Luxman LX38 Stereo putkivahvistin

Erittäin hyvässä kunnossa laatuvahvistin. Japanilainen versio 100V.

Laadukas muuntaja mukaan. Huolto tehty huhtikuussa 2023.

Commentary

This tube type stereo integrated amplifier is the fourth generation of 38 series from the first stage SQ38F released in August 1973.

The preamp section consists of a flat amplifier circuit that also functions as an equalizer circuit and tone control circuit. Each circuit is fully developed to improve the characteristics.

The equalizer circuit employs a two stage P-K NF method (a method in which a blowing sensation is applied from the second stage plate to the first stage cathode) that provides low distortion characteristics and excellent stability over the entire band. In addition, the equalizer circuit is set at an operating point where the current of the output stage is increased to improve the input resistance in the mid - and high-frequency range.

The tone control circuit, which also serves as a flat amplifier, adopts the 2-stage P-K NF method to improve the distortion factor characteristics.

Low-noise type 12AX7 and 12AU7 are used in the pre-section. Especially, ultra-low-noise type is used carefully for the first stage of the equalizer circuit.

For the output tube of the power amplifier section, a 3-pole tube 50CA10 with low internal resistance and excellent bare characteristics is used for AB class operation. In order to bring out the performance of this sphere, a newly designed output transformer is used.

This transformer reduces the power loss to less than 1/2 compared with the conventional OY15 type by increasing the diameter of the wire used, and realizes improved frequency characteristics, phase characteristics and AC balance by unifying the secondary winding using the wide optimum load range of the 3-pole output tube.

The driver circuit is based on a Mulard type drive circuit (cathode-coupled phase-inversion circuit) that has few time-constant circuits in the low-frequency range and is more stable and can gain more gain. The first stage 6267 uses three connections, and the latter stage of phase-inversion uses a triode 6AQ8 and triode in all stages to improve the distortion factor characteristics in the high-frequency range. In addition, the operating point of this driver circuit is made variable, and it is adjusted one by one to cancel out the distortion in the output stage.

The tone control function consists of a 3-point bending point switch for both low and high frequencies. The level adjustment is linked to the left and right channels. The adjustment volume uses a new multi-slider type volume and is equipped with a defeat switch.

The CR type filter is used for both high and low frequencies, and can be switched at 2 points each.

Other built-in functions include a low boost function, a tape monitor circuit, a tape dubbing function, a Rec out off function to disconnect the recording output terminal, and a -20dB attenuator.

The mechanism has been completely reconsidered, and by simplifying the signal path and adopting a printed circuit board, the characteristics and stability are improved.

In addition, the speaker switching and impedance switching of the output circuit are eliminated to prevent deterioration of sound quality caused by excessive switch contact passage.

The volume and balancer employ a highly accurate multi-slider type volume that can almost ignore the linkage error between the left and right channels.

We have also adopted film type coupling capacitors and highly reliable switches.

There was a wood cabinet sold separately.

Model Rating

Type Bulb-tube stereo integrated amplifier

Continuous execution output 30W/30W (8 , 4 )

25W/25W (16 )

25W + 25W (8 , both channel operation, 50 Hz to 15 kHz)

Total harmonic distortion factor (8 ) 0.1% or Less (10W, 1 kHz)

0.4% or Less (1 kHz at Rated Output)

1% or Less (50 Hz to 15 kHz at Rated Output)

Cross modulation distortion factor 0.4% or Less (8 , Rated Output, 60 Hz : 7 khz = 4 : 1)

Frequency characteristic 30 Hz to 40 kHz -1dB (8 , 1W)

Input sensitivity Phono1, 2 : 2 mV

Tuner, Aux1, 2, Monitor1, 2 : 160 mv

Input impedance Phono1, 2 : 50k

Tuner, Aux1, 2, Monitor1, 2 : 100k

SN ratio (IHF-A correction, input short) Phono1, 2 : 75 dB or more

Tuner, Aux1, 2, Monitor1, 2 : 95 dB or more

Damping factor 16 or More (8 , 1 kHz)

Tone control LUX System NF Type with Bending Point Frequency Switching (Capable of Defeat)

Low-pass curve point : 150 Hz, 300 Hz, 600 Hz

High-frequency bending point : 1.5 kHz, 3 kHz, 6 kHz

Attachment Low-boost switch (50 hz, off, 100 hz)

Low-cut filter (60 hz, off, 20 hz)

High Cut Filter (7 khz, off, 12 khz)

Monitor switches (tape-1, source, tape-2)

Tape dubbing switch (1to2, source, 2to1)

Recording switch

Attenuator (-20dB)

Vacuum tube used 50CA10 : 4 pieces

6AQ8 : 2 pieces

6267 : 2 pieces

12AX7 : 3 Pieces

12AU7 : 1 piece

Power supply voltage 100 VAC, 50Hz/60Hz

Power consumption 150W (Electrical Appliance and Material Control Law)

External dimensions Width 440x Height 162x Depth 343 mm

Weight 20.1kg