Chapter 10

FX Loops

An FX loop is a powerful bypass system found at the back of amps with this feature. Some amps have an FX loop option, and others do not. An FX loop in the amp allows you to route sound, bypassing the pre-amp section and going directly to the power amp section. Why would you bypass the pre-amp, the initial gain stage, to get a signal amplified by the power tube section alone?

Some pedals work better this way, particularly time-based effects (delay and reverb). If you do not use an FX loop but put the time-based pedals at the end of a direct chain going into the amp’s front, the time-based effects will sound less articulated than the FX loop because of pre-amp processing. The more processing, such as distortion, the less articulated it will be. However, this is not always a bad thing. For example, there are loads of Marshall Plexi amps with no FX loop throughout the decades with an Echoplex delay going in the front. The Echoplex had a pre-amp that colored the tone and sounded great, as countless hard rock Plexi players in the 70s and 80s demonstrated.

The FX pathway allows you to segregate your pedals into time-based (and EQ) and everything else. The FX loop bypasses pre-amp gain staging like another input.

Some amplification with gain is needed to hear any pedal, but bypassing the pre-amp tubes for the power tubes will be sufficient. This is because the direct input sound going through the pre-amp stage will be processed through the FX pedals before the processed sound goes to the power tubes.

You create a loop for the time-based pedal chain separate from your direct pedal chain that will go into the front. The time-based chain will loop to the amp and back to the pedals again. There is an FX in and an FX out. For example, the delay pedal will go to the reverb pedal. Go to the amp FX loop in from the reverb pedal line out. From the amp FX loop out, we go to the input of the delay pedal. It’s a true loop.

Your guitar cable and your other pedals do not interface with the loop. The pedals might all be on the same pedalboard in a row, looking like it is direct, but there is a loop for the FX. The result is four cables (not to be confused with the ‘four-cable method’ for modelers) from the pedalboard. The input into the pedal from the guitar is one cable. The cable to the amp input is another. The FX loop involved two cables for the input and output of the FX. So that is four main cables; the remainder are patch cables between pedals and power cables.

Some FX loops can get a little complicated, depending on the amp. Some need to be switched on from the amp and maybe even stompable in a footswitch, and in some cases, you need the footswitch to get it working in the first place. So make sure you find out how an FX loop works on the amp you are getting. Don’t just expect them to behave the same as another FX loop, even in the line of amps, but in different models. For example, the Marshall Studio amps have a switchable (on/off) FX loop at the back, but the Studio Jubilee does not have that at the back. The EVH 5150 50W 6L6 fx loop, needs a footswitch to be activated.

An additional kill switch pedal is needed in the FX chain to bypass the effects of FX loops that are always on. So that becomes your FX loop on-and-off switch.

Another advanced piece of gear for dealing with complex rigs is something called an effects switcher. They are footswitches with rows of stomps that are programmable to manage your pedalboard and rig. At first, they may look like a pedal for modeling effects, but this isn’t the case. They usually have no onboard effects. They manage the effects you already have.

Boss MS-3 multi effects switcher. Noticed all the inputs and outputs out the top.