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| LUXMAN L-58A |
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| 149,000yen(September, 1979 release) |
The Integrated Amplifier which aimed at improvement
of physical condition of the amplifier for the tone-quality modification instead
of a mere property modification by the original Duo beta circuit.
A Duo beta circuit means it as the circuitry which combined two NFB.
In this circuitry, many properties are improved by completing the good
amplifier of genius (nakedness property) rather than not applying a lot
of NFB and improving many properties of amplifier, and combining a little
NFB and DC servoes with this.
In the power amplifier part, the pure complimentary
differential push-pull circuit by FET 2SK163 for N channels and for P channels
(2SJ44) is adopted as an input stage, and the naked distorted property is
improved as a DC amplifier stream composition.
Moreover, from an input stage
to an output stage, all were constituted from a push-pull circuit, and
simultaneously, ft (high region cut-off frequency) was high, adopted the small
transistor and FET of Cob (collector output capacitance), and has reduced
distortion.
And while adopting as an output stage MOS FET (2SK134 and 2SJ49) whose
ft is about 500MHz and sending 300mA or more of bias currents, the "notchless
class A" to which the amplifier which does not carry out a switching
operation was made is made combining the high-speed driver circuitry.
Moreover, by
circuitry devices, such as adoption of an element, adoption of local NFB, etc.
which were excellent in the high region property, open loop gain (naked gain)
was lowered and the single figure naked frequency characteristic is improved.
In these results, the distortion of the nakedness of a power amplifier
part improves to 0.4% (it is 2 to 5% conventionally), and the slew rate
has improved at 300v/μsec sec (it is 10v/microsec conventionally).
In the equalizer part, the cascode input type bootstrap circuit by FET4 stone adoption s Is in the input stage, a dynamic-resistance circuitry with a transistor is combined, and distortion of nakedness is suppressed.
Moreover, in order to stop an Output
load impedance low as much as possible, the SEPP circuit (single ended push-pull
circuit) by transistor 4 stone is adopted, and distortion of nakedness is
reduced.
In these results, the distortion of the nakedness of a preamplifier part
(equalizer stage) improves to 0.2% (2 to 5% of the former), and the slew
rate has improved at 150v/μsec sec (it is 10v/microsec conventionally).
In the Duo beta circuit, 1/100 or less conventional NFB is applied to this
amplifier circuitry. This reduced TIM distortion and the tone quality of
a mid-high range is improved.
In order that the firm low-pass play, the fall of the dumping factor generated
by having reduced the amount of NFB, the cone excursion of a speaker, etc.
may prevent cross modulation distortion and an SN ratio from getting worse,
original DC servo circuitry is adopted in the Duo beta circuit.
A little these DC servo
circuitries are parallel combined with the NFB circuitry, since they have adopted low-noise FET amplifier, can use a good film capacitor for a filter
circuit, and are enabling the firm low-pass play.
Since priority is
given to a tone quality, many FETs of the input were not connected but it has
been dared to adopt DC amplifier stream composition by the parallel connection
of FET with the head amplifier for MC.
While connecting parallel FET for N
channels which was excellent in the Noise Figure, it has DC amplifier
composition which has improved the high region property especially combining a
constant current circuit. Although this is disadvantageous somewhat by the SN
ratio substantially, if the impedance of MC cartridge which connects changes,
the gain automatic-regulation scheme which adjusts amplification degree automatically would be adopted, and this problem will be solved.
It has
composition which banishes the flat amplifier leading to a tone-quality failure, and covers the amplification degree running short in a power amplifier
circuitry. For this reason, in order for a tone control circuit to prevent
receiving influence in other circuitries, buffer amplifier is formed in the
preceding paragraph of the tone control.
The source follower circuitry of the cascode interconnection by an FET
input is used for a buffer circuit and a tone control circuit. Moreover,
the circuitry which can change a curving point with NF type of a LUX scheme
is adopted as a tone control circuit.
Moreover, since it is at the time which does not need a tone
control, it enables it to bypass these circuitries.
In the power circuit
of a power part, while adopting a measure against tone quality type mass block
capacitor, the film capacitor was combined parallel and the high region property
is improved.
Moreover, the transistor for power with a quick switching speed
was used for the constant-voltage regulated power supply for preamplifier parts, and it has fully lowered the circuit impedance.
Furthermore, a
constant-voltage regulated power supply is adopted as the pre-driver stages of a
power amplifier part, and the stabilization of operation is attained.
In
order to suppress to the minimum that the metals chassis inside amplifier
interferes in a product-line circuitry, it is made the structure which hollowed
the chassis corresponding to the printed circuit board.
Moreover, eddy
current distortion is eliminated thoroughly, such as adopting the wooden box of
real wood as a cabinet, also extracting the shielding to necessary minimum, and
using ultra-thin aluminum foil.
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| Form |
Stereo integrated amplifier
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| Succession effective output |
80W+80W (8 ohms, both ch operation, 1kHz) |
| THD |
0.009% or less (8 ohms, Output-power-3dB,
20Hz - 20kHz) |
| Cross modulation distortion |
0.009% or less (8 ohms, Output-power-3dB,
60Hz:7kHz=4:1) |
| Frequency characteristic |
Phono man month: 20Hz-20kHz±0.3dB
Tuner,
AUX, Monitor1, 2:10Hz - -100kHz three dB |
| Input sensitivity/impedance |
Phono man month: 1.6mV/50kohm
Phono
MC-1:1.6mV/100 ohms
Phono MC-2:0.25mV/100 ohms
Tuner, AUX, Monitor1,
2:200mV/40kohm |
| SN ratio (IHF-A) |
Phono man month: 80dB or more
Tuner,
AUX, Monitor1, 2:110dB or more |
| Tone control |
The point curving [ low-pass ]: 200Hz, 400Hz
(defeat is possible)
The point curving [ high region ]: 2kHz, 4kHz (defeat
is possible) |
| Filter |
Subsonic speed: 15Hz, off, 30Hz
A high
cut: 9kHz, off, 15kHz |
| A low boost |
70Hz, off, 150Hz |
| Attachment |
Phone straight switchpoint
Mono-switchpoint
Signal-off switchpoint
Warmup indicator
Speaker
selector
Headset jack |
| Supply voltage |
AC100V, 50Hz/60Hz |
| AC outlet |
Power-switch interlock: 100W
Power-switch un-interlocking.: 100W |
| Power consumption |
180W (Electrical Appliance and Material
Control Law) |
| Dimensions |
Width 464x height 156x depth of 332mm
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| Weight |
11.0kg |
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