One of my most popular articles has been The Mono Summing Cable that No One Makes. I’ve been contacted by more readers regarding that article than probably any other that I’ve written. That article details why it’s a bad idea to use a regular Y-cable or TRS-to-TS cable to sum two (usually stereo left & right) line-level signals to mono by simply shorting the outputs together. It’s ok to use such a cable for SPLITTING a signal, but not for COMBINING or SUMMING two signals. That being said, it can work ok on some devices, but on others it can cause distortion, weird phasing artifacts, and possibly even damage the outputs of your gear. However, combining the outputs of two dynamic microphones is a different story, and in some applications it’s ok to do so with a regular XLR Y-cable, as we will soon see. (more…)

One of my most popular blog posts has been The Stereo to Mono Summing Cable that No One Makes. I get contacted pretty much on a weekly basis from someone who wants to buy or build that cable to connect their iPod, phone, laptop, etc. to their PA system. I decided to take the concept a step further and build a balanced, line-level stereo to mono summing box. Just like the mono-summing cable, it appears that there aren’t any readily-available, off-the-shelf products that do exactly what this box does. There are some mic combiners (e.g., Galaxy Audio’s JIB/C) that are made for connecting two microphones to a single input, but those use much lower-value resistors, making them unsuitable for line-level signals (I even contacted Galaxy about the JIB/C, and that’s what they told me). (more…)