An effects loop is a pair of connections allowing a musician (typically a guitarist) to place effects pedals or signal processors in more than one place in their signal chain. You may wish to put distortion and compression effects between your guitar and your amplifier's main input, and time-based effects like delay and reverb in your amplifier's effects loop, which is inserted between the preamp and power amp, giving it a distinct tone. The SKB PS-25 is a pedal board and hard shell case designed with this type of setup in mind. The patch bay at the top of the board contains two sets of inputs and outputs, and corresponding connections on the top outside edge for connection to your amplifier. Understanding how these connections are used will give you great flexibility in setting up your pedal board signal chain.
Connect you guitar's output jack to the "Loop 1" input of your pedal board, located on the top outside edge of the board's patch bay.
Connect the "Loop 1 Send" jack to the effects pedal chain you wish to place before the amplifier. Connect the output of the last pedal in this chain to the "Loop 1 Return" jack. The best effects to use in the chain before your amplifier's input are typically compression and distortion type effects.
Connect the "Loop 2 Send" jack to the input of the pedal chain you wish to place in your amplifier's effects loop. Connect the output of the last pedal in this chain to the "Loop 2 Return" jack of your pedal board. The most common types of effects used in an amplifier's effects loop are time-based effects such as delay, reverb and chorus pedals.
Connect your amplifier's effects loop send jack to the "Loop 2 Input" jack of your pedal board, and the "Loop 2 Output" jack to your amplifier's effects loop return jack. You now have two sets of signal flow running through one pedal board.
There is no official right or wrong place to put any effects pedal in your signal path. the examples given are the most common, but feel free to experiment with different pedals in different orders. You may find that an unconventional setup sounds the best to you, and helps you achieve your desired tone.
David Medairos is a freelance writer and musician. With more than 10 years of experience in various fields, he has amassed a general knowledge of most technical and mechanical subjects, computer science and audio engineering, as well as R&D, customer service and marketing. He has written for "Connections Magazine," and is a frequent blogger on several consumer tech sites.