Filter block

Available on which products

• Axe-Fx III: 4 blocks
• FM3: 4 blocks
• FM3: 4 blocks
• Axe-Fx II: 4 blocks
• FX8: 2 blocks
• AX8: 2 blocks

Channels or X/Y

• Axe-Fx III and FM9 and FM3: 4 channels
• Axe-Fx II: no
• AX8: X/Y
• FX8: X/Y

Filter types

A filter is a very versatile effect. Examples include:

• one-band equalizer
• boosting the input of an amp block
• boosting the overall signal level (i.e. for leads)
• high-pass or low-pass filtering
• envelope filter / auto-wah
• finding the resonant frequency of your guitar cabinet

The Filter block provides these types:

1. Null
2. Lowpass
3. Bandpass
4. Highpass
5. Lowshelf
6. Highshelf
7. Peaking
8. Notch
9. Tilt EQ
10. Lowshelf 2
11. Highshelf 2
12. Peaking 2
13. FF Comb
14. FB Comb
15. Allpass

Lowshelf and Highshelf

"A lowpass with "direct" signal mixed in is a lowshelf. A highpass with direct signal mixed in is a highshelf. In fact in the analog domain that's a common way of making low/high shelf filters. It's intuitive as well. Take the direct signal and add/subtract some lowpass filtered signal. Now you have a bass boost/cut, i.e. lowshelf." [1]

Lowshelf 2 and Highshelf 2

These filters recreate the analog shelving filters found on classic mixing consoles. These filters are somewhat quirky and exhibit “overshoot” which gives them a certain musical quality. Set Q between 0.5 and 0.707 to recreate those classic sounds, or experiment with Q for different amounts of overshoot. These filter types are great for getting that massive sound associated with passive equalization.

"The Lowshelf2 and Highself2 types are "analog" types and derived using "k + low/high pass"." [2]

Peaking 2

Many “classic” graphic equalizers use variable-Q designs which may be more familiar to some users as opposed to constant-Q filters.

"Peaking 2 is constant Q. At +/- 12 dB they are the same. At other gains the Peaking 2 will have a wider bandwidth as the Q does not change." [3]

Notch

"Gain doesn't apply to a notch filter. Only frequency and Q are relevant." [4]

Tilt EQ

Tilt EQ is a slope filter that allows broad adjustment of the tone using just two parameters: Frequency and Gain. The Gain parameter sets the maximum gain of the filter relative to the center frequency. For example, a gain of 10 dB would set the maximum gain to 10 dB. The gain at the center frequency would be 0 dB and the minimum gain would be -10 dB, therefore a total of 20 dB of EQ would be applied.

FF Comb and FB Comb

FF Comb is a feed-forward comb filter and FB Comb is a feedback comb filter. Delay Time controls the order of the comb filters, higher values result in more closely spaced notches and vice-versa. Depth controls the intensity of the filter, higher values result in deeper notches/peaks and vice-versa.

Slope

Allpass

This is a multi-stage “Phase Rotator” with feedback. With feedback set to zero, it can be used to change the shape of transients. Using feedback causes constructive and destructive interference and can be used to create interesting tonalities. The Order can be set from 1 to 12 with progressively more phase rotation occurring. Attaching a modifier to the Frequency parameter can result in interesting chorus or wah effects. The red trace in the GUI is the phase response.

Tips, tricks and troubleshooting

Factory presets

The Filter block is showcased in many factory presets. Search the Factory presets page for "filter".

Adapt a preset to multiple guitars

Read this: Use Filter and Scene Ignore to adapt a preset to multiple guitars

Dynamic Distortion

Some filter types are also available in other effect blocks, such as the Dynamic Distortion block.

Sweep frequencies

Attach the global LFO controller or the LFO in the Filter block to the Frequency parameter to generate frequency sweeps, as demonstrated in many Factory presets.

Envelope filter (Auto Wah)

Fractal Audio devices don't provide a dedicated Auto Wah effect block. You can achieve this effect by attaching the Envelope controller to a Filter or a Wah block. Attack is the time it takes to go from silence to maximum level. Release is the time it takes to drop from sustain level to silence after being released.

Try Factory presets such as: PSYCHADELIC CDUCK, FRENETICA, TRACK WAH.

Lof-fi filter sweep

Watch the video below for a lo-fi filter trick.

80's rock sound

"This was a common technique in the 80's when tracking. If you have an Axe-Fx or other modeler with EQ options you can try it yourself. Put an EQ or Filter block before the amp. A parametric is best. Set the type to Peaking, Frequency to 1 kHz and Q to around 1 and gain to around 6 dB to start. Experiment with the parameters."

The Axe-Fx III, FM9 and FM3 let you obtain the same result using Pre EQ in the Amp block.

Boston / Rockman sound

Put a Filter block in front of a Plexi amp model, select Peaking, set Frequency at around 800 Hz, Q at 0.707 and Gain at 12 dB.

Eric Clapton mid-boost

To emulate Eric Clapton's mid-boost knob on his guitars:

"Use the Filter block. Since the max boost is 25 dB set the filter order to 4th which will give you a maximum of 24 dB. Set the type to Peaking. Set freq to 500 Hz. Vary gain and Q to taste." [5]

Clean boost

Set the Filter to "Null", set its Level to where you like it, put it at the end of the signal chain, and assign a switch. Now you have a simple, low-CPU, clean boost at your disposal.

Find the resonant frequency of a guitar cabinet

Read this: Finding the resonant frequency with a solid-state amplifier

Alternative to Boost in the Amp block

The Boost parameter in the Amp block boosts the signal at the input of the Amp block. If you rather have an boost with adjustable EQ, use a Filter block before the Amp block.

Alternative to Crossover block

There's no Crossover block in the FM3. Filters can be used to achieve something similar. Check out the FM3 factory preset POLYFUZZ CROSSOVER.

Alternative to a cabinet

A Filter can be used to create an "amp+cab-in-the room" sound. Watch the video below.

Boosting mids with FRFR amplification

A mid-boost can be help a guitar cut through the mix when using FRFR amplification. Try a Filter at the end of the grid, select Peaking, Frequency at 770 hz, Q at 0.35, Gain between 2 and 4 dB.