PreSonus Blog

Amp Sims: Garbage In, Garbage Out

An astute Friday Tip reader commented that while the tip on how to level the outputs of amp sim presets was indeed useful, I should also write about the importance of input levels. Well, I do take requests—and yes, input levels are crucial with amp sims.

Physical amp sims are forgiving. They soak up transients, and chop off low and high frequencies. But amp sims tend to magnify the differences between guitars and playing styles. When going through the same preset, a player who uses a thin flat pick, 0.008 strings, and single coil pickups will sound totally different compared to a player who uses a thumbpick, 0.010 strings, and humbuckers. So, let’s look at four common mistakes people make when feeding amp sims.

  1. Dialing up presets created by someone else. You have no idea what kind of input level the amp sim expects, so you’ll almost certainly need to edit at least some parameters (particularly the input drive or level).
  2. Too much gain. Excessive gain generates nasty distortion, not the “good” distortion an amp creates. You’ll also have issues with decreased definition, potential aliasing, and a sound that splatters all over a mix. Check out the audio example, using Ampire’s Painapple amp.

The first half has the input set to 5 o’clock. Not only is the sound so distorted the playing is indistinct, listen to the very beginning, before the first note hits. All that gain is picking up noise, hum, and garbage that becomes part of your guitar signal. No wonder the amp sim sounds like garbage—it has plenty of garbage mixed in. The audio example’s second half has the input at 9 o’clock. The sound is not only more focused, but stronger.

  1. Inconsistent levels. Amp sim plug-ins are always re-amping—the guitar track is dry. Because amp sims are so dependent on levels, consistent sounds from presets require consistent track levels. I normalize my dry guitar tracks to -3 dB, and then my presets know what to expect. Also, note that Event level adjustments are before the amp sim. Sometimes all that’s needed to optimize the guitar sound is to lower the Event level in places where you want more definition, and raise it when you prefer heavier distortion.
  2. Too many low and high frequencies. Guitar amps were never about flat frequency response. Rolling off lows below the guitar’s range keeps out bass energy that has nothing to do with your playing, and rolling off the highs a bit simulates the high-frequency loss through long cables—something amp sims don’t emulate. In the next audio example, the first half is the same overly distorted sound as the previous audio example’s first half. The second half doesn’t change the input level, but rolls off the lows and highs with the Pro EQ, prior to the amp sim. Fig. 1 shows the Pro EQ settings.

Figure 1: Rolling off the lows and highs before feeding an amp sim can clean up the sound.

In particular, listen to the spaces between notes. The version without EQ has a sort of bassy mud between notes that detracts from the part’s focus.

The bottom line is simple: If your amp sim doesn’t sound right, the quickest fix might be as simple as turning down the input level, and rolling off some lows and highs before the amp sim.