Series vs. Parallel Effects Loops – What’s the difference and how are they used?

When you decide to add effects to your guitar sound start by asking yourself “Do I want to change my sound? Or do I want to add something to my sound?”

Think about those old pedals that go between your guitar and the input of your amplifier. The signal goes from one pedal to the next in series. There is only one signal path from the guitar, through each of the pedals and on to the amp. On the other hand, when your engineer turns up the delay send on your guitar channel at the mixer, part of your sound is sent to the delay processor and then returned to the mixer but the main signal still runs dry [unaffected] through your channel, so you hear a mix of the two in the main speakers. Parallel systems allow you to blend your sound with the effect.

Start by asking yourself “Do I want to change the fundamental character of the sound with this unit?” If so you will want to use this effect in series, and generally prior to any parallel effects you plan to use. Some examples that tend to work best this way are distortion and wah, where you want your guitar to sound like the effect. With series effects it is important to consider which order you put them in because each subsequent effect is colored by the ones before it in the signal chain. Any series effects that you want to come after your amplifier preamp will go in the series effects loop. 

Series loop setup:

It is very important to match the signal levels of your series effects to the loop you are using especially when it can be bypassed. On simpler pedals, input, output or mix volumes may not be available, so you will have to work with what is available. Sometimes you can include other pedals with these controls to help. For the ideal situation this is the process: Start by adjusting the effect input level for a strong clean signal, and then adjust the output level so that it doesn’t change your volume when you bypass the loop. Then if it has a mix level, you can adjust the mix to your liking. The mix level makes it a parallel effect, but because the mix is internal to your unit and it is placed in the series loop of your amp, you are still always sending the original signal through the effect unit. The electronics of the pedal will still have some effect not present when it is not plugged in to the series effects loop.

Using the parallel loop:

If you want to blend the effect along with your main guitar signal, then you’ll want to use a parallel loop. Any kind of processing will push your guitar farther back in the mix and reduce how much clarity and presence it will have out front. By running your effects in parallel you can keep your main guitar sound dry [unprocessed] and up front. Spatial effects like delay, reverb and chorus are intended to be parallel in normal use (although some of us are abnormal users). In fact, a chorus, without original signal, would simply be a very short odd delay, and the delay effect would just be the same sound but delayed. As mentioned some units allow you to program the mix inside of it. And in a pinch you can accomplish parallel effects in a series loop by setting the mix inside your processor, but the tone of your main guitar signal will be affected by the quality of your unit’s dry or original single circuitry.

Listen to some of your favorite guitar sounds and see if you can recognize which effects are in series and which ones are parallel. Then try some effects concepts of your own. Be sure to match the signal levels to avoid signal degradation (wrecking your tone) and become familiar with how the different effects interact when combined in various ways. Pedals are usually intended to go between the guitar and amp, and rack units are usually designed to be used in your effects loop. Carvin Audio’s V3 amplifier allows you to use both series and parallel connections to your effects.

V3 amp features series and parallel connections

Be creative. Think of effects as special colors and tools that you can use to make your music uniquely personal. There is no “right” or “wrong” way to process your sound, only those that become your favorites and those that are soon forgotten. 

Also in Guitar / Bass Amplifier Info & Education