Audio Database

L-507
Commentary

This pre-main amplifier was announced as the highest level of the 500 series which represents Lux.

The main amplifier uses a pure complimentary service system directly connected to all stages.
NPN type and PNP type power transistors are Darlington connected to the B-class operation part of the power stage respectively. In order to make the switching characteristics of the upper half cycle and the lower half cycle perfectly symmetrical, a pair of power transistors with the same current amplification factor (hfe) is adopted. In both the output stage and the B-class driver stage, transistors with excellent high-frequency characteristics and breakdown resistance are adopted to increase reliability when the output terminal is short-circuited.
The pre-driver stage employs a transistor with a high cut-off frequency and a particularly small collector output capacitance, making up a two stage differential amplifier circuit with low current drive. By driving with a constant current from no signal to maximum output, the B-class operation stage is kept in a stable state and notching distortion is suppressed.

The equalizer stage of the preamplifier section employs a 3-stage direct-coupled circuit composed of NPN type, PNP type and NPN type transistors, which are advantageous in voltage utilization factor, to obtain excellent linearity and improve DC stability by providing sufficient DC feedback.
The deviation from the standard RIAA curve is kept within ± 0.5 dB by reducing the tolerance of the parts used and suppressing dispersion.

The tone control circuit is an NF type of Lux-type with a simple variable characteristic. The frequency at which the curve point begins to change can be switched by 3 points at each of low and high frequencies, making it possible to adjust the sound quality more precisely.
Tone defeat is also possible.

The filter circuit is CR type for low-cut and NF type for high-cut.
The low boost circuit is an NF type.

The SN ratio has been improved by using ultra-low noise transistors in all stages of the pre-section.
In addition, the input and output circuit capacitors are selected from among Meiler capacitors and tantalum capacitors with less leakage current, thereby suppressing shock noise when switching switches.

Two 10,000 μ F electrolytic capacitors are used for the filter circuit of the power supply.
In addition, a muting circuit is installed to suppress shock noise when power is turned on or off.

Model Rating
Type Stereo integrated amplifier
Main Amplifier Section
Continuous effective output 50W + 50W (8 Ω, both channels operate simultaneously)
60W/60W (8 Ω, single-channel operation)
Total harmonic distortion factor 0.03% or Less (8 Ω, 50W)
Cross modulation distortion factor 0.04% or Less (8 Ω, 50W, 70 hz : 7 khz = 4 : 1)
Output bandwidth 5 Hz to 50 kHz -3dB (0.1%)
Input Sensitivity / Impedance 580mV/50k Ω
Residual noise 0.5 mV or less
Damping factor 40 (8 Ω, 20 Hz to 20 kHz)
Attachment Attenuator (-18dB)
Main speaker switch
Remote speaker switch
Headphone jack
Preamplifier Section
Standard output voltage Pre out:580mV
Rec out:100mV
Maximum output voltage Pre out:5V
Output impedance Pre out : Approx. 100 Ω
Rec out : Approximately 100 Ω
Frequency characteristic 10 Hz to 50 kHz -1dB (Aux1)
Total harmonic distortion factor 0.04% or Less (Aux1, 1 khz, 1 v)
Input sensitivity Phono1, 2 : 2.4 mV
Tuner : 100 mV (with input level set)
Aux1, 2 : 100 mv
Mic:2.4mV
Input impedance Phono1 : 50k Ω, 65k Ω, 90k Ω, switching
Phono2 : 65k Ω
Tuner : 50k Ω
Aux1, 2 : 50k Ω
Mic : 50k Ω
Signal-to-noise ratio Phono1, 2 : 65 dB or more
Mic : 60 dB or more
Tuner, Aux1, 2 : 80 dB or more
Maximum allowable input Phono : 300 mv (1 khz, R ・ M ・ S)
Tone control LUX System NF Type with Bending Point Switching
Low-pass curve point : 150 Hz, 300 Hz, 600 Hz
High-frequency bending point : 1.5 kHz, 3 kHz, 6 kHz
Filter Low-cut : 30 Hz, 6dB/oct.
High Cut : 8 kHz, 6dB/oct.
Low boost 70Hz
Attachment Tape Monitor Switch (2 systems)
Damping switch
Input impedance switching
Input level set
<General>
Semiconductor used
Transistor : 2SC1345 (12 pcs)
2SA640 (4 pcs)
2SA606 (2 pcs)
2SA620K (4 pcs)
2SC1103A (4 pcs)
2SC1431 (2 pcs)
2SA762 (2 pcs)
2SD388A (2 pcs)
2SB541A (2 pcs)
2SC853 (1 pc)
2SC735 (3 pcs)
2SA562 (1 Piece)
2SC496 (1 pc)
IC: TA7122AP (1 pc)
Diode : 1S1555V (2 pcs)
1N4003 (4 pcs)
1S188 (4 pcs)
Zener diode : WZ120 (2 pcs)
Barista : SV-03 (2 pcs)
SV-02 (2 pcs)
Power consumption 200W (8 Ω simultaneous load, maximum output)
External dimensions Width 450x Height 160x Depth 268 mm
Weight 11kg