Audio Database

The

LUXMAN L-550
250,000yen(November, 1981 release)

Description
 
The Integrated Amplifier which carries a DUObeta circuit / S.

In addition to the power source plusX of the DUObeta circuit which combined "proper-quantity NFB" and "DC servo", and a control feedback of tone-quality dominance, the DUObeta circuit / S which furthermore, added "one-step amplification amplifier" are developed, and it carries in the equalizer and the power part.
One-step amplification amplifier has adopted FET for MC head amplifier as the first rank, and has the structure of taking out gain required for high gm and this FET of a low-noise by sending the large current of 7mA per one stone from the first.
After making an output stage become independent completely so that it can come, simultaneously there may be no influence in the first rank, the 2nd step is removed, and the voltage amplification has realized the ideal circuitry only of one step.

The output unit is the intrinsic Class-A operation which fixes a bias current, and has realized Oide power of 50 W/ch.
In a lot of exothermics by Class-A operation, it corresponds by two large-sized heat pipes, and this heat pipe is considering it as a symmetric figure, and has banished heat-dissipation sound.

One-step amplification amplifier is adopted also as a head amplifier part.
The low-noise is realized making the very low PNP transistor of input equivalent resistance into a single differential at the first rank, and obtaining sufficient gain.

An input selector, light filters, a monophonic switchpoint, a balance control, etc. are separated at the time of a disk play, and the phone straight functionality which links an equalizer and power amplifier directly is carried.

Since sound-recording frequencies, such as a disk, may be rising gently toward a high region or may be descending conversely, such a peculiarity is rectified and the linear equalizer which returns recording characteristics to a flat is carried.

A high region and low-pass one carry the tone control which can choose nine turnover frequencies.
It is the design which thought as important the frequency which begins a transition rather than the variation, and the Lux scheme NF type tone control from which a gentle transition property is acquired is adopted.

The capacity of 400VA was given to the power-source part using the requests-for-price-quotations EI core, and the power transformer which hardened the interior by silica sand and suppressed the temperature rise is adopted as it.
Moreover, the thing with a capacity of 30,000 micro F is employed full time as an electrolytic capacitor two times by 99.99% of an aluminum purity, and ending with a tone-quality measure.

The Puri heating functionality is carried, and a small-quantity electric current can be sent and warmed.

The warmup indicator is carried and it can check having gone into operational stability.

The line phase sensor is carried, the polarity of the AC power source of an it1 is detected, and a tone-quality mandatory is possible.

Internal

Rating of a mode
Form Integrated amplifier
Effective output 50W+50W (a Class-A operation, 8 ohms, both channel operation)
THD 0.005% or less (8 ohms, both channel operation, -3dB)
Input sensitivity Phono MM:1.6mV
Phono MC: 80 microvolts
Tuner, AUX, Monitor, Main In: 220mV
Input impedance Phono man month: 100kohm, 50kohm, 100ohms
Phono MC: 300 ohms, 100ohm, 40ohm
Tuner, AUX, Monitor:40kohm
Main In: 47kohm
SN ratio (IHF-A) Phono MM:84dB
Phono MC: 80dB (250-microvolt input)
Tuner, AUX, Monitor, Main In: 110dB
Frequency characteristic 10Hz - -100kHz one dB
Tone control Low-pass turnover: 55Hz, 77Hz, 110Hz, 155Hz, 220Hz, 310Hz, 440Hz, 620Hz, 820Hz
High region turnover: 620Hz, 880Hz, 1.2kHz, 1.7kHz, 2.5kHz, 3.5kHz, 5kHz, 7kHz, 10kHz
The maximum variation: ±9dB
Tapes monitor Three lines (Tape1, 2, Tape Front)
Tapes dubbing Four lines (1->2, 2->1, 1 ->Front, Front->1)
Linear equalizer up tilt, down tilt: Two steps each (one step 1dB)
Power consumption 310W
Dimensions Width 453x height 174x depth of 460mm
Weight 21.4kg