Phasemation EA-320 Phono Stage



Non-feedback amplifier circuit manufactured by all discrete parts for all steps

The load feedback amplifier which holds the popularity of present amplifiers always compares the input and output signals and this difference (supplement signal) is amplified as an input signal which makes it possible for a high quality of amplification at a low cost.

In regards to this, non-feedback amps amplify the input signal itself, which makes a big difference.

However for a non-feedback amplifier, it does not have a supplemental operation as like the load feedback amplifier and therefore there is a rise in costs due to structural parts and requests high accuracy on the operation settings. However, in terms of sound quality, it is excellent in music impression, dynamics, and shading expressions and it is an amplifying type having strong support of music and audio funs and all Phasemation amplifiers adopt this non-feedback amplifying circuit.

For this equipment, a non-feedback amplifier circuit for all steps which might be only one in this class is adopted so that the circuit structure composed of well-selected discrete parts can operate ideally.

As a result, “rich gradational expression of sound, impression and high S/N, and excelled air expression coping” is reached at a high level, equivalent to an upper class device which was difficult on phono amplifiers of this class.

Substantial Functions

1,Two systems for input can be connected; and two arms can be connected.

2,Low Cut SW (20Hz): Prevents swing of speaker (woofer) for a bent record

3,Stereo/Monaural playing curve switch RIAA playing curve for Stereo, DECCA (UK) for MONO1 and COLUMBIA (USA) for MONO2

Accomplishment of Solid chassis and Dual monaural pattern

Because the fine weak signal of phono amplifier has to be protected, a solid chassis structure not to be influenced from others and a simple signal transmission are required.

a) Solid chassis structure

1) For the chassis base and top cover making of a 1.6 mm steel plate, copper plating and finishing are conducted. It achieved reduction of magnetic distortion and secured the high strength of rigidity. The front panel and top cover are made of aluminum; furthermore, for the front panel 10mm thickness board is used.

2) Mechanical earth/Direct grounding construction of power supply transformer
Magnetic vibration and generation of leakage flux is reduced as much as possible, because the R-core type power supply transformer operates with the margin made by low magnetic flux density.
In addition, this transformer is assembled directly to the foot to be cut from steel material through the 5mm thickness bakelite board that is an insulator having high electric and magnetic resistances. As a result, the vibration that the power transformer originates is discharged into the earth at once without transmitting to the chassis.

b) Dual monaural pattern

1) It builds the dual monaural layout of the same pattern of the left and right, and actualizes a uniformity of the left and right channels at a high level.

2) It supplies an ideal power without the parameter change due to the power supply load by right and left independent power supply transformer and shunt type local power supply. The channel separation over 100dB (20Hz to 20kHz) has been achieved by minimizing the loop of the circuit electric current.

Introduction of High Quality Parts

The following evaluated high sound quality parts are adopted for the RIAA impedance elements and the audio signal main portion which strongly influence a sound quality of a phono amplifier.

1) Metal film resistors with some margin of the rated value
2) Parts having high sound quality such as a high quality film capacitor

The following parts are adopted for the power circuit in order to prevent the decrease in speed of recovery in high current range, which has made it structure a very low noise power supply.

1) Newly adopting SiC diode made by ROHM which is evaluated as high sound quality because of small switching noise
2) Low noise Zener diodes for composing of extremely low noise power supply


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