Article

Pocket Preamp, part 2

A simple preamplifier with tone control

The PWM power stage discussed in the previous instalment (June 2009) can be used perfectly well on its own. But a matching preamplifier with power supply would complete this amplifier nicely. That is why this month’s Mini Project presents the sequel: the Pocket Preamp.

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PCB

Download Gerber file: 080278-1-V10

Extra info / Update

Main Specifications
- 3-band tone control
- Symmetrical supply
- Compact
- Connector layout matched to associated boards

Component list

Preamplifier board
Resistors
R1 = 220kOhm
R2 = 3.3kOhm
R3 = 10kOhm
R4,R5 = 2.2k
R6 = 15kOhm
R7,R8 = 1.5kOhm
R9 = 4.7kOhm
R10,R11 = 1kOhm
R12 = 1MOhm
R13 = 100Ohm
P1 = 10kOhm potentiometer, logarithmic
P2,P3,P4 = 10kOhm potentiometer, linear
Capacitors
(lead pitch 5mm / 0.2")
C1,C8 = 68pF ceramic
C2 = 180nF polyester / MKT
C3 = 4.7nF polyester / MKT
C4,C5,C6 = 27nF polyester / MKT
C7 = 6.8nF polyester / MKT
C9,C10 = 100nF polyester / MKT
Semiconductors
IC1 = NE5532 (DIP-8)
Miscellaneous
PCB, # 080278-1, from www.thepcbshop.com

Power supply board
Resistors
R1,R2 = 100kOhm
R3,R4 = 1kOhm
Capacitors
C1,C5,C6,C11,C12 = 100nF ceramic, lead pitch 5mm (0.2'')
C2 = 100pF, lead pitch 5mm (0.2'')
C3,C4,C9,C10 = 10µF 63V radial electrolytic, lead pitch 2.5mm (0.1'')
C7,C8 = 4.7µF 63V radial electrolytic, lead pitch 5mm (0.2'')
Inductors
L1 = 10µH axial (vertical mounting)
L2 = 1mH axial (vertical mounting)
Semiconductors
IC1 = TLC555 (DIP-8)
IC2,IC3 = ICL7662CPA+ (DIP-8) (Maxim IC)
Miscellaneous
PCB # 080279-1 from www.thepcbshop.com