LUXMAN C-7

Commentary

A control amplifier that employs a fully balanced CSSC circuit.

The C-7 adopts a fully balanced configuration of CSSC (Complimentary Single Stagger Circuit) circuit of pure complimentary service configuration directly connected to all stages.
In the second stage of the CSSC circuit, a grounded base type current transmission circuit is adopted. The cut-off frequency is set high enough to realize natural signal amplification without extra phase correction. In the C-7, this CSSC circuit is made into a fully balanced configuration, and the ground potential difference is completely eliminated to clarify the reference point. This allows each amplifier to operate on the same time axis to completely eliminate the phase difference and cancel out the noise mixed in the signal to further improve sound quality.
For impedance conversion to ensure input signal stability, a discrete buffer amplifier of complimentary service configuration with extremely high-speed characteristics is adopted to keep input impedance sufficiently high.

It adopts OD β (Optimaized Dual NFB) circuit which integrates NFB technology accumulated by LAX for many years.
In general amplifiers, NFB is used to adjust the sound quality in the playback band. AC NFB affects the sound quality in the middle and high range, and DC NFB affects the sound quality in the low range. In this DC and AC separate feedback method, a DC servo amplifier is inserted to control DC feedback, which has a large influence on the low range. Therefore, the sound quality in the middle and low range is inconsistent.
The OD β circuit used in the C-7 incorporates the bare characteristics of the circuit. By applying 100% DC feedback, DC stability is ensured while eliminating the DC servo amplifier. All bands are unified with natural tones.

A unique high-inertia power supply is used for the power supply.
In the high-inertia power supply system, the instantaneous power supply capability is improved by the adoption of custom electrolytic capacitors, while the regulation is enhanced. The total stability of the regulator circuit itself is ensured by improving the bare characteristics. In addition, excessive control that is delayed from the real time of music is minimized. By performing only the minimum necessary control, unnatural voltage fluctuations that fluctuate little by little are changed into loose fluctuations, making it possible to supply power that produces sound quality that is natural to the listener.

It is based on a large mass FRP chassis base of 5-point grounding type with excellent vibration absorption mode, and realizes high rigidity construction which suppresses unnecessary vibration by firmly fixing parts to a thick hard chassis.
In addition, noise countermeasures are taken thoroughly. In order to prevent the generation of flux and noise caused by the general arrangement of adjacent power transformers, chemical capacitors, and amplifiers, they are laid out in a positional relation so that they do not directly interfere with each other, and each block is cut off by a shield plate.
Furthermore, each stage is reasonably segmented to eliminate high-frequency noise and leakage flux.

An independent power supply room system has been adopted as a countermeasure against leakage flux in the power supply section.
The external power supply system used as a a countermeasure against leakage flux, the instantaneous supply capability is lost due to an increase in supply impedance, and the efficiency as a regulator power supply is reduced.
The C-7 uses an independent power supply room structure that completely separates power supplies such as transformers, rectifier diodes, and block capacitors from the signal path. This structure allows the power supply to be contained within the same housing and eliminates leakage flux. In addition, the C-7 is connected to the chassis of the main body in a semi-floating manner so that it is insulated from various vibration and noise.
In addition, the constant voltage circuit is placed on the amplifier side to suppress the effect of control time delay and interference noise.

Custom parts are used everywhere to achieve a high level of sound quality.
The C-7 uses large non-magnetic high-sound-quality carbon film resistors, electrolytic capacitors, copper-styrene capacitors, and other custom-made products that meet the rack specifications. In addition, a closed-type gold-plated contact relay is used for various switching functions, and the contact area is increased by polishing the contact to improve the information transmission capability.

For the level control, 4-row type level control with low distortion rate and low noise for perfect balance is adopted.
This volume has been newly developed considering various aspects such as noise and phase problems caused by contact points.

The tone control uses a NF type Lux-type tone controller.

The input jacks are equipped with a coaxial Line 5 and two balanced systems, and the output jacks are equipped with two coaxial and two balanced systems. Bi-amp drives can be connected in both balanced and unbalanced modes.
Two tape input / output systems are installed.

Equipped with a line phase sensor, the polarity of the power supply can be checked at a glance.

The power cable uses custom-made products with particular attention to sound quality.
This cable is an AC inlet type.

It is equipped with a remote terminal. By connecting to the B-10 or M-7 power amplifier of Lux, the power on / off of the power amplifier can be linked with the C-7.

A 15 mm thick aluminum panel is used for the front panel, and a glossy wooden cabinet is used for the cabinet.

There was a version upgrade service from C-7 to C-7i.

Model Rating

Type	Control amplifier
Input Sensitivity / Impedance	Tuner, CD, Line1-3 : 150mV/50k Ω Balance Line1/2 : 150mV/100k Ω
Output Level / Impedance	Co-axial : rated 1V/300 ohm 7.5 v max. Balance : Rated 1V/600 Ω 7.5 v max.
Total harmonic distortion factor	0.005% or less (rated)
Frequency characteristic	20 Hz ~ 20 kHz + 0 -0.1 dB
Signal-to-noise ratio	110 dB or more
Tone control	Treble : Turnover 3 kHz, max ± 8 dB, 10 kHz ± 6 dB Bass : turnover 300 Hz, max + / - 8 dB, 100 Hz + / - 6 dB
Attachment	Tape Dubbing 2 Systems (1 → 2, 2 → 1) Rec off Straight-through switch Output mode selector switch Remote (Power) output Line phase sensor Output phase selector switch
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	38W (Electrical Appliance and Material Control Law)
Maximum external dimensions	Width 467x Height 187x Depth 435 mm
Weight	18.0kg
Other	Upgrade to C7i (¥ 50,000)