Studio Technologies 742A Audio Mixer

The Model 742A Audio Mixer is expressly designed for use in electronic-news-gathering (ENG) vehicles and small production truck applications. Many other fixed and mobile audio production, on-air, and utility applications can also be supported. Model 742A features include four mic/line inputs with +48 volt phantom power, four line inputs, two output buses, LED level metering, flexible monitoring, and AC and DC powering. The Model 742A was specifically designed as a dual-channel audio mixer, rather than as a typical stereo device. This approach makes it excellent for "dual-path" on-air applications. As a utility mixer the Model 742A can create two independent monaural signals, excellent for general signal monitoring, talent cueing, or intercom support uses.

Key Features

• Four mic/line and four line-only inputs
• Setup oscillator with dedicated output
• Studio-quality compressors
• Internal power supply
• Flexible monitor section
• 10-segment LED meters
• AC mains and DC powering
• +48 volt phantom power
• All operator controls on front panel
• Single rack-space mounting

Technical Specifications

Frequency Response
20 Hz to 20 kHz, -0.5 dB, mic/line in to main outs
Distortion (THD+N)
0.03 %, measured at 1 kHz, +4 dBu, mic/line in to main outs
S/N Ratio
74 dB, referenced to +4 dBu, mic/line in to main outs, 22 Hz to 22 kHz
Mic/Line Inputs
4
Input Sensitivity
Switch selectable for microphone or line-level signals; 44 dB line input "pad" implemented using sealed bifurcated contact telecom relays
Phantom Power
48 Vdc, nominal, meets IEC 61938 P48 standard
Operating Level Range
Mic input position: -76 to -8 dBu; line position: -32 to +28 dBu. Range specified to give +4 dBu on main outs, master level controls set to unity gain.
Type
Electronically balanced
Impedance
Mic position 1.3 k ohms, line position 15 k ohms
Common Mode Rejection Ratio
74 dB @ 60 Hz, 73 dB @ 40 kHz (typical), mic position, ref +4 dBu on main outs
Status LED
Dual-color, displays signal present and peak
Line Inputs
4
Operating Level Range
-14 to +28 dBu. Range specified to give +4 dBu on main outs, master level controls set to unity gain.
Type
Electronically balanced
Impedance
24 k ohms, nominal
Common Mode Rejection Ratio
85 dB @ 60 Hz, 85 dB @ 40 kHz (typical), ref +4 dBu on main outs
Status LED
Dual-color, displays signal present and peak
Compressors
2
Function
Controls dynamic range of output buses 1 and 2
Type
Single-knee, VCA-controlled
Slope
5:1
Threshold
Configurable, choices are: 6 dB over nominal (+10 dBu on main output, factory default); 2 dB over nominal (+6 dBu on main out); disabled
Attack Time
2 ms
Release Time
100 ms
Status LEDs
2, compressor active
Main Outputs
2
Type
Electronically balanced, capacitor-coupled, intended to drive balanced or unbalanced loads of 600 ohms or greater
Source Impedance
50 ohms, nominal
Nominal Level
+4 dBu
Maximum Level
+26 dBu into 10 k ohms, +25 dBu into 600 ohms
Monitor Outputs
2
Signal Sources
Output buses 1 and 2
Type
Electronically balanced, capacitor-coupled, intended to drive balanced or unbalanced loads of 600 ohms or greater
Source Impedance
50 ohms, nominal
Nominal Level
Configurable, choice are: +6 dBu, with monitor level control @ 100%, mode configured for POST level control; -10 dBu when configured for PRE -10; +4 dBu when configured for PRE +4
Maximum Level
+26 dBu into 10 k ohms, +25 dBu into 600 ohms
Headphone Output
1
Signal Sources
Output buses 1 and 2 ("post" monitor level controls)
Type
Stereo, configured to drive headphones through 100 ohm series resistors
Compatibility
Intended for connection to headphones with impedance of 100 ohms or greater
Maximum Voltage
8 Vpp, 100 ohm load
Reference Tone
Frequency and Wave Form
400 Hz nominal, sine wave (technician can revise to 1 kHz)
Direct Output Level
+4 dBu, nominal, adjustable over -1/+3 dB range
Direct Output Type
Electronically balanced, capacitor-coupled, intended to drive balanced or unbalanced loads of 600 ohms or greater
Direct Output Source Impedance
100 ohms, nominal
Meters
2
Function
Displays level of output buses 1 and 2
Type
10-segment LED, modified VU ballistics
Connectors
Mic/Line and Line Inputs
3-pin female XLR
Main Outputs
3-pin male XLR
Reference Tone Direct Output, Monitor Outputs, Headphone Output: 1/4-inch 3-conductor phone jack
AC Mains Input
3-blade, IEC 320 C14-compatible (mates with IEC 320 C13)
DC Input
4-pin male XLR
AC Mains Requirement
100-240 volts (-15/+10%), 50/60 Hz, 15 W maximum
DC Input
10-18 volts DC, 1.0 A maximum @ 12 volts; 1.1 A maximum @ 10 volts; current draw when AC present is less than 100 uA
Dimensions (Overall)
19.0 inches wide (48.3 cm) x 1.72 inches high (8.9 cm) x 9.2 inches deep (23.4 cm)
Mounting
One space (1U) in a standard 19-inch rack
Weight
4.3 pounds (1.9 kg)