Lexicon Converter Termination and Grounding via Internal Jumpers, Signal Type Attenuator DBu DBV

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20/20 AD User GuideUsing the 20-/20 AD

The 20/20 AD has four analog inputs: CH1, CH2, CH3 and CH4. In two-channel Analog Inputs mode, only CH1 and CH2 are used, and the dynamic range of the unit is

extended. If you have two stereo pairs, one of which is used more often than the other, the most often used pair should be assigned to CH1 and CH2, and the other pair to CH3 and CH4. This allows you to take advantage of the extended dynamic range of two-channel mode when using only a single stereo pair.

When digitizing stereo pairs, the left channel of each pair should be sent to CH1 and CH3; the right to CH2 and CH4.

The 20/20 AD accepts balanced or unbalanced signals with the following peak input levels:

Signal Type

Attenuator

dBu

dBV

 

 

 

 

balanced

OFF

+2 to +22

0 to +20

 

balanced

ON

+8 to +28

+6 to +26

unbalanced

OFF*

-4 to +16

-6 to +14

 

 

 

 

 

*Unbalanced signals cannot be correctly attenuated with the front panel ATTEN button. Input levels of unbalanced signals must be lowered before entering the 20/20 AD.

The analog XLR connectors should be wired as follows:

Signal Type

Pin 1

Pin 2

Pin3

 

 

 

 

balanced

screen

positive

return

 

(shield)

polarity

 

unbalanced

screen and

positive

open or

 

return

polarity

return

 

 

 

 

In a typical studio environment, each piece of equipment is connected to a “star ground” through the safety ground on the AC connector, or through a ground strap tied to the chassis. In these cases, connecting the shield of the audio cable(s) to pin 1 at both ends of the cable will cause the 20/20 AD to be grounded to the audio source through two paths: the shield of the audio cable and the safety ground or ground strap. This will result in a “ground loop” which manifests itself as hum at the power line frequency.

A common solution to this problem is to connect the cable shields only at the source end, and to leave pin 1 of the 20/20 AD end floating. If this is not practical, you can open the ground jumpers (W1, W9, W11 and W13) on the 20/20 AD’s analog inputs.

Termination and Grounding via Internal Jumpers

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Contents 20/20 AD Precautions Electrostatic Discharge ESD Precautions Safety SummaryContents AES/EBU Interface Professional IntroductionPower Mounting Controls and ConnectorsConverter 20/20 AD Front Panel ControlsCompressor Level MetersDisplay LinkAlternate Modes Synchronization Output FormattingTo activate Alternate modes Press and hold Then press one of theseBAL/UNBAL 20/20 AD Rear Panel ConnectorsAudio Connections ConnectorsXLR Pinout AES/EBU CablesPdif Signal Type Pin Pin3 Signal Type Attenuator DBu DBVTermination and Grounding via Internal Jumpers Word Clock These instructions are for use by qualified personnel onlyAnalog Jumpers Balanced Unbalanced Input Signals PK Hold Front panel AdjustmentsAtten ChanAES Sync Word Clock Synchronization and Sample RateInternal and External modes StatesPsychoacoustically Optimized Noise Shaping Pons About Dither00k 10.0k 12.0k 14.0k 16.0k 18.0k Dynamic Range Compression Automatic Offset Removal Compressor ModesInput Gain Threshold Release Compressor Knob ValuesTransfer Functions Non-linearUsing the 20/20 AD Lexicon Link Digital Sinewave Generator Realigning Two DAT RecordingsGain Operating the 20/20 AD in the Digital Mode Cmrr SpecificationsDefinition of Terms