Connectors and Cables

1. Connectors and Cables Types of connectors and cables Wiring standards Soldering principles Cable testing

2. Connectors Microphones • Professional quality will always use either XLR or RTS • XLR is the most common • Locking connector for greater reliability 3 pin XLR

3. Connectors Microphones • Pin out • Term which defines which conductors land on which pins • There are standards for different devices • The standards change in different parts of the world Pin 1 – Ground Pin 2 – Signal Hot Pin 3 – Signal Return

4. Connectors • Ring – Tip – Sleeve • Used for balanced mic signals • More often used unbalanced for multiple channel connections Balanced Pin 1 – Shield Pin 2 – Signal Hot (+) Pin 3 – Signal Return (-) Unbalanced Pin 1 – Signal Return (-) Pin 2 – Signal 1 Hot (+) Pin 3 – Signal 2 Hot (+)

5. Connectors • RCA plugs • Sometimes called phono plug • Not to be confused with ¼” phone plugs • Always unbalanced Pin 1 – Signal Hot (+) Pin 2 – Signal Return (-)

6. Balanced vs. Unbalanced • Unbalanced – 2 conductors. Hot and return • Often the return is a screen or braid around an inner conductor • Low levels of noise resistance • Good for short cable runs at line level or speaker level • Balanced – 3 conductors. Hot, return and shield • Shield is a braid or metallic foil around two inner conductors • Sometimes inner conductors are a “twisted pair” • Shield is connected to ground and bleeds off any induced current • High levels of noise resistance • Good for long cable runs. Typically at microphone level.

7. Cables • Wire • One individual conductor • Cable • Two or more conductors combined together in a flexible jacket

8. Cables • Cables in theatrical applications receive very rough treatment • Stepped on, genie lifts and forklifts roll over, twisting and pulling… • Even the best audio equipment in the world will not work with damaged cables! • Coiling • The over the forearm method is about the worst thing you can do to any cable • The wires inside the cable have a natural “lay”. • They will coil nicely if they are allowed to • Forcing the wires to bend will weaken and eventually break the wire causing shorts or intermittent connections.

9. Cables • Cables should always be run “cleanly” • Use the shortest lengths you can. • Avoid large coils when possible • This allows for an easy concentration of induced noise • Never bend cables over sharp edges or right angles • Dropping a cable over and I-beam for example • Always tie up or tape down under carpets or mats or use industrial cable covers. • Avoid using “gaff tape” directly on cable jackets. • Tape will often leave behind a residue of stickiness • If two adhesive sides come together it is very difficult to remove.

10. Cables • Snakes • A cable with multiple pairs of conductors, each with it’s own screen protected by an overall insulating jacket “Tails” “Break out” box

11. Cables • Loudspeaker cable • Carries much higher electrical power than mic or line level cables • Need to be much larger gauge with heavy duty connectors on each end or bare wires • Wire has it’s own internal resistance which will degrade the signal before it reaches the speaker • 12 gauge 0.159 Ω / 100 feet • 16 gauge 0.402 Ω / 100 feet • 24 gauge 2.567 Ω / 100 feet

12. Cable Testing • Tools of the trade • Multi-meter • Device which can measure • AC & DC voltage • Remember AC voltage changes with time • Most meters take and average, NOT RMS value • RMS = root-mean-square, which is a more accurate means of measuring voltage • AC & DC current • Resistance • Continuity • Some meters will measure other things as well • Battery checker • Diode checker

13. Cable Testing • Oscilloscope • A device which draws a graph of a changing electrical signal in real-time • Allows you to view exactly what the sine wave looks like • Usually a large bench test piece of equipment not usually used in simple sound equipment testing • Line tracer • “Fox and Hound” • The “fox” puts an AC signal on a wire and the “hound” picks it up at the other end • The “hound” looks for the changing magnetic field that the “fox” produces • Can be measured through insulation

14. Soldering • Here's a summary of how to make the perfect solder joint. • All parts must be clean and free from dirt and grease. • Try to secure the work firmly. • "Tin" the iron tip with a small amount of solder. Do this immediately, with new tips being used for the first time. • Clean the tip of the hot soldering iron on a damp sponge. • Many people then add a tiny amount of fresh solder to the cleansed tip. • Heat all parts of the joint with the iron for under a second or so. • Continue heating, then apply sufficient solder only, to form an adequate joint. • Remove and return the iron safely to its stand. • It only takes two or three seconds at most, to solder the average joint. • Do not move parts until the solder has cooled. • Troubleshooting Guide • Solder won't "take" - grease or dirt present – de-solder and clean up the parts. • Joint is crystalline or grainy-looking - has been moved before being allowed to cool, or joint was not heated adequately - too small an iron/ too large a joint. • Solder joint forms a "spike" - probably overheated, burning away the flux.

15. For Next Class • Read • Mixing Desks, Kai’s Sound Handbook • P. 66-82, Leonard • Within this reading section, there is some out of date discussion of specific makes and models of equipment. This specific material will NOT be on any test.