The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.
Battery-powered Headphone Amplifier Circuit Diagram:
- 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 1KHz 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.
Output power (1KHz sinewave):
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 @ 1V RMS:
flat from 45Hz to 20KHz, -1dB @ 35Hz, -2dB @ 24Hz
Total harmonic distortion into 16 Ohm load @ 1KHz:
1V RMS (62mW) 0.015% 1.27V RMS (onset of clipping, 100mW) 0.04%
Total harmonic distortion into 16 Ohm load @ 10KHz:
1V RMS (62mW) 0.05% 1.27V RMS (onset of clipping, 100mW) 0.1%
Unconditionally stable on capacitive loads
Thursday, October 30, 2014
Stereo PC Speaker Powered USB Speaker
This is the circuit diagram of USB powered computer speaker, or it widely known as multimedia speakers for PCs. The circuit has single-chipbased design, low-voltage electrical power supply, compatibility with USB power from computer, simple heat-sinking, inexpensive, large flexibility and wide temperature tolerance.
At the heart of the circuit is IC TDA2822M. This IC is, actually, monolithic type in 8-lead mini DIP (Dual Inline Package). It’s designed for use as a dual audio power amplifier in battery powered sound players. Features of TDA2822M are very low quiescent current, low crossover distortion, DC source voltage down to 1.8 volts and minimal output power of approximately 450 mW/channel with 4 ohm loudspeaker at 5V DC supply input.
An ideal power amplifier can be basically described as a circuit which can supply audio power into external loads without having producing substantial signal distortion and without having consuming extreme quiescent current.
This circuit is powered by 5V DC source obtainable from the USB port of the Computer. When electrical power switch S1 is turned to ‘on’ position, 5V power supply is extended towards the circuit and power indicator red LED1 illuminates immediately. Resistor R1 is actually a current surge limiter and capacitors C1 and C4 work as buffers.
How the circuit works..?
The operation of the circuit is very simple. Audio signals from the Computer audio port or headphone port are fed towards the amplifier circuit via R2 and C2 (for left channel), and R3 and C3 ( forright channel). Potensiometer VR1 used as the volume controller for left (L) channel, while potensiometer VR2 used to control the volume level of right (R) channel. Pin 7 of TDA2822M receives the left channel sound signals and pin 6 receives the right channel signals by way of VR1 and VR2, correspondingly. Amplified signals for driving the left and right loudspeakers can be obtained at pins 1 and pin 3 of IC1, correspondingly. Components R5 and C8, and R6 and C10 form the classic zobel network.
Construct the circuit on a medium size, general purpose PCB and enclose inside a appropriate case. It really is recommended to utilize a socket for IC TDA2822M. The external connections ought to be made working with suitably screened wires for improved result.
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