Analog disc playing has deeply improved on the present popular digital audio sources, and now along combined is an individual phono amp seeking more of a sound quality.Therefore the functions sought in the previous phono amp is consolidated to the signal source selection and volume adjustment. It is becoming to be the control center of the system.This time we made good use of the semi-conductor circuit technology, maintained Phase Tech’s developmental thoughts, and developed a 3series control amp CA-3 which expanded the ideal volume adjustment circuit which is the core technology introduced in CA-1.

      


Volume Adjustment Circuit Actualized With an Ideal Gain Control

The “hybrid gain control circuit” is introduced that was developed in the upper class model CA-1. For this circuit, an ideal gain control is made possible in order to prevent signal power losses sent from the source device due to the impedance matching theorem.As a result, the main unit’s volume adjustment circuit has enough volume resolution (46 levels) to actualize an absolute non-use of active elements, high input impedance and low output impedance. Even if the volume is dropped, the osmotic force is maintained and can be enjoyed having no sound diminishing.This unit uses an electric switch for gain switching but in order to prevent sound quality diminishing due to a cascade connection of the electronic switch, it is made up of a 48-step 1-phase attenuator although the scale becomes large.The electronic switch which is the gist is introduced with a factory analog multiplexer IC 10 times more of a high resistance pressure than the previous ones and guarantees enough dynamic range and linearity.

     


Amplifier Circuit Due to the Semiconductor Element

Our original FULL SYMMETRICAL NON-FEEDBACK CIRCUIT: TM evaluated in EA-3 is introduced into the amp for all steps.To aim for an enlargement of music expression, all steps are symmetrical non-feedback circuits due to electric current amplifying operations fit for the semiconductor. As a result, music play with full of excitement and a rich expression and plus a “gradational expression of rich sound, excitement and S/N feeling, and excelled open-air expression compatibility is accomplished which is possible only with a non-feedback circuit.

The first grade ones due to complementary FET (electric field effect transistor) connections, an extremely low noise voltage current conversion circuit is structured.Since operation points are decided due to self biased operations for strictly selected elements, biased circuits are unnecessary and there are no noises flowing in or sound quality deteriorations but the element’s original low noise operation of elements.

The first grade units carefully maintain the excellence in fast response having high sound quality and low GmGET and used selectively.

The second step structures an electric current amplification and a voltage conversion circuit and has a stable gain characteristic which is voltage-converted due to a high stable fixed resistor connected to the electric current output point and has stable transient characteristics even for very high frequency areas.For this circuit, various circuit techniques are included having high accurate performances without receiving any electric current conversion tolerances or parametric changes of amplified elements that are dependant on the output voltage. Although it is a non-feedback type amplifier, it has various excelled characteristics that makes it to be equal as a feedback type amplifier.

The output buffer circuit guarantees a high input impedance crossing over a wide area due to an input boost wrap and the output element with a Darlington connection holds enough electric amplification and at the same time drives the next connected device strongly.

The balance output reverse signal generation circuit is a non-feedback structure due to a 1-step conductance amp and unlike the reverse amps of the previous OP amps, it accomplishes an accurate reverse operation of a wide area without any punch-through phenomena. (note 2)
(note 2: a phenomenon where an input signal in phase with the same positive phase signal is outputted instantly when a fast signal without forming a negative feedback operation is inputted.)


A Simple Signal Transmission

The control amp was narrowed down to the necessary functions without passing through any redundant points but maintained the purity of the signals. Correspondences can be made if the DSP, etc. exterior sound quality adjustment device utilizes the EXT. PRO input/output circuit of this unit.The balance adjustment is done by offsetting the attenuation level of the LR of the “hybrid gain control circuit,” and omits redundant gain adjustment structures which is the cause of deterioration of the sound quality.”For a control amp with multiple source signals together, in order to maintain the signal purity, the input circuit design is important but by arranging the mechanical relay of the enclosed gas type for this unit, it will not accept the disturbances from others but accomplishes a simple signal transmission having no resonance, no vibration, and no interferences.


Dual monaural construction

From the power circuit, this equipment composes the symmetrical dual monaural construction completely and actualizes the advanced uniformity of the right and left channels. (The L and R are in common for the power transformer)This equipment supplies an ideal power without parameter changes from power loads due to the left/right independent power transformer and the shunt type local power supply. The channel separation with 90dB or more (20Hz-20KHz) has been achieved by minimizing the loop of the circuit current.

                        


Direct grounding construction of the power transformer

For this unit, in order to prevent sound quality deterioration due to the mutual interference via the analog circuit and control digital circuit power supplies, a specified transformer is used for each.These R-core type power supply transformers of this unit with a large core operates with extra space due to the magnetic flux density and reduces magnetic vibration and leakage of flux as much as possible.In addition, this transformer is assembled directly to the foot of carved high carbon-steel stick through the 5mm thick bakelite board that is an insulator with high electric/magnetic resistance. As a result, the vibration from which the power transformer generates is discharged into the earth at once without transmitting to the chassis.