Echo Gina3G Owner's Manual

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Appendix G: An Introduction to Digital Recording76Appendix G: An Introduction to Digital RecordingBalanced signals connect with either XLR connectors or TRS (tip, ring, sleeve)connectors. Your Echo product uses XLR connectors for microphones and TRSconnectors for connecting balanced (or unbalanced) line level signals.The three sections of a TRS connector are used to transmit the three components ofa balanced signal (T = plus, R = minus, S = ground).Dynamic RangeDynamic range represents the difference between the maximum signal that can berecorded and the “noise floor”, or level of noise with no signal present. A systemwith a high dynamic range will be quieter than one with a lower dynamic range.Dynamic range is a very important specification, and your echo product usesconverters that have very high dynamic range.Theoretically, a 24-bit system has a dynamic range of 144dB and a 16-bit systemhas a dynamic range of 96dB. Two questions immediately come to mind:1) Why does my Echo product only have a dynamic range of 110 to 114dB?2) For mastering 16-bit CDs with a dynamic range of 96dB, isn’t anythingmore than 96dB just overkill?First, today’s analog-to-digital converters typically produce a full-scale inputvoltage with an input of +7dBu. If they were to have 144dB of dynamic range,they would have to be capable of resolving signals as small as –137dBu (7dBu –144dBu) or approximately 10 nano-volts. That’s 10 one-billionths of a volt!Transistors and resistors produce noise in this range just by having electronsmoving around due to heat. Even if the converters could be perfectly designed toread these levels, the low noise requirements of the surrounding circuitry such aspower supplies and amplifiers would be so stringent that they would either beimpossible or too expensive to build.