Aurex SB-420

Commentary

Pre-main amplifier with various functions.

The RIAA element of the equalizer amplifier section uses a high-precision metal film resistor and capacitor to keep the equalizer curve within ± 0.3 dB. The circuit structure is a 3-stage direct-coupled circuit including one differential stage. By applying a high voltage of ± 40 V, an input resistance of 350 mV is obtained.

The main amplifier section is equipped with a highly stable pure complimentary service OCL circuit directly connected to all stages including one differential amplifier.
The output stage is of parallel push-pull configuration.

A 10,000 μ Fx2 electrolytic capacitor is used for the power supply.

Equipped with microphone mixing circuit with independent volume.

Equipped with a tape duplicate switch, you can copy between two decks at the same time.

The tone control section allows 2-step switching of both high and low turnover frequency.
It also has a defeat position.

Equipped with low filter and high filter.

The volume uses a 22-point click type high precision attenuator.

Equipped with 3-stage switching audio muting of 0, -10 and -20dB.

Actually measured data sheet is included.
This data sheet contains five items : input sensitivity (Phono, Aux), continuous output, harmonic distortion factor, SN ratio, and Phono maximum allowable input.

Model Rating

Type	Pre-main amplifier
Circuit system	Pure complimentary service OCL circuit directly connected to all stages
Power Amplifier Unit
Output (both channel drive)	Continuous output (1 kH) : 20 Hz to 20 kHz output : 45W + 45W (8 Ω) 55W + 55W (4 Ω) 42W + 42W (8 Ω) 50W + 50W (4 Ω)
Harmonic distortion factor	0.3% or Less (Continuous Output) 0.05% or Less (at 1W Output)
Cross modulation distortion factor	0.3% or Less (Continuous Output) 0.05% or Less (at 1W Output)
Output Bandwidth (IHF)	5 Hz ~ 40 kHz (8 Ω)
Damping factor	25 (8 Ω)
Residual noise	1 mv (8 Ω)
Preamplifier Section
Input Sensitivity / Impedance	Phono1, 2 : 2.5mV/50k Ω Aux, Tuner, Tape : 150mV/50k Ω
Recorded output	Tape rec:150mV DIN:30mV
Equalizer allowable input	MAG:350mV(RMS)
RIAA deviation	± 0.3 dB
Signal-to-noise ratio (IHF)	Phono:70dB Aux, Tuner : 90 dB
Frequency characteristic	10 Hz to 50 kHz + 0 -1dB
Tone control	Bass: Treble: ± 10 dB, ± 7 dB (100 Hz) Turnover : 400 hz, 200 hz ± 10 db, ± 7 db (10 khz) Turnover : 2.5 khz, 5 khz
Muting	-10dB, -20dB
Filter	Low:30Hz High:8kHz
Loudness	+ 8.5 dB (100 Hz), + 3.5 dB (10 kHz)
<General>
Semiconductor used	Transistor : 43 Diode : 16 pcs
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	125W
External dimensions	Width 450x Height 148x Depth 375 mm
Weight	11.5kg