Universal I/O for Power Amps

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This two-part circuit was designed as an addition to the 'Compact 200 W Output Stage' in this issue. But it is also suitable for use with IC amplifiers that don't have their own power-on delay.
The circuit consists of an input stage (nothing more than a resistor and capacitor) and a power-on delay with a relay for the amplifier output.
A small PCB has been designed for the input signal. This board contains a phono socket, capacitor and a resistor that is connected directly across the input.

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Materials

054010-PCB.pdf

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.

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PCB

Download Gerber file: 054010-1.zip

Component list

Resistors:
R1 = 270k
R2 = 1k2
R3,R4 = 1M
P1 = 250k preset
Capacitors:
C1 = 4µF7 MKT or MKP (see text)
C2 = 47nF
C3 = 10µF 63V radial
Semiconductors:
D1,D3 = 1N4148
D2 = zener diode 24V 1.3W
D4 = 1N4002
T1 = BS170
Miscellaneous:
K1 = cinch socket, PCB mount, e.g. Monacor / Monarch T-709G
K2, K3 = spade terminal, PCB mount, vertical, 2 pins
RE1 = PCB relay 24 V/16 A (e.g., Omron G2R-1-24, 1100 Ohm, or Schrack RT314024, 1440 Ohm)
PCB, ref. 054010-1