User manual KURZWEIL KDFX V2 MUSICIANS REFERENCE REV B

[. . . ] Permission is granted to reprint up to two copies of this manual for personal use. ®, KDFX®, Pitcher®, and LaserVerb®, KSP8 TM, K2600TM, K2500TM, and K2000TM are trademarks of Young Chang Co. , Ltd. All other products and brand names are trademarks or registered trademarks of their respective companies. Product features and specifications are subject to change without notice. Part Number: 910379, Rev. [. . . ] The aliasing component simulates the effect of having sampled a sound without adequately band limiting the signal (anti-alias filtering). Quantization distortion is a digital phenomenon caused by having only a limited number of bits with which to represent signal amplitudes (finite precision). You are probably aware that a bit is a number which can have only one of two values: 0 or 1. When we construct a data or signal word out of more than one bit, each additional bit will double the number of possible values. For example a two bit number can have one of four different values: 00, 01, 10 or 11. A three bit number can take one of eight different values, a four bit number can take one of sixteen values, etc. An 18-bit digital-to-analog converter (DAC) like the one in the K2600 can interpret 262, 144 different amplitude levels (218). Let's take a look at how finite precision of digital words affects audio signals. The figures below are plots of a decaying sine wave with varying word lengths. (i) (ii) (iii) (iv) Figure 9 A decaying sine wave represented with different word lengths: (i) 1-bit, (ii) 2-bit, (iii) 3-bit, (iv) 4-bit. 3-23 Algorithm Reference Quantize+Alias Clearly a one-bit word gives a very crude approximation to the original signal while four bits is beginning to do a good job of reproducing the original decaying sine wave. When a good strong signal is being quantized (its word length is being shortened), quantization usually sounds like additive noise. But notice that as the signal decays in the above figures, fewer and fewer quantization levels are being exercised until, like the one bit example, there are only two levels being toggled. Controlling the bit level of the quantizer is done with the DynamRange parameter (dynamic range). Every 6 dB adds approximately one bit, so at 144 dB, the word length is 24 bits. The quantizer works by cutting the gain of the input signal, making the lowest bits fall off the end of the word. At very low DynamRange settings, the step from one bit level to the next can become larger than the input signal. The signal can still make the quantizer toggle between bit level whenever the signal crosses the zero signal level, but with the larger bit levels, the output will get louder and louder. When the DynamRange parameter is lower than the Headroom parameter, no more signal boost is added to counter-act the cut used to quantize the signal. Find the DynamRange level at which the output starts to get too loud, then set Headroom to that level. You can then change the DynamRange value without worrying about changing the signal level. Headroom is a parameter that you set to match your signal level, then leave it alone. At very low DynamRange values, the quantization becomes very sensitive to DC offset. By adding positive DC offset, the signal will tend to quantize more often to a higher bit level than to a lower bit level. [. . . ] Parameters: Page 1 In/Out Harmonics Fund FreqC Fund FreqF (HarmonicSuppress) In or Out Even, Odd, All 8 to 25088 Hz -100 to 100 ct SC Input ExpandChan L, R, L & R L, R, L & R Out Gain Off, -79. 0 to 24. 0 dB Page 2 Atk Time Rel Time SmoothTime Signal Dly 0. 0 to 228. 0 ms 0 to 3000 ms 0. 0 to 228. 0 ms 0. 0 to 25. 0 ms |||||||||||||||||||||||||||||| -dB 40 20 12 8 6 4 2 Reduction 0 Ratio Threshold MakeUpGain 1:1. 0 to 1:17. 0 -79. 0 to 0. 0 dB Off, -79. 0 to 24. 0 dB In/Out Out Gain When set to In the expander is active; when set to Out the band suppressor is bypassed. The output gain parameter may be used to increase the gain by as much as 24 dB, or reduce the gain to nothing. Note that the Out Gain parameter does not control the signal level when the algorithm is set to Out. The coarse frequency control sets the fundamental frequency of the harmonic structure to be expanded. [. . . ]