FIELD GUIDESource-led reference
Port & Cable

Microphones / interfaces / monitors / headphones

Follow the audio signal.

A reference desk for exact analog endpoints, channel allocation and the questions a connector shape cannot answer.

Begin with the connection you are investigating

Four audio questions

Separate the physical component from equipment service, optical requirements and the information still needed. These references do not approve an installation.

  1. Why can a TRRS headset fail in an audio socket?
  2. Is a TRS socket for headphones or balanced line audio?
  3. Does an XLR shell identify audio, control or power?
  4. Why can an optical cable fit but produce no usable audio?

Decision field guide 06 Optical versus electrical

The optical path is not an analog jack

TOSLINK and Mini-TOSLINK are optical forms. A similar-sized 3.5 mm metal-contact plug is not evidence of optical capability.

Conceptual optical versus electrical decision path; steps and conditions appear in the text equivalent alongside. Illustration not to scale or a compatibility finding.
Original explanatory schematic · not to scale · read the exact source scope. Scroll horizontally on small screens.

Read the decision

  1. Confirm both endpoints expose optical output/input, not just a 3.5 mm opening.
  2. Match full-size TOSLINK and Mini-TOSLINK ends to the documented physical optical ports.
  3. Check supported digital audio format and channel mode; a physically matching optical cable does not settle ADAT versus S/PDIF.

Still unknown: The diagram does not claim that every optical port supports every optical audio format.

Compare the optical connectors

Existing evidence: C024A · C025A · C323A source records S845 · S405 · S380. See each source record for its inspection date and scope; graphic interpretation remains pending independent technical and publication review.

FOLLOW THE AUDIO SIGNAL

The plug is only
the beginning.

Give the signal a role. Give each channel a destination. Keep power, cable evidence and shared inputs in view.

Check an audio path →Find an exact model
01 / SOURCEWhat leaves this output?Microphone · line · instrument · headphones
02 / PATHWhat does the cable preserve?Layout and exact cable evidence stay separate
03 / DESTINATIONWhich physical input receives it?Shared channels count only once
8 exact model profiles21 endpoint presentations6 practical guides0 automatic power actions

Plan more than one connection

Audio patch sheet

Assign anonymous physical units, reserve shared inputs, and find contradictory observations. Up to twelve explicit paths; no hidden cable or power assumptions.

Find the exact model

Audio device directory

Microphones, interfaces, active monitors, headphones and a passive direct box. Inspect source-linked endpoints before opening a worksheet.

Three useful distinctions

Same outline. Different job.

Balanced mono ≠ stereo

The 2i2’s rear line outputs and front headphone output use TRS sockets for different roles.

S138

Two jacks ≠ two channels

An HS5’s XLR and TRS inputs are alternatives on one physical speaker, not two independent channels.

S144

Available power ≠ observed power

The 2i2’s supply covers both XLR inputs. The worksheet never decides a physical switch state for you.

S137

Build your understanding, one path at a time.

Practical guide / P149

Audio connections: identify the signal before the plug

A connector outline does not tell you whether a signal is microphone, line, instrument or stereo headphones.

Practical guide / P150

Phantom power: requirement, supply and switch state

Keep microphone demand, receiver supply documentation and your observed switch state separate.

Practical guide / P151

Balanced mono is not stereo headphones

A TRS form can describe different circuits; preserve the intended channel layout.

Practical guide / P152

Interface to active monitors: one channel per speaker

Plan the left and right analog paths without counting alternative inputs twice.

Practical guide / P153

Audio interfaces: shared inputs are not extra channels

Record the physical channel behind a jack and the scope of a shared control.

Practical guide / P154

Direct boxes, source conflicts and audio patch reports

Keep conversion roles and unresolved specifications visible in a handoff.

NEW SOURCE-QUALIFIED AUDIO REFERENCE

Contacts are not channels.

Seven examples separate plug geometry, switched-jack construction and equipment port roles, with four new physical studies.

Read the illustrated field reference →

SOURCE-QUALIFIED OPTICAL REFERENCE

Same opening? Different question.

Seven examples separate optical interfaces, kits, shared photographs and panel cutouts. MT-RJ gains its first specimen study.

Read the optical role chart →