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rdq-6 instruction manual
rdq-6 instruction manual
rdq-6 instruction manual.................................................................................................................................................... 1
introduction............................................................................................................................................................................ 1
physical layout ....................................................................................................................................................................... 3
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front panel controls................................................................................................................................................ 3
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rear panel layout ..................................................................................................................................................... 4
operational guide ................................................................................................................................................................. 5
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input selection ......................................................................................................................................................... 5
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stereo-linked/dual-mono mode ......................................................................................................................... 6
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output wordwidth (dither) selection ................................................................................................................ 6
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volume control......................................................................................................................................................... 7
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individual volume offsets ..................................................................................................................................... 8
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channel selection .................................................................................................................................................... 9
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bypass mode ............................................................................................................................................................ 9
Transparent Tone Control ™ .............................................................................................................................................11
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selecting filters.......................................................................................................................................................11
memory functions ..............................................................................................................................................................13
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save preset ..............................................................................................................................................................13
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load preset ..............................................................................................................................................................14
appendix A: equalization and dither.............................................................................................................................15
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equalization ............................................................................................................................................................15
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dither ........................................................................................................................................................................18
appendix B: the relationship between Q and slope ................................................................................................22
appendix C: finite wordlength digital filtering..........................................................................................................23
appendix D: rdq-6 automation protocol ...................................................................................................................25
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Automation Port Reconfiguration ...................................................................................................................25
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Command Strings .................................................................................................................................................25
specifications........................................................................................................................................................................28
precautions...........................................................................................................................................................................29
warranty.................................................................................................................................................................................30
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other z-systems audio laboratories products...............................................................................................30
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contact information..............................................................................................................................................31
introduction
Congratulations on your purchase of the rdq-6 digital reference equalizer. The rdq-6 is the
result of many years of research and development in digital audio technology, and when used
properly, it will create a home theater experience you may not have thought possible from
your system.
The purpose of this document is to give you a complete understanding of the theory and
operation of the rdq-6 so that you may apply it properly in your home theater system. The
rdq-6 is a six channel digital tone and level control system that is used between an AC-3 or
DTS decoder and six channels of digital-to-analog conversion (realizable as either three
separate two-channel DACs or a single six-channel DAC such as our rdac-6). This is shown
schematically in Figure 1. The rdq-6 offers six bands of parametric equalization for each of six
discrete channels. The parametric equalization can be used for a wide array of purposes,
z-systems audio laboratories
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Table of Contents
Related Manuals for Z Systems rdq-6
Summary of Contents for Z Systems rdq-6
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Page 1: Table Of Contents
The rdq-6 is a six channel digital tone and level control system that is used between an AC-3 or DTS decoder and six channels of digital-to-analog conversion (realizable as either three separate two-channel DACs or a single six-channel DAC such as our rdac-6). - Page 2 Additionally, the rdq-6 allows the user to control master volume, individual channel volume offsets and dither all in the digital domain. With the rdq-6 in the signal path, there is no need for an analog preamplifier; the DAC(s) can be connected directly to the power amplifier(s). In this regard, it is useful to think of the rdq-6 as a digital domain preamplifier for your six- channel home-theater playback.
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Page 3: Physical Layout
2. Signal valid indicators. Separate LEDs indicate the presence of valid digital input signals on the Left/Right Front, Left/Right Surround and the Center/Sub channels. 3. Bypass button. Pressing this button disengages all of the rdq-6's signal processing (with the exception of the volume control) from the signal path. -
Page 4: Rear Panel Layout
10. Infra-red remote sensor. • rear panel layout The only audio connectors visible on the rdq-6's rear panel are three sets of XLR AES/EBU digital inputs and outputs and three sets of RCA S/PDIF digital inputs and outputs. The main power switch and the AC mains connector are also located on the rear panel. -
Page 5: Operational Guide
Surround, and Center/Sub. Each of these cards has two digital inputs and two digital outputs. The rdq-6 allows you to select which of the inputs is active through the input selection function. There are a number of reasons why input source selection is best performed in the digital domain. -
Page 6: Stereo-Linked/Dual-Mono Mode
For a more thorough discussion of dither, please refer to Appendix A. The rdq-6 allows you to control the dither for each processor card so that each of the output signals are compatible with your digital-to-analog converter(s). The rdq-6 carries out its computations in 40-bit floating-point arithmetic, which then must be converted back to a fixed-point representation usable by your DACs. -
Page 7: Volume Control
24-bit output setting for other devices. IGURE How to do it. To select which dither mode is used by the rdq-6, press the system button and WORD select the submenu. The display will appear as shown in Figure 6. To change which... -
Page 8: Individual Volume Offsets
IGURE How to do it. With the rdq-6 in normal operating mode, press the volume button. The display will change as shown in Figure 7. To change the master volume, turn the center knob until the desired value is shown on the display. You can also enter offsets relative to the left front channel for the right front, left and right surround, center and sub channels. -
Page 9: Channel Selection
IGURE How to do it. With the rdq-6 in normal operating mode, press the channel button. Figure 9 shows how the display looks when we are displaying the the Left/Right Front channel settings. To change which channel is being displayed, turn the center knob until the channel you would like to see is shown. - Page 10 When in bypass mode, none of the rdq-6’s controls are functional; you must press bypass again to return to normal mode. IGURE a special note on performing A/B comparisons The italicized text above makes it clear that the bypass control returns the output wordwidth to 24 bits, canceling the dither that may have been selected.
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Page 11: Transparent Tone Control
Transparent Tone Control (TTC) and the TTC facility built into the rdq-6 is its most important feature. TTC is actually more than a tone control; it's a complete digital-domain parametric equalizer that can be used subtly for speaker correction, dramatically for room correction, or artistically, to sculpt the signal and make it sound the way you want it to sound. - Page 12 Figure 11 shows the rdq-6 as if the button for filter 3 had been hit (ignore for now the particular values assumed by the various parameters). In this state, the three knobs control the various parameters for bell filter 1;...
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Page 13: Memory Functions
• save preset IGURE How to do it. Suppose you have dialed in the rdq-6's controls to a setting you find pleasing: you are happy with the bell filters, the shelf filters, the input, and the dither for all six channels. -
Page 14: Load Preset
1 with preset 49; this would be difficult without the a/b controls. You should make note of two particular preset numbers. Loading preset number 0 will return the rdq-6 to a "flat" setting. The flat setting is characterized by: •... -
Page 15: Appendix A: Equalization And Dither
–6 dB. As we vary the slope while keeping the center frequency and gain constant, the bandwidth of the filter changes. As the slope increases, the bandwidth decreases (that is, the filter gets narrower). On the rdq-6, the slope varies from 1 to 12, with a... - Page 16 1 giving the widest bandwidth, and a value of 12 giving the narrowest bandwidth. Figure 15 illustrates this relationship clearly -- as we increase the slope parameter, the 3-dB points will gradually move toward 1000 Hz from the left and from the right and the filter gets narrower and narrower.
- Page 17 So far, we’ve only discussed bell-shaped parametric filters. We will now turn our attention to shelving filters. Whereas bell-shaped filters are used to emphasize or de-emphasize a range of frequencies in a bell-shaped region about a center frequency, a shelving filter is used to emphasize or de-emphasize all of the frequencies above or below a desired corner frequency.
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Page 18: Dither
IGURE dither • In order to understand dither, we must briefly discuss the problems associated with quantization and re-quantization. First, quantization is the process whereby a continuous- valued analog signal is converted into a discretely valued digital signal. In the case of compact disc digital audio, an audio signal is represented by 16-bit samples taken 44,100 times per second. - Page 19 40 bits, whereas the CD source material feeding it is only 16 bits. Ideally, we would like to present the digital-to-analog converter (DAC) with a signal having the proper bit-width. For today’s 20-bit converters, we need to somehow “map”...
- Page 20 The answer has to do with dither. Suppose you are playing a 16-bit CD through the rdq-6 and into a 20-bit DAC. With the volume set to 0.0 dB, the 16 bits of the CD are aligned with the 16...
- Page 21 (MSBs) of the DAC. Roughly speaking, attenuating the signal corresponds to “shifting the bits” to the right. Those against digital volume control would argue that the loss of resolution begins to happen when the least significant bit (LSB) of the CD data “slides”...
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Page 22: Appendix B: The Relationship Between Q And Slope
The relationship between slope and Q is fairly straightforward but requires a bit of preliminary explanation. Appendix A gives some background on the unique digital filter structure that the rdq-6 uses for its parametric equalizer filters. This structure leads to the lowest-noise, best–sounding digital filter possible. One of the few complications this structure imposes, however, is a limitation on the range of possible bandwidths that can be realized. -
Page 23: Appendix C: Finite Wordlength Digital Filtering
C: finite wordlength digital filtering Two of the primary challenges facing designers of digital filters are dealing with quantization error and dealing with roundoff noise. Quantization error refers to a digital filter’s sensitivity to coefficient quantization within a fixed-wordlength system, as occurs any time a real-world processor is used to implement the digital filter. - Page 24 Other filter architectures, such as the wave structure, the cascade structure, and the lattice-ladder structure arose in an attempt to make better filters.
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Page 25: Appendix D: Rdq-6 Automation Protocol
##h (where ## is the hexadecimal byte). • Automation Port Reconfiguration The port on the rear panel of the rdq-6 can be configured to accept either RS-232 signals or RS-422 signals. The rdq-6 comes configured for RS-422 signals from the factory due to the improved performance of the protocol. - Page 26 The table below describes the functions that the rdq-6 will perform. Function Function Word1 Word1 Word2 Word2 Main Volume Up (none) Main Volume Down (none) LF / Ch.1 Offset Up (none) LF / Ch.1 Offset Down...
- Page 27 The input change command (1Fh) switches the active inputs for the rdq-6. The following table shows the values for word2 for each combination of inputs. Word2 Word2 L/R Front L/R Front L/R Surround L/R Surround...
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Page 28: Specifications
• Inputs: 1 AES/EBU (transformer-isolated, 110-ohm terminated on XLR), 1 S/PDIF (transformer-isolated, 75-ohm terminated on RCA) for each of 3 processor cards • Outputs: 1 AES/EBU, 1 S/PDIF for each of 3 processor cards •... -
Page 29: Precautions
If the display is still active and audio is not passing through the unit, turn the power to the rdq-6 off for at least 1 minute. If audio is still not passing through the unit or the valid indicators are not on while the source material plays, the fuse that is located on the power supply closest to the back of the unit is at fault. -
Page 30: Warranty
In the event that your Z-Systems Audio Laboratories product requires warranty service, take the unit, along with its packing material and proof of purchase, to any authorized Z-Systems Audio Laboratories dealer. The dealer will take care of the repair. Direct shipments to the factory are not accepted without a return authorization number. -
Page 31: Contact Information
Systems has also released a two channel, 24 bit analog-to-digital convertor to allow our customers to bring in their analog sources into our tone control products. We also make a six channel, 24 bit digital to analog convertor to facilitate the home theater conversion process in a single chassis.