Download Basic Audio Electronics Document

MODERN ENGINEERING GROUP
BASIC AUDIO ELECTRONICS
Tuesday, December 15, 2015
Note: This document is not to be distributed by email, copies or otherwise duplicated and/or reproduced
without the written consent of Modern Ebgineering Group.
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By: Nigel Redman, CTO
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TOPICS: SPEAKER CONFIGURATIONS, AUDIO POWER LEVELS, SPEAKER DRIVERS, PHASING
Speaker Conventions – as they relate to Amplifiers
Ohms: 4, 8, etc 70V, 25V : Constant Current vs. Constant Voltage
Switches 2, 4 6, position - Ohms required at Amp
Series, Parallel speaker circuits
Impedance Conventions
Examples – Headphones, Microphones, Line Level
Amplifier Outputs: transformer, Op-amp
how do all these relate?
Cable Shop Wiring Conventions
¼” TS to XLR to RCA to 3.5m TS, TRS, ¼”TRS
How exactly do we wire these various cables?
What can go wrong if they are wired incorrectly?
INFORMATION: MATCHING IMPEDANCE USING OHMS LAW FOR PARALLEL & SERIES CONFIGURATIONS.
P=POWER, V=VOLTAGE, I=CURRENT
1.
2.
3.
4.
2 SPEAKERS OF SAME IMPEDANCE IN PARALLEL THE VALUE OF ONE DIVIDED BY THE QUANTITY(2): EX: FIG. D
2 SPEAKERS IN SERIES THE VALUES ARE ADDED: EX: FIG. B
4 SPEAKERS WIRED IN SERIES-PARALLEL EQUAL 8 OHMS EX: FIG A
4 SPEAKERS WIRED IN SERIES-PARALLEL EQUAL 8 OHMS EX: FIG C(PARALLEL OF 2 SERIES PAIRS)
FIG A
FIG D
FIG B
FIG C
70 VOLT SPEAKER SYSTEMS
TYPICAL SPEAKER 70V TRANSFORMER
70VOLT LINE TRANSFORMERS
TYPICAL 70V SPEAKER AMPLIFIER
AUDIO SIGNAL LEVELS
signal type
voltage current
line-level, typical professional equipment 1.23V
line-level, typical home/hifi
0.316V
.1W into 8-ohm speakers
.894V .112A
1W into 8-ohm speakers
2.83V .354A
10W into 8-ohm speakers
8.94V 1.12A
100W into 8-ohm speakers
28.3V 3.54A
1000W into 8-ohm speakers
89.4V 11.2A
CURRENT ACROSS SPEAKERS BASED ON IMPEDANCE
signal type
.1W into 8-ohm speakers
voltage current
.894V .112A
1W into 8-ohm speakers
2.83V .354A
10W into 8-ohm speakers
8.94V 1.12A
100W into 8-ohm speakers 28.3V 3.54A
1000W into 8-ohm speakers 89.4V 11.2A
1000W into 4-ohm speakers 63.2V 15.8A
1000W into 2-ohm speakers 44.7V 22.4A
1000W into 1-ohm speakers 31.6V 31.6A
LINE LEVEL AUDIO
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Typical professional equipment uses level +4dBu (unloaded), which is 1.23V
The German studio standard is +6dBu, which is 1.55V, but that does not mean all professional equipment
provides such a high level
Typical home/hifi equipment uses -10dBV, which is 0.316V
For calculation of this type, see see http://www.sengpielaudio.com/Rechner-db-volt.htm
The currents are very small because in audio equipment, for minimum distortions and best frequency
response, you use low output impedance of sender and high input impedance of receiver.
SPEAKER PHASING AND WIRING FOR PROPER PHASING:
WRONG PHASING
PROPER PHASING
SERIES
IN PHASE SERIES POINTED IN
PROPER PHASING PARALLEL
IN PHASE PARALLEL POINTED IN
AMPLIFIER CLIPPING/DISTORTION:
GAIN OF 3 NO CLIP
GAIN OF 4 CLIPPING