Description

The MIX 2:1™ Audio Combiner by Radial Engineering is a 2-Channel Mixer that passively sums two audio channels into one. This allows you to send the stereo signals from a Mixer, an audio interface, a portable mono playback device, or mix two signals together and balance their input levels to a single output.

Key Features

    
• Allows mixing two channels to a single mono output
    
• Individual level controls bypassable when not in use
    
• XLR and ¼" TRS inputs
    
• Completely passive, no power required

Combines two balanced mic or line signals

The inputs of MIX 2:1 feature XLR and ¼" TRS connectors, with ground-lift switches that eliminate noise and hum from ground loops, ensuring noise-free operation. You can activate and deactivate each input individually to monitor signals before summing them. A Trim control is provided for each input: by connecting two separate mono sources, such as the outputs of two microphone preamplifiers, you can attenuate them as needed to match their levels at the output. Both level controls can be completely bypassed, summing inputs 1 and 2 with the same settings, and preventing accidental or unwanted level changes. MIX 2:1 has a 180° switch on Input-2, to solve frequency cancellation problems due to out-of-phase inputs. Both signals are passively summed, then sent to a single XLR output that can be connected to an active speaker, or to the input of a console or recording interface. MIX 2:1 is made of robust 14-gauge steel, and features the classic I-beam structure that prevents stress on the circuit board, protecting it from solder joint failures, in addition to the book-end design that protects level controls and switches. A military-spec circuit board and high-quality components help maintain the integrity of the audio quality, without distortion or phase shifts, for completely transparent passively summed signals.

MIX 2:1™ - Practical Applications

Summing a stereo Aux to a mono input

Activate the level control bypass to sum both channels at unity gain to the mono input of a speaker or recording device.

Mixing the output of two microphone preamplifiers into a single track

Combine two tracks into a single input on your audio interface. Use the 180° phase inversion to ensure phase coherence between the two inputs.

Summing a stereo source into a single channel on a console

When available channels are scarce, MIX 2:1 allows you to sum a stereo output to mono, using only one channel on the console.

Mixing two dynamic microphones together into a single preamplifier

MIX 2:1 also works with microphone-level signals, which is useful when available input channels are low or you want to process two microphones using the same signal chain.

Overview

MIX 2:1 is a simple summing mixer that simplifies combining two audio signals. Whether you need to sum mic or line signals, or the outputs of two separate devices, MIX 2:1 allows you to do so without noise or sound coloration. XLR and ¼" TRS inputs are provided for easy connectivity, with a single XLR output to feed the destination device. Level controls are available for each input, which can be completely bypassed when summing the left and right outputs of a mixing console or recording interface. A 180° polarity inversion switch allows, for example, summing the signal from a microphone placed on the top of the snare drum and the signal from a microphone placed on the bottom and sending it to a single preamplifier, while ground-lift switches eliminate noise and hum caused by ground loops. Before making connections, ensure your audio system is off and all volume levels are turned down, to prevent connection transients from damaging your speakers or other sensitive components. MIX 2:1 is passive and requires no power. Each input has a ¼" TRS connector and an XLR connector to accept balanced Mic-level or Line-level signals. For best results, use only one of these connector types at a time on each channel. The XLR output of MIX 2:1 can be Mic-level or Line-level depending on the input sources and the amount of attenuation applied using the input Trim controls. Keep in mind that MIX 2:1 does not provide any gain to the input signal, so if you connect two microphones to the inputs, a microphone preamplifier will still be needed to boost the signal to line level.

Summing a stereo source to mono

With MIX 2:1, you can take a stereo signal from a mixing console or recording interface and quickly sum it to a mono signal to feed a single speaker input on a PA system. Press the ON buttons for both inputs to activate them. Then, activate the recessed switch on the right side of MIX 2:1 LEVEL CONTROL BYPASS - this will disable the input level controls for each channel, to ensure equal summing. MIX 2:1 will automatically compensate for the 6dB voltage gain that occurs when two in-phase signals are summed together, so as not to distort the inputs of the destination device. To attenuate levels, simply deactivate the LEVEL CONTROL BYPASS and adjust each level control until desired results are obtained.

Summing two separate sources

MIX 2:1 is also useful for summing audio signals from two different devices, such as a guitar microphone and a passive DI, or microphones placed above and below a snare drum. When summing two separate sources, start with the input level controls fully clockwise (max) and use the ON switches to listen to each channel individually. If one signal is significantly louder than the other, use that channel's level control to achieve the desired balance between the two signals.

Using the 180° switch

MIX 2:1 includes a 180° switch that flips the audio polarity on INPUT-2 - sometimes called "phase inversion". When two audio signals have similar content but inverted polarity, summing the signals together can cause certain frequencies to be canceled or amplified, creating a filtered or unnatural sounding result. The 180° switch can be a quick way to reverse this effect and bring the signals back into alignment with each other, resulting in a fuller, more balanced sound.

Using the Ground-lift

When connecting two or more powered devices, noise and hum caused by ground loops may occur. MIX 2:1 has Ground-lift switches on both inputs that disconnect pin-1 on the input connectors, breaking the electrical path to ground and removing the noise. If noise or hum occurs when using MIX 2:1, simply use these switches to eliminate the problem.

MIX 2:1 Technical Specifications

    
• Audio circuit type: passive mixer
    
• Frequency response: 20Hz to 20kHz
    
• Dynamic range: >133 dB
    
• Total harmonic distortion: >0.005% @ 0dBu
    
• Intermodulation distortion: >0.002% at 0dBu
    
• Phase deviation: 0° at 20 Hz, 0° at 1 kHz, +2° at 10 kHz
    
• Input impedance: 8 kΩ
    
• Output impedance: 1 kΩ
    
• Common-mode rejection ratio: >80 dB
    
• Noise level: -113 dBu
    
• Maximum input: >+20dBu

Features

    
• 180° polarity inversion, Ground lift, Level control
    
• Input connectors: 1/4", XLR
    
• Output connectors: XLR

General

    
• Construction: 14-gauge steel chassis and outer shell
    
• Dimensions (L x W x D): 5" x 3.25" x 1.85" (12.7 x 8.3 x 4.7 cm)
    
• Weight: 0.67 kg (1.48 lbs)
    
• Shipping dimensions (L x W x D): 15.9 x 10.5 x 7.6 cm (6.25 x 4.12 x 3 inches)
    
• Shipping weight: 0.8 kg (1.77 lbs)
    
• Power: passive, no power required
    
• Conditions: for use only in dry locations between 5°C and 40°C