No feedback single output circuit adoption of 1 transistor

DA converter unit YDA-01

In order to solve the hardness of the sound of CD player

Conventionally, our company put power into analog record playbacks, such as manufacture of an analog cartridge, and development of phono equalizer amplifier, and has carried out product development. However, the public center is CD and cannot deny it. Generally, each public CD player has a hard sound, and there is a tendency for grace to be missing. Then, it decided to manufacture a DA converter lately, making full use of the know-how of the amplifier design which our company has cultivated over 15 years. Some trial productions have shown that the output circuit of a DA converter, IV converter and an output circuit, has influenced sound most. Usually, the output circuit of the operational amplifier system used widely has a hard sound, although the characteristic is excellent, and it has also turned out that grace is missing. The circuit of an operational amplifier system has very many elements to pass, and the merit of the characteristic is brought about by a lot of feedbacks. Our company is the completely opposite composition of the amplification circuit by two vacuum tubes adopted with the tube amp. A lot of feedbacks are also worried. In the tube amp, I realize that feedback of mere a few hardens sound and reduces the charm of sound by half. Then, inevitably, when this circuit composition was made simpler, I thought that sound would become more natural.

The no feedback single output circuit with one transistor for the output stage.

The output side of DA converter adoption usual as a current output. DA converter IC and PCM1794A which are used for this machine are also a current output of the operation circuit. Therefore, it is necessary to change it into a general voltage output. Moreover, the operation output needs to compound it and needs to change it into one output. For that purpose, a total of three amplifier is needed, and circuit composition becomes very complicated. Since an analog filter is generally also incorporated in the circuit, it cannot but become still more complicated. At our company, it thought that the cause of the hardness of the sound of a DA converter would be in this portion, and the design of the DA converter was begun with the design plan to make these output circuits as simple as possible. As a result, the adopted circuit was an output circuit of the common base with one transistor, and the no feedback single system. It resulted in the conclusion that sound quality is excellent, so that there were few elements which a circuit is simple and are passed. Although the output circuit by the vacuum tube made for us. to be its favorite was also examined, since it became quite complicated, adoption was given up this time. The adopted circuit pours the current output from a DA converter into the emitter of a PNP transistor. It is the very simple composition of changing a current output into voltage only by one transistor and one resistor by the system of changing it into voltage by a collector's load resistor, and also serving also as an output circuit as it is. Although we have adopted the primary analog filter as the output unit, it is a simple circuit which does not have more than this in circuit. The differential output unit of PCM1794A uses only one side, and the remaining one side is not using it only for it being to unite load conditions carrying out. It decided to use the type of entering metal casing transistor with the most sufficient sound to be used by repeated audition. Sound quality became very natural by this circuit, and freshness became the sound highly filled with a feeling of a lively motion.

PCM1794A is used for DA converter IC in two monophonic modes.

By using L channel and R channels at a time for DA converter IC of a realization the YDA-1 for the newest highly efficient PCM1794A in monophonic mode, respectively, it is powerful, and the highest performance is considered so that there may be no interference between channels. Although PCM1794A has a large value of output current and at least one sufficient level is obtained, the more nearly energetic sound has been obtained by making it the Parallel connection.

By supplying the power supply of each IC from a respectively individual regulator circuit, the interference to the circuit by a power supply was eliminated.

IC currently used for the DA converter has a digital circuit and analog circuitry inside, respectively. Therefore, those power supply supply terminals are divided. Although the portion is supplied in a common DA converter in one piece or two power supply circuits, in each circuit, it is possible that the leak of the noise which leads, etc. produce those power supplies, and performance is influenced. Furthermore, a power supply is supplied through a long distance by the pattern of a thin and small printed circuit board. Although power supply impedance goes up by it, the present condition is having stopped and deceived it with many bypass capacitors. In this machine, by arranging to the nearness of each IC, a regulator circuit board suppresses the rise of the impedance of a power supply line, reduces the number of bypass capacitors, and lessens influence on the sound quality by capacitors. The regulator circuit which became independent for every circuits of those was prepared, and it succeeded in losing most interference for every circuit which led the power supply. In YDA-01, three pieces of regulators were adopted to digital prosessor and four pieces were for DA converter circuit, two regulators were adopted as the output circuit , and it has taken all possible measures against circuit.

Adopt a mass troydal transformer as a power transformer, the winding the object for analogs and for digital one is made to become independent, and a mutual interference is suppressed.

　The power transformer currently used for this machine was excellent in instantaneous power, and has adopted the troydal transformer which responds to a digital quick signal change easily. The transformer supports the powerful sound of this machine by capacity of usual 5 times or more called 150VA.

The ring core of form which dropped the angle called the Max ring on the core material is used, there is very little disclosure magnetic flux and electromagnetism efficiency is very excellent. The source of the forcibleness of what kind of audio instrument or its sound quality is a power supply circuit, and the influence does not change with a DA converter, either. The sound is also weak and the poor amplifier of a power supply part serves as a weak-looking sound. This transformer made the digital part, the analog part, and the object for output circuits become independent, respectively, was made to become independent, and has prevented a mutual interference. Moreover, reliability has adopted as wiring material the Teflon insulation and the silver plating copper wire which are very highly excellent also in sound quality. Since these wiring material has the performance according to MIL specifications and standards, durability, the aging characteristic, etc. have the highest characteristic.

CS8416 was adopted as digital processor IC and it corresponded to the incoming signal of the large range.

　CS8416 which has established reputation in digital processor IC of this machine is adopted, and the incoming signal of the large range up to 32kHz - 192kHz is corresponded and followed automatically.

Moreover, the input unit dares to reduce a circuit and is aiming at stabilization of performance as an input of only one same axle type circuit. Moreover, the analog output part also held down cost only as one circuit by RCA, and the product excellent in cost performance was aimed at.

The high quality part was used for the use part with the tone quality priority.

The part that is using it for this machine is using the high quality part that was sorted by the test listenning with the analogue department, digital department, power supply circuit. The mica capacitor, OS Con etc. made of the both sides trust electricity are being used for the checkpoint to the capacitor including the polypropylene film capacitor. The resistor and the like select the high capacity, surface SMT resistor of the U.S. DALE company by the test listenning and be using. Also we insert the output capacitor to the case made of the ebony and be doing the tone quality measure. The neighbour bronze shaving made by own company for the input-output terminal and used highly efficient pin Jacques of the Teflon insulation. It is not using it because the problem of the contact resistor and passing year change easy to come out and even the demerit on the tone quality is big although the connector and the like are used a lot in these digital circuits generally.

I prepare a kit version and reply also to a demand of a my original work group's person.

This machine also prepares a kit version besides finished goods, and it is constituted so that the pleasure which his original work group's user's person makes can be obtained. When a DA converter was made on one's own, it was making itself difficultly by becoming a neck that it is hard to treat IC of a digital portion very small itself. Incidentally an outside is distance between pins 0.65mm in 10.5mmx5.6mm by the type by which the package of PCM1794A is called SSOP. In the KIT version, a complicated and precise digital portion is made into the completed form, and it is considered so that it may assemble also to whom simply and can do. Since the digital portion and the output circuit portion are separated in this machine, it is also possible to make an output circuit on one's own and to constitute an original DA converter. Since the winding which 100V-0-100V 60mA for those who constitute the output circuit of a vacuum tube type became independent of is prepared, it can use for convenience. Moreover, I am also preparing the output circuit circuit board which uses highly efficient IC and OPA627AP at a time for each three channels as an option. In the output circuit board of an operational amplifier type, it is attached in the socket so that output IC can be exchanged. Moreover, the analog filter is devised so that it may attach arbitrarily or can remove. Probably, as an object for a its original work maniac's experiment, it is found useful very much. (All kit with parts and 1-set yen20,000)

YDA-01 Standard

Digital input terminal : The one same axle (RCA) Analog output terminal: one pair of coaxial (RCA) Output level:3.1V/0dB

Frequency:corresponding 32kHz to 192kHz (automatic) 8 time oversampling digital filter Frequency characteristic: 20-20kHz(±1dB)

Signal to noise ratio: 86dB (IHF-A wait) Output impedance : 2.6k ohms Outside dimension: 420(W)290(D)94(H) Weight: 5.2kg