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Kemper KPA Effects

The Kemper Profiling Amp comes equipped with lots of effects models, covering basically all the normal types of effects used for guitar and bass. Its design philosophy is not to provide lots of variations of each type or software models of real-world popular/classic effect models, but to provide one or a few highly-configurable models of each effect type, allowing a wide variety of sounds from each one, including emulating real world gear. There are a few exceptions to this general principle due to impossibilities in making them configurable such as distortions, shapers, and reverbs, as well as making the user interfaces less overwhelming in the cases of the wahs and delays.

My goal for this page is not to walk through every effect in the unit, or describe how to get particular sounds based on artists or real-world gear - WiKPA.org already does a great job of that. I'm also assuming you already know about how typical guitar effects work and sound and how to tweak them, as well as how to place effects in the KPA's signal chain. What I'm covering are specific quirks in some effects, clarifications for things that might not be intuitive, and exposes for nifty features that aren't readily apparent.

Noise Gates

The Noise Gate controlled by the big Noise Gate Knob on the front of the unit is actually part of the Input block. If you lock Input (I recommend doing so), you will always use that Noise Gate setting. Also, it is not a traditional noise gate but more of a noise remover or noise suppressor, which can leave artifacts when set fairly high. For these reasons, I like to use a rather low value here - just enough to suppress some noise when muting the guitar strings.

The 2:1 and 4:1 Gate effects are the true expansion-based noise gates, and they work very well. These are the ones to use for high-gain patches where you need dead silence when muting the guitar strings. The difference between the two is the expansion ratio they use. The 2:1 Gate effectively halves the volume of the signal if the original signal is lower than the Threshold value you dial in. The 4:1 Gate basically doubles that, making the volume 1/4 of what it is originally. For punchy chord/silence/muted chord/silence djent-type riffing, I like the 4:1 Gate. For leads or more traditional hard rock, I prefer the 2:1 Gate - it's enough to achieve silence while muting but won't noticeably decay sustained notes too quickly.

I use fairly high-output passive pickups, and a Threshold setting of 3-4 is quite enough. If you find yourself needing to go much higher to achieve silence, this indicates some other issue, either in your guitar electronics, pickup height, gain setting, or pickups themselves.

All those Wah Choices

All those Wah Wah choices can initially look intimidating and confusing. Many are simply manual control over typical modulation effects, but their own type here to be automatically controlled by an expression pedal assigned to CC# 1 (Wah). Here's the break down:

  • Wah Wah - this is the basic wah wah pedal, a band pass filter.
  • Wah Low Pass - rather than a bank pass filter, the wah is a low pass; goes from dark to full
  • Wah High Pass - rather than a bank pass filter, the wah is a high pass; goes from full to thin/shrill
  • Wah Vowel - filter simulating a talkbox effect by emphasizing formants through the sweep
  • Wah Phaser - a phaser effect where you manually control the sweep instead of an LFO
  • Wah Flanger - a flanger effect where you manually control the sweep instead of an LFO
  • Wah Rate Reducer - controls the sample rate, causing distortion and aliasing, glitchy sounds
  • Wah Ring Modulator - controls a sine wave frequency fed into the signal for modulation
  • Wah Frequency Shifter - a ring modulator that only allows for harmonic frequencies - sounds like radio tuning modulation
  • Wah Formant Shifter - controls formant shifting of single notes. center position is normal, basically no processing. while the vowel filter changes an EQ-like sweep over one formant type, this shifts the formant types themselves

Mono vs. Stereo

Although Stomps A-D, X, and Mod can all load the same effect types, some of them will function differently depending on placement. The Stomps section is limited to mono effects. Their stereo nature would have to be mixed down to mono to get processed by the Stack section anyway. For such effects, you may notice an extra Stereo Separation parameter when using them in the X or Mod slots. These use various techniques to "widen" their sound. Many effects, such as the Air Chorus and Stereo Widener, will not sound correct unless used as stereo effects.

Delay and Reverb

The KPA's Delay and Reverb blocks are special in that they can only load those types of effects (Delay will actually open up for general purpose usage in OS/FW 4.0). This is for good reason - the KPA's design treats them special. The wet portion of the combined Delay and Reverb blocks is accessible through the "Delay/Reverb Wet" output option that can be assigned to the Main or SPDIF outputs.

Additionally, the Reverb block has a "Del./Reverb Balance" parameter that greatly simplifies what would otherwise require a complicated routing and mixing setup. The Delay block outputs a wet (delay trails) and dry (unaffected by Delay) signal to the Reverb block. The Del/Reverb Balance setting chooses the proportion at which the reverb applies to each of these signals. At full left, the reverb applies only to the dry signal, not to the delay trails. At full right, the reverb only affects the delay trails, not the dry signal. At other settings, the reverb applies to both but at different amounts. This is a powerful control - when used in combination with a 100% wet reverb, you can set it fully right so that the delay trails are washed into a reverb, allowing for some very neat sounds (see below).

Tone Controls

Both the Delay and Reverb blocks feature Frequency and Bandwidth settings that affect the frequency response of the blocks. The Bandwidth control is essentially a Q control, narrowing the range of frequencies allowed to pass through as you turn it higher and higher. At 0, it is doing nothing. At max, it is only allowing a very, very narrow range of frequencies through.

In OS 4.0, these controls are switched to high-pass/low-pass filters with configurable frequencies and 2 possible "slopes" for delay effects. These are easier to utilize than the bandwidth/frequency paradigm, but the filters themselves still operate as described below.

These controls function slightly differently in the Delay block vs. the Reverb block. Reverb's can be considered a filter on the wet part of the block's output after all processing. When set to 100% mix, it is the same thing as placing an EQ after the reverb. The Delay controls operate inside the delay's feedback loop. This means that as the same segment of audio repeats over and over, it is filtered more and more each iteration.

This is similar to the Reverb's Dampening control, which darkens the tone of the wet reverb as it decays based upon its Time setting. However, while Dampening can only darken the wet signal over time, the Delay's tone controls can brighten or darken the signal over time.

I find that the most natural sounding delay and reverb tend to darken the tone over time, as well as apply greater reverb to the delay trails than to the dry signal. Thus, I often use the Delay's Bandwidth and Frequency controls set to slightly darken the trails, as well as use the Reverb's Dampening. I usually set Del/Reverb Balance about 30% right of center. I use the Reverb's Bandwidth/Frequency for any final tonal adjustments.

However, there are numerous unique applications for the interaction of all these controls I attempt to explore below...

MAB Advanced Reverb Effects

A big complaint about the KPA is its lack of great reverb effects, particularly a spring reverb. I attempted to create some advanced reverb presets that fill this void until Kemper adds them. See the MAB Advanced Reverb Presets page.

Differences in Delay Types

Note: OS 4.0 converts the 3 delay types in the legacy section below into a Legacy Delay type, preparing for 5.0 to introduce a slew of new delay types.

OS 5.0 Delays

While there are a large number of delay effects listed in OS 5.0, they all boil down to a few core delay types with different features available:

  • Two-Tap Delay - features two delays that function in tandem, not independently. The first setting is the baseline setting, while the other is the offset of the first. So you can get pairs of delays such as 100ms, 120ms, 200ms, 220ms, 300ms, 320ms...
  • Serial Delay - this is essentially two delays built into one effect, with the output of the first feeding directly into the input of the second. The second delay will repeat the raw guitar as well as the trails of the first.
  • Dual Delay - two fully independent delays functioning in parallel. Thus, you can have 30ms, 60ms, 90ms, 120ms... in the left field and 100ms, 200ms, 300ms... in the right.
  • Melody Delay - this is similar to the two-tap delay in that the same delay pattern will repeat against the first delay's baseline time; however, each delay here can be set to different pitch-shifter settings. Variants for chromatic and harmony pitch-shifting are provided. This can be used to play arpeggios or scales via delay trails.

Many of the new delays have the same great feature set, with two different kinds of modulation, (transient) smearing, attack swelling, reversing, hold/infinite feedback, crystal/shimmer (progressive pitch-shifting in the feedback loop), and both tape distortion and wow/flutter emulation.

But perhaps the most interesting new feature is Super Stereo on the Stereo parameter. Stereo can be set to <0.0> at dead center, which means each of the delays will be panned to center. Moving left to -100% or right to 100% pans each delay full L/R or the opposite R/L. Going beyond 100% up to 200% in either direction engages "Super Stereo", which uses some EQ or phase trickery to make the delays sound even wider and even three-dimensional, like they are coming from the sides and back of the room.

Legacy Delays

There are only 3 delay types, explained below. Note, although it may seem these feature separate L/R timings, these are actually two-tap delays, where the L and R delay trails always have the same offset timing between each other. This means you may not get the results you expect. For instance a 2:4 ratio delay is not the same thing as a 4:2 ratio delay with L/R reversed!

  • Tap Delay - uses the tempo on the rig (tapped or manually entered), with separate L/R delay settings defined in terms of 16ths of a beat. This offers the most flexibility between the left and right delays, offering ratios (3:5 or 5:7) that are not found in the other delay types. However, it is not capable of offering repeats as quickly as the other delay types because it is always tied to a tempo setting that cannot go fast enough to allow such.
  • Free Delay - can use the rig's tempo or can be manually specified when tempo is disabled. This offers repeats as short as 1 ms! However, there is only a single Time setting. A Ratio parameter determines the ratio of left repeats to right repeats, with the only options being quarters of the other (1:4, 2:4, 3:4, 4:4, 4:3, 4:2, 4:1).
  • Analog Delay - is the exact same thing as Free Delay, with the exception that if you change the Time parameter while repeats are occurring the repeats are pitch shifted as occurs on an analog delay pedal. There are no tonal differences to this type compared to the other two.

All three Delay types exhibit a tape delay simulation when using Feedback settings around 90% or higher. Anything lower is a straight digital delay.

Tempo Considerations

Tempo can be viewed, locked, changed, and disabled from the Rig block's settings. This mainly affects the Delay block's operation.

When tempo is disabled, the Free and Analog Delays use the Time parameter to determine how quickly they repeat. The Tap Delay uses a default tempo of 120 bpm. When tempo is enabled, the Delays ignore the Time parameter and use the tempo setting. The Tap Delay defines the left and right repeats separately in terms of a beat. The Free and Analog delays use a single Ratio parameter - the beat synchs up to the larger one. For example, a ratio of 1:4 on a 120 bpm tempo means the left delay is set to 30 repeats per minute and the right delay is set to 120 repeats per minute.

Space Effect

In addition to Delay and Reverb, there is an effect called Space that operates similarly to a reverb, perhaps with very subtle delay thrown in, as well as a stereo widening type effect. This effect was designed to make the sound of headphones sound more like the sound of a room. It was originally created just as an option in the Output section for headphones, but can now be applied to all outputs, or assigned as an effect block with different settings per rig.

Pitch Shifter Options

The KPA offers chromatic and intelligent (harmony) pitch shifting effects, which function like traditional pitch shifters. The Harmony Shifter goes a step beyond and allows custom user scales to harmonize against. But even beyond these functions, the KPA's shifters offer somewhat unique options to adjust how the shifters work:

Smooth Chords

The Smooth Chords option disables the shifter's pitch tracking. Tracking is used to phase align the time-shifted audio segments, so that the resulting audio sounds smooth and natural. This works great for single notes but cannot work correctly for chords. Instead, it may jump between pitches as it detects them or phase-align one pitch while the others in the chord end up sounding more harsh. Smooth Chords prevents these awkward sounds when playing chords.

While Smooth Chords is designed to reduce artifacts when playing chords, it may be useful even for single notes depending on how convoluted the signal chain is. It can also yield more of the artifacts traditionally associated with pitch shifters, that while obvious and artificial, may produce a certain desirable sound.

Pure Tuning

This option harmonizes to the Pure Tuned or Just Intonation intervals instead of the 12-Tone Equal Temperament intervals. This makes the harmonized sound a bit more pleasant and harmonious when mixed with the dry signal, particularly when playing higher up the fretboard. See Equal Temperament and Alternate Tunings for more about temperament and tuning.

Formant

The Formant option enables a formant parameter which defines a resonant peak (formant) in the pitch-shifted part of the signal. Formants determine what the tone sounds like, with the human voice making use of different formants to create the different phonetic sounds of the alphabet, particularly for vowels. Thus, the pitch-shifted sound can become quite different from its normal sound. It can reduce the "Chipmunks" type sound to upwards shifted settings. It can also make the guitar sound like a different instrument altogether.

Shapers

While most effects are more common for guitarists, the "shaper" effects may seem a bit confusing. Essentially, they attempt to "shape" the waveforms of the input audio signal. This is essentially what distortion is, but most distortion circuits use clipping to reshape the waves. These do something different entirely, but most end up adding harmonic overtones. The best advice is to try all of them at mild and hot settings, run both into a clean amp profile as well as crunchy one.

Looking at stomps presets, many tend to use a combination of a shaper effect and distortion effect (and sometimes an EQ as well) to emulate various real-world distortion boxes, particularly fuzz type distortion.