Big Sounds With Virtual Stacks

In the 11/09 issue, we covered virtual amp stacking techniques for bass. Now, let’s stack things up from a guitarist’s standpoint. After all, one of the great advantages of amp sims is you can try out sounds that would be a hassle to set up in the “real” world—like stacking two (or more) different amps and cabinets, with different effects, and spreading them out in stereo.
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In the 11/09 issue, we covered virtual amp stacking techniques for bass. Now, let’s stack things up from a guitarist’s standpoint. After all, one of the great advantages of amp sims is you can try out sounds that would be a hassle to set up in the “real” world—like stacking two (or more) different amps and cabinets, with different effects, and spreading them out in stereo.

If you record through a plug-in amp sim in your computer (in this case the track itself is dry, and the final sound results from the amp sim processing the dry track), you can duplicate the dry track and add another amp sim in parallel to stack the sound. But that means you don’t hear the stacked sound until after you’ve played your part, and it’s more fun to play through the stack, as it influences your playing.

Parallel Lines

You’ll want to split your guitar into at least two different paths to feed the different “stacks.” You can do this by inserting amp sims into two different tracks and setting each track’s input to the channel carrying the guitar, then monitoring the input signal through the computer (this function is typically called something like “input echo” or “live monitor”). This lets you hear the effects of any plug-ins. But it’s not always necessary to use two tracks; many amp sim plug-ins can create parallel signal paths (that you can pan anywhere in the stereo field) all by themselves.

With IK Multimedia’s AmpliTube series, there are eight routing options; routing 2 creates two separate, parallel chains. Line 6’s POD Farm has a Dual button that creates two different signal chains, which essentially puts two POD Farms in parallel.

Peavey’s ReValver Mk III and Native Instruments’ Guitar Rig 4 both offer “splitter” modules for their “virtual racks” (Figure 1). These let you split the input signal into two paths, where you can insert whatever amps, speakers, etc. you want. Then, the splits go into an output mixer for mixing and panning. (However, note that Guitar Rig lets you put splits within splits, while ReValver Mk III is limited to one split module per rack.)

Waves’ G|T|R has stereo amps, which provide the same basic function as stacked amps. However, if you want a parallel path where you can add effects and such independently to the two amps, then you’ll need to use two tracks, and two instances of G|T|R.

Fig. 1. This setup emulates the sound of a guitar being split into two different amps and cabinets. The Split module in Native Instruments’ Guitar Rig 4 is sending the guitar through two chains, each of which contributes a different sound. Note how the Split Mix output can crossfade between the two channels and adjust the pan. Also, the B split in the Split Mix section has a phase switch.

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Fun with Stacks

Here are some ways to use stacking in the studio.

  • When mixing, a stereo rhythm guitar with the channels panned oppositely opens up a huge space in the center for bass. It’s almost like having two guitars, but with the simplicity of a single guitar part.
  • Use a tempo-synced effect like tremolo, but set different rhythmic values in the two chains. You can get some wild stereo effects bouncing around.
  • Try three stacks, with power chord sounds left and right, and a bright, chorused acoustic-type sound up the center. Add bass and drums, and you won’t need anything else— the sound can be huge.
  • If there’s a complementary instrument like keyboard or rhythm guitar, pan one channel of your guitar to center, and the other right or left. This “weights” the guitar toward one side of the stereo field. Similarly, weight the other instrument oppositely in the stereo field. Now both instruments take up a decent amount of space, but don’t tread on each other.
  • Splitting isn’t just about amps, but also effects. If you want some great flanging effects, put a vibrato effect set for a slow speed in each split (processed sound only). When you sum the outputs together in mono, the delay variations between the two splits will rock your world.