Commentary
A control amplifier developed by Yamaha to commemorate the 100th anniversary of its founding.
We took seriously the wave of digitization, the wave of sound field reproduction, and the wave of, and the wave of high-quality visualization that cannot be achieved by looking at the other side of the shore, and created it by gathering together the highest level of electronics that Yamaha possesses.
A DEQ (Digital Parametric Equalizer) is installed as an acoustic compensation device.
This DEQ differs from the conventional multi-element GEQ in that there is no fluctuation in characteristics due to variations in elements, the three major elements of the EQ, i.e. center frequency, level, and Q (sharpness of Yamadani), can be precisely set, and accuracy and sound quality are not impaired by logic control or remote control.
This DEQ consists of three band parametric components : LOW band, MID band, and HIGH band. In addition, LOW cut filter and a HIGH cut filter.
The LOW band covers 20 Hz to 500 Hz, the HIGH band covers 2 kHz to 20 kHz, and the MID band covers 22 Hz to 18 kHz at maximum, which is between the center frequencies set for the LOW and HIGH bands, so as to cover both the LOW and HIGH bands.
In addition, the center frequency can be selected between 20 Hz and 20 kHz, 1/6 octave steps, or 61 points.
Each of the three bands can be adjusted to -12dB to + 6 dB in 0.1 dB steps. The Q range is from the standard 0.7 to the steeper 1.4, 3.0 and 6.0. You can change the equalization curve to broad or narrow.
Using only these three bands, there are approximately 8 trillion types of equalization curves that can be obtained by combining the center frequency, level, and Q. In addition, there are approximately 50000000000000000 types of equalization curves by adding slope characteristics (three stages), a 37-point LOW-cut filter with a cutoff frequency between 14 Hz and 900 Hz, and a 19-point HIGH-cut filter with a cutoff frequency between 1 kHz and 19 kHz. Thus, it is possible to drive as far as possible.
Also, by fixing the center frequency and Q, it can be used in the same way as normal bass / mid / treble tone control.
The internal operation is 32 bits and the dynamic range reaches approximately 200 dB, exceeding the maximum dynamic range of the human ear.
A DSP (Digital Soundfield Processor) is installed to correct the sound field.
It is equipped with key devices that realize omnisound, Yamaha's original CMOS type VLSI, and three digital sound processor DSP LSIs. For music signal data memory, six 256k bit DRAMs are directly connected to each DSP LSI to allocate a total of 18 DRAMs. The total memory capacity is 576k bytes.
In addition, a 256 kbit ROM is installed for the echo pattern memory of sound field spatial characteristics based on the reflected sound data actually measured at concert halls and churches. This memory contains three types of data : initial reflected sound data, initial reflected sound data + reverberation sound data, and reverberation sound data. In the case of initial reflected sound data, up to 22 pieces per channel, total of 88 pieces per 4 channels are stored.
These are prepared as a total of 16 programs from Hall 1 to Theater 3, and are read according to each program selection.
Parameter control is a total of 96 parameters, 6 parameters per program. You can freely arrange the sound field with delay control of 1 ms step and reverberation level adjustment of 1% step.
Taking advantage of the unique characteristics of digital control of DEQ and DSP, it is equipped with 16 sound memory functions which can store these characteristics arranged.
DEQ and DSP independent memories are available, as well as DEQ and DSP combined sound memories. You can easily recall the desired characteristics without readjusting each time you use it.
The Line 5 of CDs, DAT1, DAT2, VDP1 and VDP2 is equipped with 75 Ω coaxial pin jacks based on the digital audio interface format. The DAT1 and DAT2 are equipped with digital re-out and digital dubbing is also possible.
By installing an A/D converter, analog signals are also converted into digital signals, which can be digitally controlled through DEQ and DSP.
For the A/D conversion, a DAT-quality A/D converter with a sampling frequency of 48 kHz and a 16-bit linear quantization bit is installed. In addition, a dither circuit is also installed realize A/D conversion with good linearity.
The dither circuit superimposes on the sampled input signal a dither signal based on an established variable, which is correlated with the quantization step width, and subtracts the dither signal from the converted output signal. The dither circuit distributes the input signal, which can take various values, to the upper and lower quantization steps as an expected value.
This greatly reduces the quantization error.
This A/D converter uses Yamaha's original ADA LSI and has an LR-independent twin configuration.
The D/A converter is equipped with Yamaha's original high-bit digital filter.
It suppresses out-of-band noise and in-band ripple to less than 16-bit resolution, and eliminates county delay distortion by four times over sampling.
For the main signal, a high-bit D/A conversion system is installed to achieve higher accuracy.
This system is D/A conversion of 18-bit operation, and step distortion is reduced to 1/4.
This improves the conversion linearity for small signals.
The D/A converter itself uses a high-speed, glitch less D/A converter. Both the main signal, front presence signal and rear presence signal are LR-independent twin configuration.
For volume adjustment, in place of the conventional volume + amplifier, it is equipped with VCA which can obtain an arbitrary volume level by changing the gain of the amplifier itself.
The most important VCA amplifier is a single-chip IC composed of 64 ultra-low-noise transistors. Three VCA ICs are used per channel for VCA1 immediately after analog input, and one for VCA2 immediately before analog output.
The VCA control control method, the control voltage for the volume rotation angle is converted into a digital signal through an A/D converter, and the built-in microcomputer system reads the attenuation amount by referring to the data table and sends it to three VCAs, VCA1 and VCA2, and DEQ just after the digital input.
In addition, VCA1 and VCA2 have their own data tables, which convert digital signals into control voltages via a D/A converter to operate the VCAIC. The gain of VCA1 is + 20 to -6dB and that of VCA2 is -6 to ∞ dB.
As a result, not only the source from the analogin but also the source of the digital-in is controlled in a unified manner, and the volume itself can be controlled digitally with an analog sense.
As a matter of course, there will be no sliding noise, galling noise, or gang error seen in the previous volume.
Since the output level of the program source device is not constant, if input is made under the same conditions, the difference in sound volume will cause a hearing problem.
To solve this problem, the amplifier is equipped with an input level volume preset function so that the amplifier can fine-tune the signal level of each input source.
The input sensitivity can be set in the range of 0 to -6dB for a total of 11 inputs from CD to VCR2.
In order to prevent the occurrence of crosstalk due to the routing of internal wiring and the deterioration of transmission characteristics due to oxidation of contact points, an original 8-bit microcomputer controlled electronic switch using discrete transistors is adopted for each input / output switching of analog, digital and video. In addition to VCA, non-contact control from input to output is realized.
Since the sound quality of an amplifier without a mechanism is greatly affected by the material and structure of the cabinet / chassis, we are working to increase the rigidity of the cabinet / chassis.
The front panel is 9 mm thick, the top and bottom plates are 5 mm thick, and the rear panel is 3 mm thick. Non-magnetic extruded aluminum material is used for each.
In addition, in order to prevent high-frequency digital signals from jumping into analog circuits, we have adopted a 2-box chassis structure in which the analog section and digital section are divided into two sections, one above the other.
The center plate is made of 5 mm thick non-magnetic aluminum extruded material. The motherboard for analog section, digital board for digital section and DEQ / DSP board are fixed to the center plate with 10 mm diameter brass machined posts to prevent adverse effects of vibration.
In order to reduce the adverse effect of vibration on the analog circuit, a unit amplifier configuration is adopted in which the board is divided for each section of the analog circuit.
A total of 12 unit amplifier boards are divided into VCA1 (L/R), VCA2 (L/R, FL/FR, RL/RR), ロパスフィルタ (LR, F/R), and muting drive circuits. In addition, a unit housing made of non-magnetic extruded aluminum is prepared in order to prevent the invasion of external noise propagating in the space. The 12 unit amplifier boards are stored in 6 unit housings.
Four video input channels and two video output channels allow video cassette recorders to copy and edit each other. In addition, a monitor output for sending video signals and a video buffer are installed in the Rec Out.
Wireless remote control unit included.
The DEQ and DSP part of the digital control, the microcomputer controlled electronic switch for input / output switching and volume adjustment, and VCA do not involve control signals inside the signal line, so external control with high sound quality and high precision is possible.
In order to eliminate mutual interference through the power supply, the analog, digital and video sections are separated including the power supply circuit in a 3-transformer configuration.
Each transformer uses a large amount of an oriented core, with sufficient power supply capacity and low magnetic flux density to minimize leakage flux.
Furthermore, by filling the inside of the shield case with epoxy resin, harmful vibrations are suppressed.
A liquid crystal display with back light is used to display the DEQ and DSP components.
In the DEQ section, the center frequency, level and Q of the three bands are displayed numerically, and a triangular display is attached to the frequency scale. In the DSP section, each parameter including the program name can be displayed in alphabets and numerals.
Glass epoxy boards with excellent durability and temperature and humidity characteristics are used for each analog unit amplifier board, mother board, digital control board of digital section and digital processing board.
As a double-sided through hole, electrical characteristics are improved and part mounting reliability is improved.
The capacitor used for the power supply uses Chemicon for low magnification and high quality audio developed for the CX-10000.
In addition, high-quality parts such as copper foil Mylar capacitors are used in each circuit section.
All analog, digital and video input / output terminals use gold-plated brass machined pin jacks with excellent corrosion resistance and contact properties.
The AC power cord uses a 10 mm diameter cable made of OFC wire, and polarity is indicated on the power plug.
Equipped with a dedicated cable connection terminal that enables power on / off of the MX-10000 in conjunction with power on / off of the CX-10000.
A photocoupler, which is an optical coupling element, is used to transmit the power control signal to prevent degradation of sound quality.
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