Sound Devices MixPre-D - Manual (Page 6)

MixPre-D User Guide and Technical Information
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v1 .0 Features and specifications are subject to change . Visit www .sounddevices .com for the latest documentation .
Inputs
The MixPre-D features two transformer balanced analog inputs. Each input provides enough gain
to amplify a variety of signals from low-sensitivity ribbon and dynamic microphones, medium-level
wireless and condenser microphones, and “hot” line level signals.
The XLR inputs of the MixPre-D are transformer-balanced. The isolation characteristics of transform-
ers are superior to other balancing techniques and are ideal for the hostile and uncontrolled environ-
ments of field production. Transformers provide galvanic isolation from the driving source, meaning
there is no direct electrical connection. Signals are “transformed” magnetically. The input transform-
ers in the MixPre-D use premium magnetic core material to achieve high signal handling capability
(especially at low frequencies) while keeping distortion to a minimum. Because of their inherently
high common mode impedance, transformers are unrivaled by any other type of input for common-
mode noise rejection.
The inputs of the MixPre-D can be used as balanced or unbalanced. When unbalancing, ground
pin-3 to pin-1 of the XLR connector. There is no change in gain between unbalanced and balanced
connections into the MixPre-D.
Mic / Line Setting
Before plugging a source into an XLR input on the MixPre-D, set the Mic/Line and phan-
tom powering switch to the correct position:
Setting Input Source
48V Condenser microphones requiring phantom power
MIC Dynamic microphones, some ribbon microphones, devices outputting mic-level signal (for example,
wireless receivers) .
LINE Devices outputting line-level signal (outputs from other mixers, for example)
Phantom Power
Phantom powering is a fixed DC voltage at either 12 or 48 volts. This voltage is resistively applied
to pin-2 and pin-3 of an XLR connector relative to pin-1. There is no voltage difference between the
signal pins-2 and -3. Dynamic microphones will operate as normal when phantom power is applied
to them.
The MixPre-D can provide up to 10 mA to each input at 48 V, sufficient for the most power-hungry
condenser microphones. Many phantom powered microphones do not require 48 V and can be prop-
erly powered with 12 V. When acceptable, use 12 V phantom to extend the MixPre-D’s battery life.
The phantom voltage level can be set to either 12 V or 48 V and is applied across all inputs where
phantom power is selected.
To change the phantom voltage between 12 V and 48 V, hold down the Headphone Controller
and slide the Slate switch into the slate position. The 12 V Phantom LED on the left side panel
illuminates green when the phantom voltage is set to 12 V.
Input Gain Control
The amount of gain applied to an input is adjusted with the Input Gain Control. A fully
clockwise position results in no signal passing from the input to the output bus (muted).
Up to 66 dB of gain is available from for microphone inputs.