AV Engineering

Analog vs. Digital Signaling in Professional AV

From transducers to AV-over-IP — a comprehensive engineering reference for conferencing systems

8Sections

5Topics

14Concepts

~2-4 hrsNetworkingAVSignalingAV-over-IPConferencing

01Analog Foundations

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Sine Wave Fundamentals

Every AV signal decomposes into sine-wave components — amplitude, frequency, phase, and wavelength

Every AV signal begins and ends in the analog domain. A microphone capsule converts acoustic pressure waves into a continuously varying voltage; a loudspeaker driver converts amplified voltage back into mechanical motion. All analog signals can be decomposed into sine-wave components via Fourier analysis.

Amplitude

Loudness / Brightness

Composite video: 1 Vp-p into 75 Ω; balanced audio: +4 dBu

Frequency

20 Hz – 20 kHz

Human hearing range; VGA pixel clock up to ~234 MHz

Phase

180° inversion

Balanced audio pin 3 inverts pin 2 for noise rejection

Wavelength

2 – 12 m

At VGA frequencies — moderate cables show transmission-line effects

Analog Signal Types

Video and audio formats still encountered in professional AV

Video

Several analog video formats persist in legacy installations, each with distinct signal characteristics and distance limitations.

Format	Conductors	Level / Impedance	Max Practical Distance
Composite (CVBS)	1 (BNC/RCA)	~1 Vp-p / 75 Ω	~30 m (HD quality)
S-Video	2 (Y + C)	~1 Vp-p / 75 Ω	~15 m
Component (YPbPr)	3 (Y, Pb, Pr)	~1 Vp-p / 75 Ω	~5 m (HD)
VGA (RGBHV)	5 (R, G, B, HSync, VSync)	0–0.7 Vp-p / 75 Ω	~7.5 m at 1920×1200

Audio

Audio connections split into balanced (professional) and unbalanced (consumer) categories, with dramatically different noise rejection and distance capabilities.

Format	Connector	Level	CMRR	Max Distance
Balanced XLR	3-pin XLR	+4 dBu (1.228 V RMS)	60–90 dB	300+ m
Unbalanced RCA	RCA	−10 dBV (0.316 V RMS)	N/A	3–5 m
Unbalanced 3.5 mm	TRS/TS	−10 dBV	N/A	3–5 m

Signal Degradation

What kills analog quality — attenuation, interference, ground loops, and impedance mismatches

Four primary threats degrade analog signal quality. Understanding each threat and its mitigation is essential for reliable AV installations.

Threat	Cause	Mitigation
Attenuation	Signal loss over cable length	Use balanced connections; active extenders for video
EMI/RFI	Proximity to AC power or RF sources	Min 30 cm separation; foil+braid shielding
Ground loops	Multiple ground reference points	Balanced connections, DI boxes, star-ground (AES48)
Impedance mismatch	Deviation from 75 Ω (video)	Proper BNC terminators; matched cable/connectors

Key Analog Metrics

Professional audio: SNR 110–130+ dB (A-weighted), THD+N below 0.001%, crosstalk −80 to −120 dB. Consumer gear: 80–100 dB SNR, 0.01–0.1% THD+N.

The Analog Audio Signal Chain

Five gain stages from microphone to loudspeaker

The analog audio signal flows through five gain stages, each with standardized operating levels that must be maintained for clean signal transfer.

Stage	Level	Key Specs
1. Microphone	−60 to −20 dBu (mic level)	Dynamic: ~−56 dBu; condenser: 48 V phantom (IEC 61938)
2. Preamplifier	+4 dBu (line level)	+20 to +65 dB gain; EIN ≤−128 dBu; THD+N < 0.005%
3. Mixer / DSP	+4 dBu (headroom to +24 dBu)	32/64-bit floating point internal processing
4. Power amplifier	Speaker level (28.3 V RMS @ 100W/8Ω)	Class D: ~90% efficient; Class AB: 50–60%
5. Loudspeaker	4/8/16 Ω or 70V/100V	Sensitivity: 85–100 dB SPL @ 1W/1m

What Remains Analog in 2026

Microphone transduction and speaker conversion are inherently analog. Even Dante-enabled microphones contain internal ADCs. The principle: digitize once at the source, stay digital through all processing, convert to analog only at the final output transducer.

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