Audio Database


250,000yen(around the 1991 time)

It is a reference AV preamplifier of composition of having become independent about the image part and the voice part.

In DA-P7000, AV separate structure which dedicated the circuit of a video selector part and an audio part to another case, respectively is adopted. This has eliminated interference of a noise etc.
The control signal is supplied to the video part through the power-source line and photo-coupler of video system independent winding wire transformer adoption from the audio part. From this signal line, it has become [ that the signal for controlling necessary minimum current and video selector is sent, and ], and the perfect isolation of an audio part and a video part is realized.

The discrete composition which used the broadband high frequency transistor is adopted as a video amplifier part. Use and the interval of the switch only for video have realized a 20MHz broadband.

Bipolar switch IC only for video is adopted as all the selector circuits. Since a bipolar switch consists of emitter followers in which a switch part has a low Output load impedance and the broadband characteristic, the good switch engine performance is obtained to a video signal.

In order to prevent Y signal and C signal carrying out a mutual intervention, only Y signal selector part of the signal-processing circuit was constituted from an another board, and the solid board structure of uprighting this on C signal selector board so that it may become the shortest wiring distance is adopted.
It has been arranged by the curtate distance by this, without Y signal and C signal crossing, and improvement in many characteristics is realized.

Y/C separation circuit expert DCF is carried.
This circuit calculates the perpendicular and horizontal non-correlating energy of a picture signal per pixel, and develops and IC-izes the original algorithm which chooses three kinds of optimal filters (BPF). When it is not a level band pass filter (one dimension), either, when horizontal correlation is strong, and correlation is perpendicularly strong and it is not a perpendicular band pass filter (two dimensions) and which, either, Y/C separation is carried out with a slanting band pass filter (one-dimensional two-dimensional +).
This is reducing level and perpendicular dot disturbance and color Darre sharply compared with the conventional thing.

The same positive/negative 2 power-source composition as an audio circuit is adopted as a video circuit. By separating a power supply circuit and a grand circuit, inflow of the unnecessary circuit current to a grand circuit was reduced sharply, and high S/N-ization is realized.
Furthermore, by having adopted this composition, the coupling capacitor of an input and an output could be removed and high definition-ization is realized.

Full digital speech signal processing is adopted as an audio part. For this reason, it is processed with a digital signal until digital conversion is carried out, analog conversion is finally carried out and it also once outputs the signal inputted analogically by an A/D converter.

newly developed variable current - which pulled out the original merit of 1-bit type in the D/A conversion part -- discrete -- 1 bit of DAC are adopted.
In this DA converter, the constant current type PWM system which loses the power-supply-voltage change itself is adopted by carrying out the constant current drive of the electronic switch so that a circuit may not be influenced by power source variation, and also fixed-izing the load current of a power source. Moreover, the coupling capacitor is banished, having used the op amplifier for audios excellent in power-source-variation exclusion capability (made by U.S. PMI) for differential amplifier, or current / voltage conversion circuit, and having applied direct-current servo. This eliminates AM abnormal-conditions distortion and the merit of the linearity is pulled out to the maximum extent.

Digital volume is adopted as a volume circuit.
This volume can be made to carry out variable [ of the current value of the current generator of a differential switch ] in a volume controlling circuit, and has the structure where the rotary encoder interlocked with the volume knob detects rotation of a knob. Thereby, bit omission does not occur in any volume values from 0dB to -72dB.

In order to remove a Jitter and to prevent degradation of sound quality, the Jitter free digital sound collector is employed as a Jitter removal circuit.
This circuit has dual PLL composition which consists of two PLL circuits, 1st and 2nd. Moreover, it had the frequency accuracy and stability which are equal to crystal in 2nd PLL, and the variable width of frequency has adopted as it conventionally 3 or more times and the newly developed broadband LT oscillator which attained ±3,000 ppm or more.
It restores to a digital input signal with the clock which 1st PLL made first, and data is written in the memory buffer for 3 words by exclusive IC. And 2nd PLL applies a re-synchronization to the clock of 1st PLL, and generates a highly precise clock with few Jitters. The data written in the buffer with this clock was read, and the Jitter is banished.
Moreover, the Jitter removal effect goes up, so that the response of 2nd PLL is slow, in order that the oscillator in a loop may pursue a Jitter and may make a clock with many Jitters, if a PLL circuit has a quick response. However, if it answers not much late, it will become easy to separate from a lock, and the problem on which sound breaks off arises. Then, the stable lock is secured by carrying out the response of "2nd PLL" to an automatic two-step gear, and switching "high and low" according to a situation. Moreover, the super-low-speed response of PLL is attained.
To the power source of a PLL circuit, the independent shunt regulator is supplied for every block, and generating of the Jitter by inflow of a power-source noise is suppressed to it.

The digital audio signal with which processing of surround processing etc. was performed by DSP became the ripple which became dirty by the noise from the transmission process, and ID interface is adopted in order to prevent sound quality degradation occurring.
ID interface has the structure of transmitting only the information whether it is the high or low includeded in the signal instead of the digital signal itself. This is constituted by two C-MOS FET analog switches, and when one of the two is ON, it is already connected to the power source at one of the two in the ground. These power sources and a ground are maintaining the clean state with few noises. If a digital audio signal is not inputted into a D/A converter as it is here but it is made to act as a switching signal of two analog switches, at the time of a high signal, the switch of a grand side will be controlled for the switch of a power-source side by ON, respectively at the time of a low signal. Although the Hy Law relation of the digital signal newly made by this supports the incoming signal, the uncorrelated noise of the digital audio signal was shut out and has realized clean D/A conversion.

As surround mode, MHT logic and mono-logic other than the Dolby prologic are supported.
MHT logic is in original surround mode of Mitsubishi which was encoded by Dolby surround and which corresponds soft. The bit lack accompanying [ full digital processing is carried out and ] it by DSP corresponds by carrying out all the channel noise shaping, and the acoustic field effect has realized the high-definition surround play.

The center mode can choose REAL mode and VIRTUAL mode.
REAL mode is the mode set up when using a center speaker, and outputs all the zones from low-pass to a high region to a center speaker. Moreover, VIRTUAL mode is the mode set up when not using a center speaker, and orientates words etc. in the center by the speaker of two LR(s) by a directivity emphasis circuit.
Furthermore, it is possible to improve the center normal position by adjusting the attainment time of the signal of a center channel by C(CENTER) PRESENCE function.

In a MULTI DELAY function, the surround acoustic field same with having arranged 6-12 rear speakers in the large room can be obtained using 2-4 rear speakers. The width of an acoustic field can be adjusted by switching the mode.

The DELAY time of a rear speaker can be adjusted in REAR DELAY.
Moreover, in REAR FILTER, the barrier property of the low pass filter which cuts the upper register of a rear channel signal can be adjusted. It is usually set as 7kHz, and 4kHz is used to expand a feeling of an acoustic field for using 9kHz at a mild feeling of an acoustic field.

In THEATER LPF, the sauce which emphasized upper register to the movie theater play, and was recorded on it can be adjusted.

In an AZIMUTH function, when the angle (azimuth) of the playback head has shifted to the recording head in the soft work process, gap of a soft azimuth can be adjusted.

In an AUTO INPUT function, the state where a voice like the words which can be heard from a center can be leaked and heard from speakers other than a center channel is improved.

The subWoofer output is carried. The change of the three-stage of 40Hz in all/63 Hz/80 Hz is possible in the characteristic by digital processing in a low pass filter. The barrier property serves as 24 dB/oct.

In mono-logic mode, a feeling of surround is added to the video software and LD software of monophonic recording, and it can play.

The ounce clean function in which adjustment of surround audio mode, dubbing processing, etc. can be performed while checking on a screen is carried.
The display is three kinds of the sub screen which opts for the volume of each [ a main screen and ] speaker and ON/OFF of a subWoofer which can choose the sauce of input and output, the kind of surround, etc., and the REC monitoring screen which checks the state of recording and recording.
The display of a up to [ the blue back black back besides a superimposition ] is also possible.

The Ambi Sonique surround system in which the UK Nimbus has a license is carried.
Even if it reproduces usual stereo sauce, a feeling of surround is obtained, but this surround system will demonstrate an effect, especially if the software encoded by the Ambi Sonique system is reproduced by four channels.

A push on a button will attach the wireless remote control which carries the writing function in which a display shines.
the auto function function in which even a button comes out and a series of operations of the system which consisted of AV equipment corresponding to an auto function can be performed with Mitsubishi products is carried in this remote control. Moreover, the function of other AV equipment of remote control is learned, and the learning function which can be operated is also carried.

Image Attached
Input Toroidal Use
Y/C Digital Copper-coating

Rating of a mode
Form Multichannel control amplifier
Digital input Optical: Five lines
Coaxial: Four lines
Digital output Optical: Two lines
Coaxial: Two lines
Analog terminal Analog input: Ten lines
Analog output: Five lines
Preamplifier part output Front 2ch, center 2ch, subWoofer 2ch, rear 4ch
Acoustic field control (digital) Dolby ProLogic
MHT Logic
Mono Logic
Power consumption 72W
Dimensions Audio part: Width 425x height 132x depth of 464mm
Video part: Width 425x height 87x depth of 393mm
Weight 18kg
Attachment Wireless remote control