Kemper Profiling Amplifier Manual - page 52
KEMPER PROFILING AMPLIFIER
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probably sound weird and uninspiring on its own, but when you engage the “Rotary speaker” stomp in the
MOD module, you’ll hear the rich and animated sound of your original rotary cabinet.
✔
✔
Tip: Although the profile is captured in mono, you can use the “Rotary speaker” stomp in the MOD or X
slot to recreate the typical stereo movement of the signal. The Rotary speaker effect will automatically
separate the bass rotor from the tweeter horn.
Under the hood
In case you enjoy reading about technical details, below is a description of what the KPA is doing during
the profiling process:
During the first phase, you will hear white noise with a rising amplitude. The KPA is now collecting data
about the frequency response of the reference amp. The frequency response will change dramatically as
the gain increases. This is how the KPA learns about the circuitry of the reference amp and the frequency
response of the cabinet. Also, the characteristic impedance curve of the speaker, including its feedback to
the power amp, is detected in fine detail.
In the next phase, slowly pulsating white noise is sent to the reference amp. The volume of the white noise
is set to a level at which the reference amp starts to distort. This is how the KPA learns about the dynamic
distortion curve of the tubes in the reference amplifier. Using this information, the KPA is able to recreate
that curve with the highest possible accuracy. This is also true for transistor-based and digitally-modeled
distortions.
In the third step, the KPA sends a complex tonal texture that follows a mathematically-based set of rules
to the reference amp. This texture creates unique interference patterns that allow the KPA to take a “fin-
gerprint” of the DNA of the reference amp’s particular sound. The distortion of the speaker, along with
the partial pattern of the loudspeaker diaphragm (also known as “cone breakup”) are excited by this tonal
mixture. They complete the characteristic interference pattern that the KPA will reproduce faithfully, once
the measurements have been taken.
If the reference amp is clean, the KPA skips the third phase (because there is no distortion to be mea-
sured).