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Chapter 7 ( thompson ) Lines and interconnections

Chapter 7 ( thompson ) Lines and interconnections. How do we send signal? . We need “Transducers” Analog vs. Digital Connections What’s the difference? What should we consider when transferring data? The ________distance from one point to the next is usually the best.

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Chapter 7 ( thompson ) Lines and interconnections

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  1. Chapter 7 (thompson)Lines and interconnections

  2. How do we send signal? • We need “Transducers” • Analog vs. Digital Connections • What’s the difference? What should we consider when transferring data? • The ________distance from one point to the next is usually the best. • Meaning: Length of cable, conversion, processing through gear

  3. TRANSFORMERS

  4. TRANSFORMERS • Transforms electrical energy from one circuit to another • A transformer has COILS which create a varying magnetic flux. The windings determine the “RATIO” • Transformers are useful in audio because they can change the impedance of a signal. i.e. A microphone going to a mixer

  5. More on TURNS RATIO • There is a PRIMARY and SECONDARY wiring in every transformer • A transformer can step UP or DOWN depending on the ratio. • Voltage and current is directly related to the ratio Thompson p. 156-157

  6. Unbalanced Lines • What are some unbalanced connections? • What’s the biggest issue with them? • Multiple pieces of gear connected together can cause “Earth Loops” or “ground loop hum” at 50Hz

  7. Balanced Lines • What kinds of connections are balanced? • They reject interference better • Known as CMR or “Common Mode Rejection” • Think of it as one + and one – canceling each other out with transformers on each end. • Accepts “Differential” signal but rejects “Common Mode”

  8. XLR Review • Hot (+) Cold (-) and Ground • Pin 1 = Ground (Screen) • Pin 2 = + Hot • Pin 3 = - Cold • Balanced to unbalanced can still avoid a “Earth (Ground) loop” but cannot reject interference. • TRS has the same connections (You can convert between the two) Thompson p. 164

  9. CABLES • CONDUCTOR: Sends signal • INSULATOR: Separates signals, prevents crosstalk • SHIELD: Eliminates noise & Interference

  10. Multicore Cables (ex. Snake) • Ability to send multiple analog inputs and outputs over the same cable • Twisted cables help reject interference • Try to avoid “Crosstalk”: When signals interfere with each other • How can digital cables be advantageous in situations where multiple channels are needed in one connector?

  11. DI Boxes • Direct Injection Boxes • Converts Unbalanced inputs to a Balanced output • Another way to look at it: Converts hi-impedance to low-impedance • Can be active or passive • See figure 12.14 • Generally used on instrument cables

  12. Splitter Boxes • Splits one signal into two • Required to maintain a suitable impedance for the microphone • There is ONE primary winding and TWO secondary windings • This creates a ratio that loses 3dB of signal • BUT it also halves the impedance, so there is not difference unless the impedance gets too low.

  13. PATCHBAYS • Also known as “Jackfields” • Easy way to ROUTE equipment without having to access the specific piece • Usually 24 sockets in a row • “TT” Tiny-Telephone connections • Balanced, so they maintain signal integrity • They usually are NORMALLED to a certain piece of gear

  14. 4 Connection Types • Top row is OUTPUT, bottom row is INPUTS • Open: Never makes a connection between the top and bottom unless plugged in • Half-Normalled: Keeps the signal but allows you to plug into the OUTPUT • Fully-Normalled: Any connection will disturb the normalled connection. • http://www.whirlwindusa.com/pre01.html

  15. DISTRIBUTION AMPLIFIERS • Allows for distribution of one input to a number of outputs • They have independent level control and isolation • Every output is not affected by connections made to others • This differs from a SPLITTER in that sense… it is also strictly for amplification.

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