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Ed's AV Handbook
Batting Practice for the AV Professional
and primer for the novice

Chapter 5  Page 1

The AV System Sequence
Conform or Perish

The AV System Sequence is a one-way path from a selected source to the component that reproduces its sound and or video.  It is a process where conformity is mandatory as exists lead only to entrances.  Non-conformity will result in silence and a blank video screen.  A clear grasp of the sequence fosters efficient system setup and minimizes time spent diagnosing problems.  Prepare to submit to the electron flow of the AV System Sequence.

The Sequence

Source  >  Preamplifier  >  Amplifier  Speaker and or TV / Projector

Source

An audio or video source is the initial component of the sequence.  Audio and video sources include compact disc players, turntables, DVD players, BluRay players, cable boxes, satellite receivers, Internet streaming devices, AM/FM tuners, audio cassette decks, game consoles, off-air television tuners, Bluetooth devices, etc. 
CD Player Rear Panel
Each source has output jacks that feed the input jacks of the next step in the sequence via -- HDMI, single-ended RCA, optical Toslink, or balanced XLR -- interconnecting cable.  Wireless Bluetooth and WiFi sources transmit to Bluetooth and WiFi receivers of the next sequence step.

*Audio or AV Preamplifier

The next step in the sequence path is the audio and or audio/video preamp.  Sources enter the preamp via dedicated labeled input jacks or wireless Bluetooth and WiFi receivers.  The preamp switches between connected sources via a knob or row of buttons on the preamp front panel.
NAD AV Pre Pro
Prior to the exiting the output jacks, selected sources are manipulated and or processed via another knob, buttons, or the setup menu. 
Manipulation includes volume, bass/treble control, equalization.  Processing includes surround formats, digital audio formats, video scaling, video trans-coding. 
The selected source is then routed to the next step in the sequence.

Audio or Video Amplifier

The Audio Amplifier

The audio preamp output jacks connect to the input jacks of the amplifier. 
The amplified audio then continues to the speaker connecting output jacks.

Amp Rear Panel

The Video Amplifier

The AV preamp video output connects to the video input of a TV or projector. 
Video amplification is integrated with the TV video decoding circuitry.

Back Panel Sony TV


The Speaker ...........

The amplifier output speaker jacks are connected to the speaker input jacks.
The speaker modulating speaker cone that reproduces the ultimate sound waves.

Rear Panel Spk Jacks

........ and or TV/Projector

The AV preamp output connects (typically via an HDMI interconnect) to the TV or projector input jack.
The combined output of the TV video decoder/amplifier illuminates the pixel elements of the TV or projector.

Rear Panel Sony Projector



Sequence confusion, audio adjustment, and three additional notes.

1. TV Confusion
The television can add confusion.  TVs include additional input jacks plus "The Sequence" of an off-air-TV-tuner source > switching pre-amp > amplifier > speaker and TV screen.  This permits the TV to perform as a stand-alone low-fidelity audio plus video system.  

2. *Pre-amp Adjustment
Many audio pre-amps and receivers have eliminated the phono preamp stage.  If a turntable is in play, then a dedicated-phono-pre-amp must be added and inserted to the input of the pre-amp.  The phono pre-amp boosts phono cartridge voltage and provides RIAA specified playback equalization.

3. Sequence Note
A stereo or AV receiver is a source AM/FM tuner + pre-amp + amplifier in one cabinet.
An integrated amplifier is a pre-amp + amplifier in one cabinet.
A portable radio is an AM/FM tuner + pre-amp + amplifier + speaker in one very small cabinet.

4. Video Sequence Route Note
The video source determines the interconnect path to the TV.  Contemporary product is widely limited to HDMI cabling.  However, legacy product may employ composite video, component video, or RGB interconnects.  If you start a sequence with composite video, then composite cabling must continue to the TV.  If component cable, then component cable must complete the sequence.

Multiple types of cabling requires multiple hookup paths to the TV, and video source switching, unless the receiver/preamp includes video transcoding. 
Typical transcoding converts composite and component video to HDMI.   However, transcoding has disappeared from many current AV receivers.  Therefore, ask customers if they plan to use legacy video sources.  Then choose the appropriate receiver/preamp.

5.Interconnect Jack Note
Each sequence step described connection via outputs and inputs jacks.  Integrated devices (as in Note #3) are connected on their PC boards.


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Ed's AV Handbook   
Copyright 2007 Txu1-598-288 Revised 2021


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