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日本Phasemation(协同电子) EA-300 MC/MM晶体管式唱头放大器

phasemationEA-300pic01

 

日本Phasemation以前型号EA-3II作基础设计,选用全新设计的电源变压器,以增强供电的精确度及进一步减低变压器对唱放带来的干扰。EA-300采用无回输电路设计,每级放大线路都使用独立原件。

 


 由于负回输电路都是以输出量值与输入作比较,以计算差距来作修正或限流,这种较低成本之处理方案。相反,无回输电路设计是没有依靠这样的修正以作为一种保护电路。这样整体的放大线路就需要考虑使用更高级的原件来处理。而每段电路设计上,便要求有更精密的计算,以免出错导致放大或传讯产生误差!


 
 
拥有极高讯噪比的EA-300,亦采纳Phasemation一向坚持的Mechanical Grounding (机械接地)避震方式,令已经是相当高质量的"R型线圈牛"工作更稳定之余,还营造出更低的漏磁作用,加上达5豪米厚的钢材底垫和1.6豪米厚的底盘,令"火牛"所产生的谐震不会回传至机体内。EA-300唱放亦秉承过往设计,采用左/右独立声道全对称式电子底板设计,以两枚"R-Core火牛"作独立供电,大大提高隔离度和干扰,使声音的分隔度带来超越100dB的理想效果!


 
 
RIAA均衡放大电路上,"协同"选用了金属膜电阻、SiC二极管和聚炳稀膜电容等多款组件,务求将此段在唱放最关键的线路上做到+/-0.3dB的极微典线误差,来还原黑胶讯号。
 


 EA-300功能上,设有Low Cut SW (20Hz以下)旁路功能以减低单原音盆的损害性。立体声及单声道回放的均衡曲线选择,包括标准RIAA以回放立体声,英国Decca曲线回放单声道及Columbia单声道回放曲线三项。两组可切换RCA输入及一组输出。而增益方面,MC输入以0.12mV灵敏度下可达65dBMM输入为38dBMC输入阻值为470Ω

 

 

 

主要特点 Main Feature

 

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

 

 

 

获得奖项 Received Prizes

Audio Excellence Award 2015 Bronze Prize

 

 


 

 

技术参数

Form

Equalizing amplifier featuring V-I/I-V conversion and non-feedback for all stages

Input Type (Cartridge)

MM

MC

Input Sensitivity

2.5 mV

0.18 mV

Output Impedance for the Cartridge

47 k-ohm or less

1.5 to 40 ohm

Gain

38 dB

61 dB

Input Equivalent S/N Ratio

–120dBV

–140dBV

Rated Output Voltage

200 mV (1kHz)

RIAA Curve Deviation

± 0.5 dB (20Hz to 20kHz)

Power Consumption

12W (100VAC, 50 to 60Hz)

Dimensions (mm)

210(w) x 103(h) x 355(d)

Weight

5.5kg for each channel unit

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