How to Make Amp Sims Sound More “Analog”

This Simple Technique Can Make Amp Sims Sound Warmer and More Organic

by Craig Anderton

All amp sims that I've used exhibit, to one degree or another, what I call  "the annoying frequency." For some reason this seems to be inherent in modeling, and adds a sort of "fizzy," whistling sound that I find objectionable. It may be the result of pickup characteristics, musical style, playing technique, etc. adding up in the wrong way and therefore emphasizing a resonance or it may be something else...but in any event, it detracts from the potential richness of the amp sound.

This article includes audio examples from Avid’s Eleven Rack and Native Instruments’ Guitar Rig 4, but I’m not picking on them – almost every amp sim program I’ve used has at least one or two amps that exhibit this characteristic. It also seems like an unpredictable problem; one amp might have this “fizz” only when using a particular virtual mic or cabinet, but the same mic or cabinet on a different amp might sound fine.

Normally, if you found this sound, you'd probably just say "I don't like that" and try a different cabinet, amp, or mic (or change the amp settings). But, you don't have to if you know the secret of fizz removal. All you need is a stage or two of parametric (not quasi-parametric) EQ, a good set of ears, and a little patience.

BUT FIRST...

Before getting into fizz removal, you might try a couple other techniques. Physical amps don’t have a lot of energy above 5kHz because of the physics of cabinets and speakers, but amp sims don’t have physical limitations. So eEven if the sim is designed to reduce highs, you’ll often find high-frequency artifacts, particularly if you run the sim at lower sample rates (e.g., 44.1kHz). One way to obtain a more pleasing distorted amp sim sound is simply to enable any oversampling options; if none are available, run the sim at an 88.2kHz or 96kHz sample rate.

Another option is removing unneeded high frequencies. Many EQs offer a lowpass filter response that attenuates levels above a certain frequency. Set this for around 5-10kHz, with as steep a rolloff as possible (specified in dB/octave; 12dB/octave is good, 24dB/octave is better). Vary the frequency until any high-frequency “buzziness” goes away.

Similarly, it’s a good idea to trim the very lowest bass frequencies. Physical cabinets—particularly open-back cabinets—have a limited low frequency response; besides, recording engineers often roll off the bass a bit to give a “tighter” sound. A quality parametric EQ will probably have a highpass filter function. As a guitar’s lowest string is just below 100Hz, set the frequency for a sharp low-frequency rolloff around 70Hz or so to minimize any “mud.”

FIZZ/ANNOYING FREQUENCY REMOVAL

Although amp sims can do remarkably faithful amp emulations, with real amps the recording process often “smooths out” undesirable resonances and fizz due to miking, mic position, the sound traveling through air, etc. When going direct, though, any “annoying frequencies” tend to be emphasized.

Please listen to this audio example on the Harmony Central YouTube channel.

The sound is from Avid’s Eleven Rack; the  combination of the Digidesign Custom Modern amp, 2x12 Black Duo Cab, and on-axis Dyn 421 mic creates a somewhat “fizzy” sound. Listen carefully while the section plays that says original file, and you'll hear a high, sort of "whistling" quality that doesn't sound at all organic or warm, but "digital."

Follow these steps to reduce this whistling quality.

1. Turn down your monitors because there may be some really loud levels as you search for the annoying frequency (or frequencies).

2. Enable a parametric equalizer stage. Set a sharp Q (resonance), and boost the gain to at least 12dB.

3. Sweep the parametric frequency as you play. There will likely be a frequency where the sound gets extremely loud and distorted—more so than any other frequencies. Zero in on this frequency.

4. Now use the parametric gain control to cut gain, thus reducing the annoying frequency.

In the part of the video that says sweeping filter to find annoying frequency, I've created a sharp, narrow peak to localize where the whistle is. You'll hear the peak sweep across the spectrum, and while the sharp peak is sort of unpleasant in itself, toward the end (in the part that says here it is!) you'll note that it's settled on that whistling sound we heard in the first example. In this case, after sweeping the parametric stage, the annoying whistle is centered around 7.9kHz.

In the next example that says now we'll notch it out, you'll hear the whistle for the first couple seconds, then hear it disappear magically as the peak turns into a notch (check out the filter response in Fig. 1). Note how the amp now sounds richer, warmer, more organic, and just plain more freakin' wonderful A little past the halfway point through the clip, I switched the filter out of the circuit so the response was flat (no dip). You'll hear the whistle come back.

Fig. 1: Here's what was used to remove the fizz. This single parametric notch makes a huge difference in terms of improving the sound quality.

DUAL NOTCH TECHNIQUES AND EXAMPLES

Sometimes finding and removing a second fizz frequency can improve the sound even more; check out Example 2 in the video.

First you'll hear the original file from Guitar Rig's AC30 emulation. It sounds okay, but there’s a certain harshness in the high end. Let’s find the fizzy frequencies and remove them, using the same procedure we used with the Eleven Rack.

After sweeping the parametric stage, I found an annoying whistle centered at 9,645 Hz. The part called annoying fequency at 9645 Hz uses the parametric filter to emphasize this frequency,  while the part labelled notch at 9645 Hz has a much smoother high end. But we’re not done yet; let’s see if we can find any other annoying frequencies.

The section labelled annoying frequency at 5046 Hz again uses a filter to emphasize this frequency. The next section, with notches at 9645 Hz  and 5046 Hz has notches at both frequencies (Fig, 2). 

Compare this to original file at the end without any notches; note how the version without notches sounds more “digital,” and lacks the “warmth” of the filtered versions.

Fig. 2: The above image shows the parametric EQ notches that were applied to the signal, using the Sonitus EQ in Cakewalk's SONAR DAW.

MUCH BETTER!

Impressive, eh? This is the key to getting good amp sim sounds. Further refinements on this technique are:

• Experiment with the notch bandwidth. You want the narrowest notch possible that nonetheless gets rid of the whistle, otherwise you'll diminish the highs...although that may be what you want. As I said, experiment!
• Some amp sims exhibit multiple annoying frequencies. On occasion, sometimes three notches is perfect. Generally, the more notches you need to use, the more narrow you need them to be.

When you’re done, between the high/low frequency trims and the midrange notches, your amp sim should sound smoother, creamier, and more realistic. Enjoy your new tone!

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 Craig Anderton is Editorial Director of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.