Kurzweil KDFX, Manual

Page: 53 / 164

Inside KDFX
Output section
3-21
Digital Word Length
The K2500 is capable of producing 20-bit digital audio signals. While normal 16-bit digital
audio provides a maximum dynamic range of about 96 dB, adding the extra four bits adds
some 24 dB to the dynamic range. There are an increasing number of products on the market
that can handle 20-bit digital signals, including tape and hard-disk recorders, mixers, and
signal processors, and the K2500 can talk to these devices with the highest degree of Þdelity.
The Ò DigOut Ó parameter at the bottom right corner of the EffectsMode page turns on this
feature, and selects between 16-bit and 20-bit operation.
This setting determines the word length on the KDS eight-channel output, and also on the
AES/EBU output, provided it is in ÒDirectÓ mode (as set on the
SampleMode pageÑsee the
previous section).
If you are using the K2500 with a Kurzweil DMTi, this switch should be set to Ò16 BitÓ, since the
DMTi currently operates only in 16-bit mode. However, if you are connecting the AES/EBU
output to a 20-bit (or more) capable device, set the switch to Ò20 BitÓ and you can take
advantage of the signiÞcantly reduced noise ßoor.
Note that the switch does not affect any of the K2500Õs inputs: those are always operating in
16-bit mode.
Dither
Dithering is a technique in which a small bit of noise is added to a digital signal when you are
shortening the digital word length, e.g., from 20 bits to 16 bits. Its effect is to remove
quantization distortion that otherwise may result in strange modulation artifacts at low levels.
The subjective effect, paradoxically enough, is often that the apparent noise ßoor of the
processed signal is lowered. The Dither parameter at the bottom left of the
EffectsMode page
allows you to select between different digital noise ßoor characteristics. No setting is superior
to anotherÑeach one is a tradeoff between perceived noise level and artifacts. Here is a brief
explanation of each setting:
Flat Ñthe digital noise ßoor is spectrally ßat, so it's a good choice for re-sampling the K2500Õs
own output, as there will be no adding of noise in the process. This is sometimes known as
ÒtriangularÓ dither.
Minimum , Medium , Maximum Ñthese utilize noise-shaping in varying degrees. The noise
ßoor has been essentially equalized to make it softer at midrange frequencies, and louder at
bass and treble frequencies. The overall power level of the noise is actually higher than at the
Flat setting, but due to the ear's spectral response at low levels, the noise ßoor appears lower at
these settings.
Table 3-1. AES/EBU output switch settings
Digital ÒOutÓ switch Analog ÒSrcÓ switch WhatÕs on the AES/EBU
output
Dir n/a KDFX output A
A/D Int K2500 Mix output
A/D Ext K2500 analog input