Aurex SY-Λ 90

Commentary

This is a stereo preamplifier developed by inheriting the technology of Aurex's double number series.

The SY-Λ 90 uses a newly developed slide volume in the volume section.
This volume is composed of copper foil patterns and copper terminals. In addition, the balance type copper foil pattern is adopted, the contact part is multi-terminal, and the grease is selected to improve the sound quality.
Since the slide volume pattern can be taken in parallel, it has a feature of preventing deterioration of sound quality due to current concentration in the pattern of general volume.

The muting switch is laid out in line with the slide volume, and the volume control is concentrated in one place.
When this muting is ON, the output will be 0 and the indicator will change from green to red. In addition, this muting is automatically activated when the power switch is turned ON and when switching between MM-MC, and the green indicator will blink. When the circuit stabilizes, muting is automatically turned OFF.

The equalizer amplifier is a 3-stage direct DC amplifier in which the second stage differential amplifier is also connected to the cascode bootstrap, in addition to the first stage differential amplifier in which the dual transistor is connected to the dual FET 2SK146, which is also used in the SY - Λ 88 II.
The dual FET and dual transistor have excellent thermal balance. Moreover, the cascode connection reduces the self-heating of the first and second stages. This reduces DC drift and realizes a simple DC amplifier. The cascode bootstrap connection improves the linearity of the second stage with a large amplitude. This reduces the distortion factor and greatly improves the distortion factor characteristics against the impedance change of the input signal source.
Since the gain switching method is adopted for MM/MC switching, operability is improved and sound quality degradation due to the decrease in the number of circuit contacts is avoided.

The flat amplifier has only 4 μ V of residual noise and is a low-noise DC-amplifier with a simple structure. In addition, the SEPP (Single Ended Push Pull) circuit with class A operation realizes low impedance, and the characteristics are not affected by the capacitance of the connection code.
The first stage differential amplifier and the second stage differential amplifier are connected by a single chip dual FET 2SK270A with stable temperature characteristics through a cascode bootstrap connection.

The tone control uses a simple CR type with the tone element separated from the amplifier.

A toroidal transformer and a low-noise zener diode are used in the power supply section, and a high-speed commutator with a small recovery time is used in parallel to achieve low noise and low impedance from low to high frequencies.

In addition to the high-performance elements developed for the SY-Λ 88 II, high-quality elements developed for the SY-Λ 90 are used at key points in the circuit. In particular, parallel connection is actively used to greatly reduce impedance. In addition, large-capacity power switches are used to achieve low impedance by using rectifiers, newly developed electrolytic capacitors, and various film capacitors in parallel. In addition, in order to improve the sound quality of capacitors, we are reducing impedance of the capacitors themselves, reducing contact between different metals, and preventing vibration.
The power supply circuit uses a newly developed electrolytic capacitor for power supply and a newly developed u Λ -II type Λ capacitor, and the equalizer amplifier uses the same copper foil styrene capacitor as the SY-Λ 88 II.

Equipped with a Rec selector, the recording source can be selected separately from the source being played.
There is also an independent Rec off switch that can be turned off to disconnect the deck connected to the Rec terminal. This prevents sound quality degradation due to the nonlinear component of input impedance that occurs when the power switch of the deck is turned off.
The selected source is identified by the indicator, the input is blue, and the recording is red.

Equipped with a smoke panel sealing pocket, you can hide a switch you don't usually use.

Model Rating

Type	Control amplifier
Input Sensitivity / Impedance	Phono MM : 2mV/47k Ω Phono MC : 0.2mV/100 Ω Tuner, DAD/Aux, Tape : 150mV/47k Ω
Total harmonic distortion factor	Phono MM : 0.002% (Rec out at 1 kHz, 10 V output) Phono MC : 0.002% (Rec out at 1 kHz, 10 V output) DAD/Aux : 0.002% (1 khz, 3 v output, pre-out)
Cross modulation distortion factor	DAD/Aux : 0.002% (1 khz, 3 v output, pre-out)
Signal-to-noise ratio (IHF-A Short circuit)	Phono MM:88dB Phono MC:70dB Aux:110dB
Frequency characteristic	Phono : RIAA deviation ± 0.2 dB (20 Hz to 20 kHz, Rec out) DAD/Aux : 10 Hz to 100 kHz + 0 -1dB
Maximum allowable input (1 kHz, THD 0.003%)	Phono MM:280mV Phono MC:28mV
Rated Output / Impedance	Rec out:150mV Pre out:1V
Maximum power output	Pre out:10V
Subsonic filter	MM, MC : 16 Hz, 6dB/oct.
Tone control	Bass : ± 8 dB (100 Hz) Treble : ± 8 dB (10 kHz)
Loudness	100Hz:+6dB 10kHz:+2dB
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	22W
External dimensions	Width 420x Height 84x Depth 369 mm
Weight	7.3kg