Luxman 5 c 50 service manual

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w scso
SERVICE MANUAL

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CI RCUIT DkSCRIPTIO

EQLJALIZER CIRCUIT

A DC configuration anglifier is adopted, utilizing FET's at the top stage. The
differential circuit accompanied by cascode~bootstrap elnfiguration is driven into current-
mirwr load. The main circuitry is packed into a hybrid type LC. of wxs original Dual
Monolithic Linear I .C. (DML-az No. H40 in order to reduce DC-drift.

Signals from H101 are amplified by the cascade amp composed by QIOI and 0102, thus
reducing and stabilizing the feedback amount of transistors. which contributes to improve
characteristic or Linearity in high frequency range.

This equalizer circuit is of the NF type offering 36:13 gain at lime, and the over-
load voltage is SODmV (lkflz, EMS).

FLAT~AMP , LINEAR EQUALIZER

Almost same configuration as that of the equalizer circuit is adopted except the
feedback elements.

For the feedback elemnts. adapted are the frequency selective components, which
function as the Linear Equalizer by switching with the rotary switch 5301.

The Linear Equalizer provides the maximum variation of :1.SdB at approximately lkHz

axis and is operative on all signal sources. In the center "flat" position, these frequency
selective components are throughly bypassed to be a were flat amplifienmose gain is 16.5dn.

DC DRIP! SENSER

In case some leakage is found at the output terminals of these equipments connected
to the AUX or the TUNER terminal of the SCSI), the DC ingredients are applied as signals to the
input of this preamplifier. In the extreme case, the operational point of the flat amplifier is
shifted, therefore the DC drift sensor is provided to warn the presence of Dc ingredients at the
input by sensing the leakage a: the output of flat amplifier.

_ (s) voltage is detected by Q50! and Q503, while (-) voltage is detected by (1504,
both of which are amplified by Q506 and QSOS. When DC is shifted, the offset indicator lights
up to Him the DC drift. Actunlly, the offset indicator lights up when nc exceeding 350-! is
sensed at the output of flat amplifier, and the pilot lamp on the from; panel turns into red.

FILTERS

The filters of the SCSO are composed of the subsonic filter to cut the ultra low
freqmcy range and the active type high tut filter of duh/act. me subsonic filter consists
of the pnralled T-type filter (so-called tlin T-type) and the CR attenuation filter of -6da/oct.
The frequency can be selected by the lever switch 5004, and the cut off characteristic can be
varied by W006. The high cut filter is an active filter of emitter-follower type and provide a
cut off characteristic of ~12dE/oct. The frequency can be selected by $005.

The emitter~follower amplifier of constant current drive type composed of Q40! and
Q402 operates only as a buffer amplifier for the subsonic filter function, and operates as
elements for active filter when the high cut filter is turned on. The amplifier composed of
Q40! and (2402 is thoroughly bypassed when both of subsonic filter and high cut filter are turned
off.