Amp Sim Fixx

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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 annoyingfrequency." 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 simprogram 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...



How to Make Amp Sims Sound More “Analog”



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 run the sim at an88.2kHz 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 “smoothes 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.

The following audio example 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, and you'll hear a high, sort of

"whistling" quality that doesn't sound at all organic or warm, but "digital."






• FizzySound.mp3

The audio example is the original amp sim sound. Let’s find that fizzy quality,

and get rid of it.

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 frequencywhere the sound gets extremely loud and distorted—more so than any other

frequencies. Zero in on this frequency.

• FindFizzyFreq.mp3

In this audio example, 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 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.

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

frequency – check out the next audio example.

• RemoveFizz.mp3

http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147982/RemoveFizz.mp3

http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147981/FindFizzyFreq.mp3

http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147970/FizzySound.mp3






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 the following screen shot). 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 theresponse was flat (no peak or dip). You'll definitely hear the whistle come back.

Here's what was used to remove the fizz (click to enlarge). 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; let’s investigate.

http://www.harmonycentral.com/servlet/JiveServlet/showImage/102-1652-11-11976/FizzRemoval.JPG






• No notches.mp3

This audio example plays back the original sound from Guitar Rig 4’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.

• FindFreq9645Hz.mp3

After sweeping the parametric stage, I found an annoying whistle centered at 9,645Hz. Now

listen to the next audio example.

• Notch at 9645Hz.mp3

The notch takes out the whistle at 9,645Hz. Note how the high end sounds a lot

smoother. But we’re not done yet; let’s see if we can find any other annoying

frequencies.

• FindFreq5046Hz.mp3

This audio example shows that there's another peak frequency; this time it's centered at

5,046Hz.

http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147986/FindFreq5046Hz.mp3


http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147985/Notch+at+9645Hz.mp3


http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147983/No+notches.mp3






Removing this additional frequency doesn’t make as dramatic a difference as

removing the 9,645kHz range, but it still improves the overall sound...check out

the next audio example.

• Additional Notch at 5046Hz.mp3

This example plays back the original file with both notches added, followed by

the original file without any notches (flat response). Note how the second part

sounds much more “digital,” and lacks the “warmth” of the first half...and alsonote that it's not a subtle difference!

The above image (click to enlarge) shows the parametric EQ notches that were applied to

the signal, using the Sonitus EQ in Cakewalk's Sonar DAW.

http://www.harmonycentral.com/servlet/JiveServlet/showImage/102-1652-11-11977/Notches.JPG

http://www.harmonycentral.com/servlet/JiveServlet/download/1652-11-147987/Additional+Notch+at+5046Hz.mp3






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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Amp Sim Fixx