Luxman C 1000 Service Manual

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SERVICE MANUAL

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MODEL: C-lOOO CONTROL CENTER

C I R C U I T D E S C R I P T I O N

Egualizer Stage

A Cascoded Differential Direct Coupled Amplifier is adopted. This differential circuitry
at the top stage stabilized the direct coupled stage and helps obtain better linearity. Also
this shields the NF amp immune from being unstabilized by the exterior effect such as cartridges
to be connected to the input. Good linearity, stability and SN ratio are ensured thanks to the
Cascoded Amplifier adopted for this differential stage and the following stage.

As for the output stage, the adoption of the transistor of TO-5 type at the final stage
together with the push-pull circuit by Class A Inverted Darlington Configuration permits to
accept the low impedance loads.

This is designed for the professional use because current standard control amp cannot stand
the severe load condition at equalizer stage when a lot of lines of recording output is used
frequently with professional equipment.

Constant Current CiICUits are adopted at important points to improve the linearity of the
transistor itself, the open loop gain and the differential function, all of which contribute to
lower the distortion. The permissible input voltage at PHONO terminals is 450mV at lKHz (R.M.S.
Input Sensitivity OdE).

R.I.A.A. equalization is within t0.2dB, which is realized by careful selection of components
used in this equalizer stage. Other function related to this stage are Input Sensitivity

Adjuster, Input Impedance Adjuster and Linear Equalizer.
Intermediate Amp & Tone Control Circuit

These two stages adopt cascoded direct-coupled amp to-improve linearity especailly at high
frequency range, and stability and SN ratio are just the same with that of the equalizer stage.

Constant Current Circuitry is adopted in the output stage to improve linearity of the
transistor ltself and the open loop gain. Phase compensation for NF stabilization is just one,
and the aggravation of the distortion at high frequency range is almost nil.

Tone Control Circuit of LUX original NF type improves the distortion together with the
above mentioned amplifying circuit. Tone control function is provided with independent frequency
selector with 3 points for both bass (lSOHz, 3OOHz, 600Hz) and treble (1.5KHz, SKHz, GKHz)
together with the tone defeat switch. This circuit allows low boost at the same time. Thus
wider tonal adjustment is feasible.

Further a detent-volume of 21 points bype is adopted for both bass and treble level control.
This is just the same type with the high-grade attenuator, which prevents gang error between
right and left channel.

Buffer Circuit

Emitter follower circuit is adopted for this stage. But this is somewhat different from
the ordinary one. Here two transistors are used; one is for the emitter follower and the other
for the constant current circuit to the emitter follower stage. This constant current driving
circuit not only keeps good linearity of the transistor itself but suppresses the distortion

lowest for wide frequency range by means of its high open gain.
Filter Circuit

This stage is an NF type utilizing emitter follower. The constant drive system is adopted
likewise the Buffer stage. Cut off frequency can be selected either at lOHz (-18dB/oct.) or
70Hz (-lZdB/oct.) for Bass cut and 7KHz (-12dB/oct.) or lZKHz (-lZdB/oct.) for Treble cut.
Independent filter circuits for each cut off frequency are provided, and these cut off points
can be selected by the whole switching of the circuit. of course no signals will go through

these circuits when the filter switch is off.