Radial MIX 2:1 Passive Two-Channel Summing Mixer & Combiner, XLR/TRS, Level Trim

Radial MIX 2:1: Two Signals, One Clean Mono Output

The Radial MIX 2:1 is a passive two-channel summing mixer that combines two balanced mic- or line-level signals into a single mono output, with an independent level trim on each input. Because it uses a completely transformerless, resistive summing circuit with no ICs in the path, it stays utterly transparent: what you put in is what you get out. When you are one channel short at exactly the wrong moment, the MIX 2:1 quietly solves the problem so the session or the show never stops.

How Passive Summing Keeps It Simple and Quiet

Summing two signals by simply tying them together causes them to load each other down and lose level, but the MIX 2:1 does it properly with a passive resistive network that keeps the sources isolated and balanced. It also automatically compensates for the 6 dB of gain that naturally occurs when two in-phase signals are combined, so the mono output does not jump in level. With no transformers, no chips, and no power supply in the path, there is nothing to add coloration or noise, and the result is a dynamic range beyond 133 dB with distortion below 0.005 percent.

Level Trims, Bypass, and Polarity Control

Each input has its own trim control, so when you are combining two separate mono sources such as the outputs of two preamps you can attenuate each one to match their levels at the output. When you are summing a stereo pair that is already balanced, a level-control bypass switch takes the trims out of the circuit entirely for a unity-gain, straight-wire path. A 180-degree polarity reverse on one input lets you correct phase between the two signals so they reinforce rather than cancel, and it stays active even with the level bypass engaged.

Mic-Level and Line-Level on the Same Box

The MIX 2:1 handles both mic- and line-level signals, accepting up to more than +20 dBu, so it works equally well summing the stereo outputs of a console or interface and combining two dynamic microphones on a single amplifier. Both 1/4-inch TRS and XLR inputs are provided on each channel, with ground-lift switches to break ground loops. Note that it is not a microphone preamp and its XLR output has blocking capacitors, so when summing microphones you disengage phantom power and feed the mono output into a preamp or console mic input.

Stereo to Mono, Two Mics to One Track

Sum the stereo aux or line outputs of a console down to the mono input of a powered speaker at unity gain by engaging the level bypass. Combine the outputs of two mic preamps into a single track on your interface when you are low on inputs, using the polarity flip to keep them phase-coherent. Or blend two dynamic microphones on one guitar cabinet into a single preamp channel, capturing both mics through one signal chain when channels are scarce.

For Engineers Short on Channels

The MIX 2:1 is the small box that lives in a gig bag, a studio drawer, or an install rack for the day you need to fold two signals into one. Front-of-house and monitor engineers, recording engineers, broadcast operators, and AV integrators all reach for it when input channels run out or a stereo source has to land on a mono system. Simple, transparent, and passive, it does one job perfectly and asks for nothing in return.