Audio-Technica AT-MX351 Phantom Power, Output Level LED Meter, Summary of Internal Controls

The preamplifier gain may be reduced further, allowing the SmartMixer to accept line-level sources. Changing the settings of the internal switches designated by “SW3,” “SW9,” “SW15” and “SW21” will cause an input reduction of 50 dB for channels 1, 2, 3 and 4 respectively.

Note that the appropriate internal switches can be used in combination for a total sensitivity reduction of up to 60 dB for each channel.

Output Level

The SmartMixer’s output is factory set at line level. Should mic-level output be desired, simply unplug the unit, remove the top cover and locate the switch on the circuit board marked “SW26” (Figs. 4 and 5, page 11). Changing the setting of this switch will cause a 50 dB reduction in output.

Phantom Power

Each of the SmartMixer’s inputs supplies +48V DC phantom power. Should it be required to disable the phantom power, simply unplug the unit, remove the top cover and locate the switches designated on the circuit board by “SW1,” “SW7,” “SW13” and “SW19” (Figs. 4 and 5, page 11). Changing the settings of these switches will disable phantom power on channels 1, 2, 3 and 4, respectively. Note that, although they do not require phantom power for operation, most balanced-output dynamic microphones can be used without disabling the SmartMixer’s phantom power.

Output Level LED Meter

The Output Level LED meter is factory set to indicate RMS output. Should peak output indication be desired, simply unplug the unit, remove the top cover and change the setting of the switch designated on the circuit board by “SW27” (Figs. 4 and 5, page 11). “Zero” (0) level is factory-calibrated at +4 dBm into 600 ohms.

Summary of Internal Controls

Function	Ch 1	Ch 2	Ch 3	Ch 4	Output
48V Phantom Power	SW1	SW7	SW13	SW19
10 dB Input Atten.	SW2	SW8	SW14	SW20
50 dB Mic/Line Atten.	SW3	SW9	SW15	SW21	SW26
Limiters (on/off)	SW4	SW10	SW16	SW22
“Off” Atten. Range	SW5	SW11	SW17	SW23
Preamp Output Gating	SW6	SW12	SW18	SW24
Limiter Thresholds	VR2	VR5	VR8	VR11
“Off” Atten. Adjustment	VR3	VR6	VR9	VR12
NOMA	--	--	--	--	SW25
Meter RMS/Peak	--	--	--	--	SW27

Figure 3. Summary of internal controls

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