Dual 20 Watt Audio Power Amplifier

Overture Audio Power Amplifier Series Dual 20-Watt Audio Power Amplifier with Mute and Standby Modes
 

The LM1876 is a stereo audio amplifier capable of delivering typically 20W per channel of continuous average output power into a 4 or 8 load with less than 0.1% THD+N. Each amplifier has an independent smooth transition fade-in/out mute and a power conserving standby mode which can be controlled by external logic.

The performance of the LM1876, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe™) protection circuitry, places it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA). SPiKe protection means that these parts are safeguarded at the output against overvoltage, undervoltage, overloads, including thermal runaway and instantaneous temperature peaks.

Dual 20-Watt Audio Power Amplifier Circuit Diagram

Key Specification

THD+N at 1kHz at 2 x 15W continuous average
output power into 4 or 8:	0.1% (max)
THD+N at 1kHz at continuous average
output power of 2 x 20W into 8:	0.009% (typ)
Standby current:	4.2mA (typ)

Applications :

High-end stereo TVs

Component stereo

Compact stereo
Features :

SPiKe protection

Minimal amount of external components necessary

Quiet fade-in/out mute mode

Standby-mode

Isolated 15-lead TO-220 package

Non-Isolated 15-lead TO-220 package

Wide supply range 20V - 64V 

Read More

2N3055 and LM317 power supply regulatable 0 28V 20 Amp

Part list for 20 Ampere regulatable power supply:

• 2 x 15 volt 20+- amps
• D1…D4= Bridge rectifier MB2504 (25 amps cooled)

  or eight BYW29 8 amp diodes (TO220 pinning cooled)
  or 8 x MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 16 x 1N5401 (1N5408) diodes.

• F1 = 2 Amp
• F2 = 25 amp
• R1 2k2 2,5 Watt
• R2 240 ohm
• R3,R4,R5,R6 0.1 ohm 10 watt
• R7 6k8
• R8 10k
• R9 47 Ohm 1 watt
• S2 mini switch
• R10 8k2
• C1,C7,C9 47nF
• C2 four times 4700uF/50v or one 22000uF/50v
• C3,C5 10uF/50v
• C4,C6,C9 100nF
• C8 330uF/50v
• C10 1uF/16v
• D5 1N4151
• D6 1N5401
• D10 MR750
• D11 LED
• D7, D8, D9 1N4001
• IC1 LM317
• Two 2N3055 transistors
• P1 5k
• P3 10k trimmer
• relay = 30 volts AC, 2×10 amp switching

S2 switches between +- 3 Amps and full output current

The relay is used to switch off the power supply voltage when the mains (S1) are/is switched off. So no delay do to the discharge of C2, and so preventing output voltages from not return to zero immediately.

A MB2504 is used as it is a 25 ampere rectifier bridge which also should be cooled. Or you could use eight BYW29 8 amp diodes (TO220 pinning) mounted on a heat sink.

Mount a little heatsink on the LM317 IC

Remember to isolate the 2N3055 transistors from the chassis/radiator! Use a radiator (heat sink) of appropriate size and surface area; insulating and heat-conducting spacer or at least a thin mica; hot adhesive and thermal paste.

Read More