Elecraft KDSP2 Manual - Manual (Page 46)

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Coefficients
In mathematics, the coefficients of an equation are usually constant values. For example, in the phrase
Ax 2 + Bx + C
A, B and C are coefficients. x is the variable.
In DSP filters, the coefficients define the filter response, and are usually fixed (constants). The sampled
signal is the variable, and the result of the equation is the filtered signal.
In the case of adaptive filters, the coefficients are changed by the DSP as a result of computations, so are
not really constants.
DAC
Digital to Analog Converter. This is a device which accepts a digital value and converts it to an analog
voltage. In the KDSP2, the DAC accepts the16-bit digital information from the DSP chip and converts it to
a differential analog voltage which is applied to the audio amplifier in the K2. It does this 16,000 times per
second.
Decay
In the LMS algorithm, Decay defines how quickly the filter abandons adjustments made in its attempt to
implement the algorithm. If you think in terms of an automatic gain control, it corresponds to the decay
time.
A higher value means more rapid decay.
Decimation
It is sometimes advantageous to reduce the sampling rate of a signal that has already been sampled. The
process of doing this is called decimation. In the KDSP2, the input sampling rate is 16 kHz. The filters
operate better with a sampling rate of 8 kHz. A “decimation by two” operation takes place to change the
sampling rate to 8 kHz from 16 kHz.
Denoiser
A process to remove random noise from a signal. This is usually meant to be thermal noise like the
background hiss of an HF band. Denoisers usually don’t do well against static crashes or impulse (ignition)
noise.