• on Audio/Video/Photography
  • Published in issue 10/2009 on page 54
About the article

Pocket Preamp, part 2

A simple preamplifier with tone control

Pocket Preamp, part 2
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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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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 its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update

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

Preamplifier board
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
(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
IC1 = NE5532 (DIP-8)
PCB, # 080278-1, from www.thepcbshop.com

Power supply board
R1,R2 = 100kOhm
R3,R4 = 1kOhm
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'')
L1 = 10µH axial (vertical mounting)
L2 = 1mH axial (vertical mounting)
IC1 = TLC555 (DIP-8)
IC2,IC3 = ICL7662CPA+ (DIP-8) (Maxim IC)
PCB # 080279-1 from www.thepcbshop.com
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