The cabling that we use to connect devices (instruments, mics, media devices) to the system is going to have a minimum of two conductors. An unbalanced cable has one "hot" conductor and one grounded conductor (a shield return). A balanced cable has two "hot" conductors that carry equal but opposite signals and that "twisted pair" as it is often called is surrounded by a grounded shield. In professional audio systems, unbalanced cables are essential because they can run for hundreds of feet without incurring any substantial loss or noise, whereas unbalanced cables can get noisy and flaky after about a 20-30 foot run. However, we still have to deal with unbalanced lines too.
All of your XLR cables are balanced. Your guitar cables are unbalanced. The DI boxes provide an unbalanced input and they convert the incoming signal (TS) to balanced output (XLR).
Now, what do I mean by "TS"? This is a term that applies to those 1/4 inch connectors that you see on the instrument cables. A "TS" plug means "tip/sleeve". The sleeve is grounded, the tip is hot. A similar-looking plug has an additional conductor called the "ring". It looks like a stereo headset plug, but for the purpose of interconnecting devices, it is a balanced cable and it is called a TRS (tip/ring/sleeve). TRS has 3 distinct conductive surfaces, separated by thin rings of plastic, whereas the TS has only two. A stereo headset uses the TRS plug in its unbalanced form: the tip for one channel, the ring for the other and the sleeve as the shield return. A balanced cable uses the tip for one "hot", the ring for the other "hot" and the sleeve for the shield.
The plugs at the patch bay are TRS but they use a slightly different type of plug that has its roots in military and telephone applications. For practical purposes, it's a TRS. Never uses an unbalanced TS cable at the patch bay as it will result in hum and noise.
Jim K.
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