SANSUI B-2103 MOS VINTAGE

Commentary

This is a stereo power amplifier that uses a MOS FET element and is designed to take advantage of its capabilities.

Equipped with an α -X balance circuit that provides a consistent balance operation from the source input to the speaker drive.
The output stage is a push-pull type of power MOS FET, and a total of four amplifiers equipped with both + - and left and right speakers are driven under the same conditions.
As a result, the amplifier circuit and ground circuit of the amplifier are completely separated, and the circuit itself shuts out the in-phase distortion caused by the back electromotive current and external noise generated in the speaker in principle.
In addition, the NFB adopts a unique balance feedback configuration that crosses from the + side output to the - side input and from the - side output to the + side input to achieve a wide range.

A power MOS FET, 2SK405/2SJ115 pair is used as the output element of the power stage.
This element has excellent linearity and enables stable high-speed amplification because no accumulation effect occurs.
In addition, the MOS FET has high quietness at a minute level, low distortion factor, low impedance, advanced α -X balance circuit, and power supply section to bring out the original sound quality of the MOS FET.

In order to cope with dynamic range such as digital source, cascade connection of FET is used for input, and NEW diamond differential circuit which can take out output of - side without phase inversion in power stage is adopted.
In combination with the driver power supply, it demonstrates excellent linearity, large current supply capability and high-speed response, and suppresses sound loss caused by TIM distortion.

In order to maximize the operation of MOS FET amplifier which requires stable large current, it is equipped with power supply of all stage independent power supply.
We pursue low impedance and high speed and obtain stable current by using high performance electrolytic electrolytic capacitor and fast recovery diode as well as a vibration control structure and low leakage transformer originally developed for B-2103 only.
In addition, a closed-loop balanced configuration is adopted in which each stage is an independent power supply and the final power supply is separated from the ground circuit to prevent sound quality degradation due to unbalanced power supply and natural vibration and noise of the power supply.

In order to eliminate the influence of vibration of the power supply and signal system, which is an obstacle to stereo reproduction, the power supply is placed in the center of the amplifier and the power units are arranged symmetrically using twin monaural construction.
By optimizing the weight balance of the structure, the generation and transmission of vibration of the power transformer and condenser are controlled. Moreover, by realizing the shortest circuit, sound image localization and phase characteristics are improved.

In order to further control the natural and external vibrations of the amplifier, an integrated mechanical feedback system is introduced.
For example, a MOS FET is sandwiched between pure copper plates, and pure copper is used for transformers, bottom plates, insulators, and other parts.
In addition, a Teflon sheet is used to isolate between the bottom plate and the insulator to cut off the transmission of vibration and maintain the purity of the music signal.

Parts that determine sound quality are gold-plated, non-magnetic, low-impedance, high-speed, and vibration-proof.
The connectors include RCA gold plated terminals made by WBT, Germany, which have low impedance and excellent corrosion resistance, as well as gold plated balance input terminals made by Neutrik, gold plated resistance (RMG), gold plated film capacitors (GUG), OFC lead butyl capacitors, and silmic electrolytic capacitors (ARSA).

For the front panel, which is the face of the amplifier, a 6 mm thick aluminum plate is embossed in consideration of vibration resistance.
In addition, the side panel with 8 mm thick felt inside, which absorbs unwanted reflected sound, and the chassis with the top plate made of aluminum provide a stable structure.
The bottom plate is a double bottom made of pure copper and copper-plated chassis, and a newly developed oval pure copper solid insulator made of teflon sheet and felt is installed.
While utilizing the internal loss of pure copper, it disperses vibration and resonance and completely eliminates internal interference and external vibration.

Model Rating

Type	Stereo power amplifier
Effective Output (10 Hz to 20 kHz, Simultaneous Operation for Both Channels)	150W + 150W (6 Ω) 110W + 110W (8 Ω)
Total harmonic distortion factor (at effective output)	0.008% (8 Ω)
Cross modulation distortion factor	0.008% (8 Ω)
Damping factor	200 (8 Ω)
Frequency Response (1W)	DC ~ 300 kHz, + 0 -3dB
Input Sensitivity / Input Impedance (1 kHz)	1V/10k Ω
Signal-to-noise ratio (A network)	110 dB or more
Dynamic Power	190W (6 Ω) 240W (4 Ω) 320W (2 Ω)
Envelope distortion	Below the measurement limit
TIM Strain (STRAIN)	Below the measurement limit
Slew rate	150 V / μ sec
Rise time	0.5 μ sec
Channel Separation (1 kHz)	90 dB or more
Subsonic filter	10 Hz (-3dB), 6dB/oct.
Load impedance	4 Ω ~ 16 Ω
Pwer	100 VAC, 50Hz/60Hz
Rated power consumption	350W
External dimensions	Width 450x Height 173x Depth 477 mm
Weight	35.0kg