Accuphase DG-28
¥ 530,000 (released in May 1997)
Commentary
Digital voice equalizer using advanced digital signal processing technology unique to ACPHASE.
The DG-28 integrates the two functions of voice measurement and correction by utilizing digital signal processing technology.
Analog methods suffer from aging degradation, temperature dependence, circuit constant accuracy limitations, and degradation of characteristics when adjusting sound quality, which are unique to analog circuits. Digital methods solve these problems.
In addition, digital signals are noise-resistant and suitable for signal processing to control frequencies such as tone adjustment and filters. Therefore, the DG-28 adopts a digital system using an ultra-high-speed DSP (Digital Signal Processor) from input to output. The resolution of this DSP is 24 bits for input and output, and internal processing is 48 bits. This ultra-high-speed DSP with one operation of 40 ns is equipped with two DSPs per channel and four DSPs for both sides.
The filter cell, the heart of the equalizer, determines various characteristics such as the center frequency of each band and the range of variable levels. On the DG-28, 64 filter cells are combined into one channel, which is called a filter engine. The filter engines are installed on the left and right channels, and the filter cells are connected in parallel.
The parallel configuration not only eliminates calculation errors, but also reduces noise by canceling out the errors. The DG-28 uses AccuPhase's unique filter algorithm that operates a large-scale filter by tightly coupling multiple DSP chips. By separating unused filter cells, signal degradation due to calculation errors caused by unnecessary filter calculations is suppressed.
High-precision adjustment from 16 Hz to 22 kHz is possible with 64 bands of 1/6 octave band, and 32 bands of 1/3 octave band can also be selected.
The variable range of each band is ± 12 dB and can be adjusted with a resolution of 0.5 dB.
AccuPhase's unique ultra jitter-free PLL circuit is used for the PLL circuit that extracts the master clock for the system from the input DAI (Digital Audio Interface) signal.
This circuit uses a preamble signal (a marker indicating the beginning of the LR signal) detection circuit and a crystal oscillator for the VCO. The master clock extracted by this circuit is not affected by jitter or pulse transmission distortion.
A 320x240 dot LCD panel is used for the display. Graphical adjustments can be made while checking the 64-band compensation status and sound measurement information. In addition, the display can be turned off and the contrast can be adjusted, and the beep sound can be turned ON/OFF to confirm the switch operation with your ear.
The screen consists of three modes. You can switch between the equalizer mode, environment setting mode and analyzer mode with the MODE switch.
Equipped with a digital tone generator and analyzer function.
When measuring sound, the input of the filter engine is switched to the tone generator side, the signal for measurement is output through the filter engine, amplified by the power amplifier and driven by the speaker. The signal that has passed through the sound field space is picked up by the attached microphone and input to the analyzer of the DG-28, making accurate sound field correction possible.
The sound field measurement method employs a method in which a warble tone (signal with frequency changed in a narrow range) generated by a tone generator is swept over the entire frequency band. This measurement method is resistant to external noise and enables accurate measurement in a short time. The tone generator and analyzer are digital methods using DSP, so accurate measurement with excellent stability and reproducibility is possible.
It has a built-in automatic correction function that incorporates Acuphase's own correction algorithm.
The time required for automatic correction is approximately five and a half minutes for both channels. It is also possible to improve the correction accuracy through averaging by performing multiple measurements.
In general, when the transmission characteristics are made flat at the listening point, the energy in the upper range of the auditory sense becomes dominant and sound can be heard. Therefore, it is common to make the high range of the sound with the gradual lowering characteristic.
The DG-28 has a flat characteristic and can roll off at -1dB/oct, -2dB/oct, or -3dB/oct at frequencies of 2 kHz or higher. You can also draw an Edit characteristic.
If you want to add a finer correction after automatic correction, you can make fine adjustments while measuring for each 1/6 octave band.
Manual adjustment is also available.
It is also equipped with a function for measuring sound fields without correction.
You can save up to four types of corrected characteristics by selecting any program button.
A 1/4-inch back-electret condenser microphone AM-28 is included as a microphone for measurement.
The DG-28 is a full-digital-signal-processing voising equalizer. However, by adding an optional board (sold separately), you can control analog inputs and outputs in the same way as a conventional graphic equalizer. The DG-28 also has an optional board for digital functions, which can be added depending on the application.
Up to four option boards can be installed.
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Model Rating
| Type | Digital voicing equalizer | ||||||||||||||||||||||||||||
| Format | Digital 1/6 octave 64-band type (Switchable from 1/3 octave 32 bands) |
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| Center frequency | 64/32 point (16 Hz to 22.4 kHz, ISO standard) | ||||||||||||||||||||||||||||
| Q (Peak Sharpness) | 1/6 octave : 8.65 1/3 octave : 4.32 |
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| Frequency characteristic | 0 ~ 22.4 kHz ± 0 dB (Sampling Frequency : 48 kHz) | ||||||||||||||||||||||||||||
| Gain | 0 ~ -18dB Variable | ||||||||||||||||||||||||||||
| <Digital Input> | |||||||||||||||||||||||||||||
| Formatting | EIAJ CP-1201 Digital Audio Interface |
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| Number of quantization bits | 16-24-bit straight line | ||||||||||||||||||||||||||||
| Sampling frequency | 32 khz, 44.1 khz, 48 khz (auto-detect) | ||||||||||||||||||||||||||||
| Optical input level | Optical input, -27 to -15dBm | ||||||||||||||||||||||||||||
| Coaxial input level | 0.5Vp-p/75 Ω | ||||||||||||||||||||||||||||
| Digital Output | |||||||||||||||||||||||||||||
| Formatting | EIAJ CP-1201 Digital Audio Interface |
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| Number of quantization bits | 24-bit straight line | ||||||||||||||||||||||||||||
| Sampling frequency | Synchronous with input signal | ||||||||||||||||||||||||||||
| Optical output level | Light output (emission wavelength of 660 nm), -21 to -15dBm | ||||||||||||||||||||||||||||
| Coaxial output level | 0.5Vp-p/75 Ω | ||||||||||||||||||||||||||||
| <Others> | |||||||||||||||||||||||||||||
| Power supply voltage | 100 VAC, 50Hz/60Hz | ||||||||||||||||||||||||||||
| Power consumption | 12W | ||||||||||||||||||||||||||||
| Maximum external dimensions | Width 475x Height 150x Depth 393 mm | ||||||||||||||||||||||||||||
| Weight | 13kg | ||||||||||||||||||||||||||||
| Attachment | Microphone (AM-28) Microphone cord (5m) Microphone holder 75 Ω coaxial cable (2 pieces) AC power cord |
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| Attachment : Remote Commander RC-21 | |||||||||||||||||||||||||||||
| Remote control system | Infrared pulse system | ||||||||||||||||||||||||||||
| Pwer | Uses 2 DC3V / AA Dry Battery (AA/R6) | ||||||||||||||||||||||||||||
| Maximum external dimensions | 45 mm wide x 18 mm high x 136 mm deep | ||||||||||||||||||||||||||||
| Weight | 85g (including battery) | ||||||||||||||||||||||||||||
| Optional Board Sold Separately | |||||||||||||||||||||||||||||
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