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Sound Pressure Level (SPL) Meter
the king-sized model
The measuring instrument described here distinguishes itself in one respect from all the others in its species. The display has been implemented in such a way that is – without exaggeration – not easily overlooked. This opens up entirely new possibilities for its application.The most salient feature of this circuit is that the display consists of a panel made from 10 incandescent lamps. This immediately catches the eye, and at the same time it is obvious that we’re dealing with a novel kind of measuring instrument. A typical sound pressure or VU meter makes use of a much more modest LED or moving coil indicator.
Materials
Component list
Resistors:
R1,R9 = 10k?
R2 = 220?
R3 = 27k?
R4,R7 = 100k?
R5 = 3k?9
R6 = 3k?3
R8 = 39k?
R10 = 5k?6
R11 = 220k?
R12,R13,R14 = 10k?0
R15,R16 = 20k?0
R17 = 47k?
R18 = 1k?00
R19 = 30k?9
R20,R21 = 820?
R22-R31,R34 = 100?
R32 = 1k?2
R33 = 470?
R35 = 4?7
R36 = 2k?7
P1 = 500k? preset
P2 = 500? preset
Capacitors:
C1,C2 = 22µF 40V radial
C3,C14 = 470µF 16V radial
C4 = 15pF
C5 = 56nF, lead pitch 5mm
C6 = 2n7, lead pitch 5mm
C7 = 4n7, lead pitch 5mm
C8 = 8n2, lead pitch 5mm
C9 = 10 n, lead pitch 5mm
C10,C11 = 2µF2 63V radial
C12 = 100nF
C13 = 100nF, lead pitch 5mm
C15 = 1000µF 6V3 radial
C16 = 470µF 10V radial
C17 = 10µF 63V radial
C18 = 470µF 25V radial
Semiconductors:
D1-D10 = LED, red (no highefficiency type)
D11 = 1N4148
D12 = BAT85
D13 = LED, green (high-efficiency)
IC1 = TLC274
IC2 = TLC272
IC3,IC4 = LM3915
IC5...IC14 = S202S02 (Sharp)
IC15 = 7808
Miscellaneous:
JP1 = 2-way pinheader w. jumper
JP2 = 3-way pinheader w. jumper
K1-K11 = 2-way PCB terminal block, lead pitch 7.5 mm
K12 = cinch socket, chassis mounting
Tr1 = 9V 4VA8 e.g., Gerth 421.09
B1 = B80C1500 in rectangular case (80V piv, 1.5A peak)
F1-F10 = fuse, 500mA, fast, with PCB mount holder
MIC1 = MCE2000 (Monacor/Monarch) or equivalent
F11 = fuse, 32 mA, slow, with PCB mount holder
PCB, order code 020122-1
R1,R9 = 10k?
R2 = 220?
R3 = 27k?
R4,R7 = 100k?
R5 = 3k?9
R6 = 3k?3
R8 = 39k?
R10 = 5k?6
R11 = 220k?
R12,R13,R14 = 10k?0
R15,R16 = 20k?0
R17 = 47k?
R18 = 1k?00
R19 = 30k?9
R20,R21 = 820?
R22-R31,R34 = 100?
R32 = 1k?2
R33 = 470?
R35 = 4?7
R36 = 2k?7
P1 = 500k? preset
P2 = 500? preset
Capacitors:
C1,C2 = 22µF 40V radial
C3,C14 = 470µF 16V radial
C4 = 15pF
C5 = 56nF, lead pitch 5mm
C6 = 2n7, lead pitch 5mm
C7 = 4n7, lead pitch 5mm
C8 = 8n2, lead pitch 5mm
C9 = 10 n, lead pitch 5mm
C10,C11 = 2µF2 63V radial
C12 = 100nF
C13 = 100nF, lead pitch 5mm
C15 = 1000µF 6V3 radial
C16 = 470µF 10V radial
C17 = 10µF 63V radial
C18 = 470µF 25V radial
Semiconductors:
D1-D10 = LED, red (no highefficiency type)
D11 = 1N4148
D12 = BAT85
D13 = LED, green (high-efficiency)
IC1 = TLC274
IC2 = TLC272
IC3,IC4 = LM3915
IC5...IC14 = S202S02 (Sharp)
IC15 = 7808
Miscellaneous:
JP1 = 2-way pinheader w. jumper
JP2 = 3-way pinheader w. jumper
K1-K11 = 2-way PCB terminal block, lead pitch 7.5 mm
K12 = cinch socket, chassis mounting
Tr1 = 9V 4VA8 e.g., Gerth 421.09
B1 = B80C1500 in rectangular case (80V piv, 1.5A peak)
F1-F10 = fuse, 500mA, fast, with PCB mount holder
MIC1 = MCE2000 (Monacor/Monarch) or equivalent
F11 = fuse, 32 mA, slow, with PCB mount holder
PCB, order code 020122-1
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