Modulo D
The world’s smallest full-fledged stereo amplifier
The external appearance of this small module with an LC display almost belies what it has inside: a complete stereo preamplifier and final amplifier with IR remote control, adjustable tone, volume and signal levels, and an output power of 2 x 20 W (Class D), all with a single 12-V supply voltage. This makes it perfect for use in a car, boat or motor home.
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Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
Elektor recommends the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.
Extra info / Update
Update
issued: April 7, 2010
Constructors should note that the Modulo-D amplifier will only respond to commands sent by an RC-5 compatible remote control for CD players.
Corrections
issued: April 28, 2010
The schematic in Figure 1 and the parts llst should be corrected as follows
R22,R23 = omit
C15,C24,C31,C32 = 220pF
These corrections do not apply to Modulo D units supplied by Elektor.
Features
- 2 x 20 W continuous output power with 4-Ohm loudspeakers
- remotely controlled bass, treble, volume, and preset signal level
- can be used with RC5-compatible remote control transmitters
- all functions digitally controlled by an ATmega8 microcontroller
- operating status displayed on a three-line LC display with 20 characters per line
- stereo input on Cinch sockets
- auxiliary input on a pin header (selectable under software control)
- display board with IR receiver can easily be fitted separately using a 10-way flat cable
- expansion port for extensions, such as an MP3 player or manual control
- open-source firmware enables individual extensions for specific application areas
- extremely compact because no heat sink is necessary
- dimensions (module without enclosure): 65 x 40 x 35 mm (2.3x1.6x1.4 inch)
- efficiency up to 93%
- operating voltage range 11–14 V
- can be used with an onboard vehicle electrical network or an inexpensive 12-V power supply (4 A min.)
Component list
Resistors
R7 = 0Ohm (SMD0603)
R26,R27,R28,R29 = 10Ohm (SMD0603)
R17, R18 = 22Ohm (SMD0603)
R5 = 100Ohm (SMD0603)
R22,R23 = 180Ohm (SMD0603)
R15,R16 = 2.2kOhm (SMD0603)
R6,R8 = 4.7kOhm (SMD0603)
R9,R10,R19,R20,R21,R22,R24,R25 = 10kOhm (SMD0603)
R1,R2,R3,R4 = 20kOhm (SMD0603)
R11, R12,R13,R14 = 47kOhm (SMD0603)
Inductors
L1,L2,L3,L4,L5 = VHF choke (6-hole ferrite bead)
Capacitors
C44, C45 = 22pF (SMD0603)
C20,C21,C22,C23 = 470pF (SMD0603)
C33,C34 = 5.6nF (SMD0603)
C3,C4,C5,C6,C17,C18,C19,C41,C42,C43,C46,C48 = 100nF (SMD0603)
C35,C38 = 150nF (SMD0603)
C36,C39 = 330nF (SMD0603)
C29,C30,C40,C50,C51,C52 = 470nF (0603)
C1,C2,C7,C9,C10,C13,C14,C15,C24,C25,C26,C27,C28,C31,C32 = 1µF (SMD0603)
C37,C47,C49 = 10µF 16V (SMD tantalum case style B)
C8 = 100µF 16V radial
C11,C12 = 1000µF 16V radial
Semiconductors
D1 = P6SMB16A (SMB)
T1 = BC847 (SOT23)
IC1 = 78L05 (SO8)
IC2 = TSOP34836
IC3 = LD1117-3V3 (SMD SOT223)
IC4 = MAX9744 (MLF44)
IC5 = 78M09 (DPAK)
IC6 = TDA7449 (DIL20)
IC7 = ATMEGA8-16 (TQFP32) (programmed, Elektor order # 090563-41)
X1 = 8MHz quartz crystal (HC49U-V)
Miscellaneous
LCD1 = EA DOGM 163 with backlight
K1, K3, K10, K11= 10-pin receptacle, straight, lead pitch 2.54mm (0.1''), h = 8.5mm
K2 = 10-way flatcable, l = 140mm (5.5'')
K4,K5,K6 = clamp connector SPRINGCON 6-way lead pitch 5.0mm (0.2'')
K7 = expansion port (optional)
K8,K9 = ISP Programming connector for Mega8, 6-pin (2x3) (optional)
K13,K14 = Cinch socket, PCB mount, lead pitch 7.5mm (0.3'')
4 plastic PCB standoffs, l= 4.8mm (0.18'')
20-pin pinheader
Kit of parts with SMD prestuffed boards and all parts, Elektor Shop # 090563-71
PCB design (.pdf); free download
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