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Articles: Parallel Effects

Whether in the studio or on stage, as recordists or musicians we all run into a situation eventually where one sound doesn't do the job. It might be a distorted electric guitar sound which doesn't have the clarity needed. On the other hand, the clean electric guitar sound might not have the punch you want. Wouldn't it be nice to have a combination of both?

So you take two amps, set one to distort and the other to a clean sound, then mic up and mix the two. Problem solved! This is the simplest example of using two effects in parallel (remember, an electric guitar amp is an important part of the electric guitar sound and, as such, is an effect). The analogue for a bassist is when, in the studio, the engineer uses a DI box to get a direct sound while also driving a bass amp and miking it up.

Series Effects
seriesfx.gif (2725 bytes)This is the usual manner of connecting effects - from the output of one into the input of the next, into the next, etc.. This is called series connection. Series connection is a perfectly valid way of doing things, and has been used to create some of the effects sounds we all know and love. However, if you only use series connection of your effects, you are limiting yourself. There is a whole other world available to you in parallel effects.

Parallel Effects
When running effects in parallel, we drive the inputs of two or more effects with the same source signal (such as the electric guitar or bass in the example) by splitting it into two or more 'branches'. Then the outputs of the two can be recombined using a mixer. This gives a range of sound combinations not available with series.

Of course, it need not stop there. Now it is possible to treat each branch as an effect chain. Each can also be EQ'ed differently at the mixer and panned to different positions in the stereo soundstage for a really large, spacious sound.

For recording, you can record each on two separate tracks on a recorder. This allows you to decide how to mix things later in the mixing process, when you have a better idea of what will work best in the song. For a guitar signal, another option is not to mix them back together, but to drive two different amplifiers.

Parallel Effects

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Splitting the Signal
In a perfect world, you would be able to use a simple splitter cable to split the signal into two branches. Unfortunately, the inputs of many effects do not play nicely with others, and one may 'snatch' all the signal for itself, leaving nothing for the other effect. There are a few ways of getting around this.

  • Splitting buffers or 'Spluffers' - these are specially designed for parallel effects usage. They consist of two identical buffer preamplifiers in one box which have separate outputs but share the same input. Unfortunately they are not very common and must usually be built to order.
  • DI boxes - using two identical DI boxes and a splitter cable is essentially the same as a spluffer, but is more easily available.
  • Stereo Mixers - using a stereo mixer is another option. Pan your input to the centre and the left and right outputs are identical buffered signals. You could also use spare auxiliary channels or output busses on your main mixer if you have them to spare.
  • Stereo effects - many effects such as delay, chorus and autopanners are by their nature stereo and have separate outputs for each channel. A delay can be set to a short delay of a few milliseconds (be aware that this can change the tone quite radically, so experiment with finding the right delay time which works for you), and similarly, chorus can be set to be relatively subtle.

A Few Ideas
Here are two of my favourite parallel effect tricks:

Instruments with two separate outputs - If you have an electric guitar with a piezo bridge, you can use this to drive a second effects chain. A similar thing is to have a two pickup electric guitar or bass modified, so that each pickup feeds it's own output jack. Even if you don't process the two branches separately, combining the two with a mixer gives you a different sound than doing so with the passive switch in the instrument This works especially well when you have an instrument where each pickup sounds great by itself, but has a nondescript sound with both together.

Dynamic delay - I will often compress one branch and use a delay on the second. When I play softly, the compressed branch stands out as the compressor is boosting the level. As I play harder, the louder the delayed branch becomes, while the compressed one stays at a constant level. This means that the delay only becomes audible as I accent beats. This trick works with almost any effect on your second branch.   If you use a stereo delay and pan it hard left and right while the compressed branch is panned to the centre, the delays bounce around the extremes, with the compressed sound rock solid in the centre.

Comb filtered branches - Use a graphic equaliser on each branch. On the first EQ, cut every second frequency band by about 6dB or more and boost the other bands by the same amount. Now reverse these settings on the EQ on the second branch. This gives you two totally different tonalities, which fit together perfectly in a mix. For a guitar sound, try adding overdrive to each branch (either before or after the EQ - it will sound quite different depending on the order).

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Copyright 2009 Alan Ratcliffe. All rights reserved.