Preamplifier 2012 (1)

Part 1: introduction and line-in/tone/volume board

Published in issue 4/2012 on page 16

Besides presenting a truly high end audio control preamplifier for home construction, this article series also aims to show how low-impedance design and multiple-amplifier techniques can be used to significantly reduce the noise levels in analogue circuitry. The result of the design effort is a top-notch preamp that’s brilliant not just sonically but also in terms of cost/performance ratio.

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(1% tolerance; metal film; 0.25W)
R1,R2,R39,R40 = 100Ohm
R3-R6,R41-R44,R78,R79 = 100kOhm
R45-R50,R54,R55,R59-R62,R71,R72 = 1kOhm
R13,R51 = 470Ohm
R14,R15,R52,R53 = 430Ohm
R18,R35,R36,R56,R73,R74 = 22kOhm
R19,R20,R57,R58 = 20Ohm
R25-R28,R63-R66 = 3.3kOhm
R29-R32,R67-R70 = 10Ohm
R37,R38,R75,R76 = 47Ohm
R77 = 120Ohm
P1,P2,P3,P4 = 1kOhm, 10%, 1W, stereo potentiometer, linear law, e.g. Vishay Spectrol cermet type 14920F0GJSX13102KA. Alternatively, Vishay Spectrol conductive plastic type 148DXG56S102SP (RS Components p/n 484-9146).
C1,C2,C10-C14,C26,C27,C35-C39 = 100pF 630V, 1%, polystyrene, axial
C3,C4,C28,C29 = 47µF 35V, 20%, bipolar, diam. 8mm, lead spacing 3.5mm, e.g. Multicomp p/n NP35V476M8X11.5
C5,C6,C30,C31 = 470pF 630V, 1%, polystyrene, axial
C7,C32 = 1µF 250V, 5%, polypropylene, lead spacing 15mm
C8,C9,C33,C34 = 100nF 250V, 5%, polypropylene, lead spacing 10mm
C15,C16,C40,C41 = 220µF 35V, 20%, bipolar, diam. 13mm, lead spacing 5mm, e.g. Multicomp p/n NP35V227M13X20
C17-C25,C42-C50 = 100nF 100V, 10%, lead spacing 7.5mm
C51 = 470nF 100V, 10%, lead spacing 7.5mm
C52,C53 = 100µF 25V, 20%, diam. 6.3mm, lead spacing 2.5mm
IC1,IC3,IC5-IC10,IC12,IC14-IC18 = NE5532, e.g. ON Semiconductor type NE5532ANG
IC2,IC4,IC11,IC13 = LM4562, e.g. National Semiconductor type LM4562NA/NOPB
K1-K4 = 4-pin straight pinheader, pitch 0.1’’ (2.54mm), with mating sockets
K5,K6,K7 = 2-pin pinheader, pitch 0.1’’ (2.54mm), with mating sockets
JP1 = 2-pin pinheader, pitch 0.1’’ (2.54mm), with jumper
K8 = 3-way PCB screw terminal block, pitch 5mm
RE1,RE2 = relay, 12V/960Ohm, 230VAC/3A, DPDT, TE Connectivity/Axicom type V23105-A5003-A201
PCB # 110650-1
Note: all parts available from Farnell (but not exclusively), except PCB 110650-1.