Wiring Schematic Diagram

A CD-ROM drive can be used as a stand-alone unit for playing digital audio CDs without interfacing with a computer. The stereo output of CD player available at the audio jack can be amplified using audio input facility which is normally available on a tape-deck/tape-recorder or a stereo amplifier. Audio socket on front/rear of the CD-ROM drive is capable of driving headphones or speakers of less than 500mW. Proper stereo jacks for interconnection between CD-ROM drive and tape deck are available from computer/tape recorder spares vendors. The principle of operation is illustrated here with the help of block diagram.

The 4-pin power supply socket available at the rear of a CD-ROM player is meant for +5V, ground (two middle pins) and +12V inputs. The power supply can be easily derived using a conventional power supply circuit as shown in the figure. If you have an external CD-ROM drive, it can be simply plugged into the mains since it has self-contained power supply circuit inside.

While there may be minor differences amongst the available CD-ROM drives’ external controls, a typical drive’s controls are shown in the figure here. Please ensure that a proper power supply connector available from computer spare parts vendor is used for connection to CD-ROM drive. To identify +5V and +12V pins on the drive connector, please note that in the computer +12V is routed using a yellow wire and for +5V a red wire is used, while for ground black wires are used with the supply connector. Once the power supply has been connected correctly, you will notice that LED indicator on the drive starts flashing. Now the digital audio CD can be loaded after pushing the eject button. A second push of the same button causes retraction of CD carriage into the drive. One can change the track (song) on the CD using play switch on the CD-ROM drive.

Source :ELECTRONICS PROJECTS Vol. 20

Note:

• The Pre-amp Circuit can be powered from a 12V battery or 12V DC power supply.
• Up to 24 V DC can be used to power the circuit.

Simple  FET  Audio Mixer

• As many or as few channels as are required can be added to the mixer. Do this by just duplicating the input "sections" which are clearly shown on the schematic. One version of this mixer I saw had 25 inputs!
• A shielded case is probably needed to reduce hum and help stop oscillations.
• The circuit can be powered by a single 9 volt battery.

R1, R3     : 10K Pot
R2, R4     : 100K 1/4 W Resistor
R5         : 6.8K 1/4 W Resistor
C1, C2, C3 : 0.1uF Capacitor
Q1         : 2N3819 Junction FET

The LM3876 is a high-performance audio power amplifier capable of delivering 56W of continuous average power to an 8 load with 0.1% THD+N from 20Hz-20kHz.The performance of the LM3876, utilizing its Self Peak Instantaneous Temperature protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area. Speaker protection means that these parts are completely safeguarded at the output against overvoltage, undervoltage, overloads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks.The LM3876 maintains an excellent signal-to-noise ratio of greater than 95dB (min) with a typical low noise floor of 2.0µV. It exhibits extremely low THD+N values of 0.06% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an typical rating of 0.004%.

Features

• 56W continuous average output power into 8Ω

• 100W instantaneous peak output power capability

• Signal-to-Noise Ratio >= 95 dB(min)

• An input mute function

• Output protection from a short to ground or to the supplies via internal current limiting circuitry

• Output over-voltage protection against transients from inductive loads

• Supply under-voltage protection, not allowing internal biasing to occur when V_EE + V_CC <= 12V, thus eliminating turn-on and turn-off transients

• 11-lead TO-220 package

• Wide supply range 20V - 94V

Part list

Resistor:
R1, R3 = 1 k
R2, R4, R5 = 18k
R6 = see text
R7 = 10R, 5 Watt
R8, R9 = 22k

Capacitors:
C1 = 2.2 uF
C2 = 220 uF, 160 V
C3 = 22 uF, 40 V
C4 = 47 pF
C5 = 100 uF, 40 V
C6 = see text
C7, C8 = 100 nF
C9, C10 = 1000 uF, 40 V
Inductors:
L1 = 0.7 uH – see text

Integrated circuits:
IC1 = LM3876T

Miscellaneous:
Heat sink for IC1

Air-cored inductor L1 consists of 13 turns of 1mm dia. enamelled copper wire with an inner diameter of 10mm. The completed inductor is pushed over R7 and its terminals soldered to those of the resistor. All electrolytic capacitors must be mounted upright. The amplifier can be muted with a single-pole switch connected to the MUTE input (pin8). This function is enabled when the switch is open. If muting is not required, solder a wire bridge across the mute terminals on the board. The R6-C6 is not normally required in this application, but provision has been made for it for use in other applications. According to the manufacturers, both chips are optimalized for a load of 8 Ohm. The output power is lower when a 4 Ohm load is used or when the supply voltage is reduced. When a 4 Ohm load is used, the SPIKE protection becomes active when the supply voltage is about 27V, resulting a in a reduction of the power output to 10W. This means that it is not advisable to use loudspeaker with an impedance