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| Accuphase C-280V |
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| 800,000 yen(December, 1990 release) |
The stereo preamplifier developed aiming at the extreme on the basis of the
development technology acquired by C-280 and C-280L.
The balance
transmission system is adopted as a line amplifier part.
This circuit
consists of three differential amplifier fundamentally, and has the structure
where amp1 takes charge of an input and amp2/amp3 take charge of an output. At
the time of balance, from +-both the inputs of amp1, a signal enters, and is
amplified, and it is inputted into the following amp2/amp3, respectively. 2 sets
of these amplifier has a relation of tucking up its sleeves with a cord which
feeds back each output to the other party, and sends out the symmetrical signal
of +- by low impedance.
The feature of this circuit is that both of
amplifier operates even if it grounds one side of an output, and it can take out
a double output. For this reason, it operates normally only by input and output
connecting either to a grand (ground) line at the time of the imbalanced
connection by the usual phono jack.
By this composition, the composition of
amplifier changes neither as imbalanced as balance, but outstanding
magnification is enabled.
Each unit amplifier of line amplifier consists
of symmetrical type push pull circuits of Accuphase original.
Operation
whose input circuit is a cascode sauce follower and which was stabilized to the
super-high region is realized, and the output stage has realized the low Output
load impedance and the outstanding linearity by the complimentary Darlington
push pull.
All of these unit amplifier consist of direct connection
amplifier, and it has prevented generating of direct-current drift by
direct-current servo circuit in order to stop the shocking noise by a part
generated in an output flowed in one direction.
The full independence
power source of four transformers which separated not only right-and-left
separation but the equalizer is adopted as a power-source part. For this reason,
the full capacity of the filter capacitor amounts to 120,000 micro F.
Furthermore, the broadband constant-voltage power source was carried in all
the unit amplifier, and the mutual intervention between amplifier is prevented
thoroughly.
The adjustor developed specially because of C-280V is
adopted as a volume control part.
CP (conductive plastic) element used as an
object for studio is used for the resistance object, and CP resistance object is
finishing the surface in the shape of a specular surface by carrying out high
temperature pressurization plastic surgery after printing a resistive element, and has realized low contact resistance and a low distortion.
The brush in
contact with a resistance object has adopted the gilding many contact type, is
made into an external terminal and solid construction, abolishes a metal
composition plane, and is reducing different-species metal distortion. Moreover,
the rotary system has the structure where this is fixed and a resistance object
rotates instead of the method which a brush rotates. Thereby, an internal
contact surface decreases sharply, and contact grease also becomes unnecessary
and it is improving durability.
Furthermore, a brass shaft 8mm in diameter
is supported by an aluminum cutting bearing, four elements are stored in a high
precision aluminum cutting case, respectively, a perfect shield is given, and
improvement in sound quality is aimed at.
A variable system is continuation
good transformation and the tracking error has realized outstanding accuracy of survey of less than 0.5dB in a position of -60dB.
The logic relay
control circuit is adopted as the change of a signal. The relay was installed in
the required place, and with the circuit system which controls these
electronically in a logic circuit, the change suppressed leading about of an
unnecessary signal course, and has prevented signal degradation.
In this
case, the full sealing structure relay containing [ which was developed the
object for audios and for communication machines ] nitrogen gas is adopted
especially as the relay used, and it requires. The contact which influences
sound quality is a crossbar twin system of gold and a silver palladium alloy, and has become low contact resistance and a thing of high durability which has
high quality.
All the circuit symmetrical type push pull circuits are adopted as equalizer amplifier.
It has the exclusive input circuit which
matched the cartridge of each MM/MC, and constitutes from an FET element of high
S/N at the time of MM input.
Moreover, since a minute signal is received by
low impedance, the difference input circuit by a low noise element is
constituted at the time of MC input, and it enables little reproduction of noise
by attaining low impedance-ization of a NFB loop.
Furthermore, in order to
take the characteristic of a cartridge, and matching, MC input impedance serves
as a three-kind change type, and a profit can also be chosen from two kinds.
It is quantity 造 which was attached to the unit amplifier of a total of six right and left of line-in, line-out, and a phone equalizer, and stored the
constant-voltage power-source part for exclusive use in thick aluminum housing
at it, respectively.
It is being firmly fixed to housing to serve also as
heat dissipation, and the element of an output and a constant-voltage power
source has prevented resonance by vibration.
The whole structure is the
framework structure by the hard aluminum of 8mm thickness, the mother board of
thick glass epoxy is firmly attached to this, and aluminum housing is being
fixed with the screw.
The characteristic jack of rhodium plating is used
for an input-and-output jack. Rhodium plating has a track record as a connector
of a communication machine or a computer, and has the outstanding durability.
Five step type rotary type Attenuator is carried so that a volume
controller may be left as it is and volume can be adjusted in an instant.
It is possible to make channel balance perfect, to carry the
right-and-left independent Attenuator type level control which can control the
normal position by arbitrary listening positions, and to adjust for 0 - -6dB
correctly at intervals of 1dB to -14dB a 0.5dB step and henceforth.
The
resistive element has adopted the low distortion type of specular surface
finishing.
The phase of the whole equipment was reversed and the phase
switch which adjusts an absolute phase is formed.
In order that a change
system may only replace + and - of balance amplifier and may not have a load
circuit like a phase inversion machine, there is no sound quality degradation.
The Compensation switch which improves the shortage of massive at the
time of small volume is carried.
With the position of the volume controller,
the characteristic is rectified automatically and natural balance is maintained.
The Subsonic Filter is carried.
The front panel has adopted what
gave the gold tone scratch hair line to the thick aluminum of Accuphase
tradition, and has stored the main part in the persimmon wood case.
|
| Form |
Stereo preamplifier |
| Frequency response |
| balanced input (CD, Line) : |
1.0Hz-350kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2
dB |
| CD, Tuner, Line, Tape Play : |
1.0Hz-350kHz+0 -3.0 dB
20Hz-20kHz+0 -0.2
dB |
AD: 20Hz-20kHz±0.2dB
|
| THD |
0.005% (with all the input terminals)
|
Input sensitivity/impedance
(at the time
of an Output power / 0.5V output) |
AD MM: 2.0mV/0.5mV/47kohm
AD MC
(26dB): 0.1mV/0.025 mV/10ohm, 30ohm, 100ohm
AD MC (32dB): 0.05mV/0.0125
mV/10ohm, 30ohm, 100ohm
Balanced: 252mV/63mV/40kohm (20kohm/20kohm)
Unbalanced: 252mV/63mV/20kohm |
| An Output power/impedance |
Balanced output: 2.0V/10 ohm (5ohm/5ohm)
Unbalanced output: 2.0V/5 ohm
Tape rec: 252mV/200 ohms |
| S/N and input conversion noise |
| Input terminal
|
Input
short-circuit IHF-A compensation |
EIA S/N
|
| Rated input S/N |
Input conversion noise
|
| AD MM: |
90dB |
-140dBV |
86dB |
| AD MC(26dB): |
80dB |
-154dBV |
85dB |
| AD MC(32dB): |
75dB |
-154dBV |
85dB |
| Balanced: |
111dB |
-123dBV |
95dB |
| Unbalanced: |
111dB |
-123dBV |
95dB
|
|
Maximum-except-take-off level
(0.005% of
a distortion, 20Hz - 20kHz) |
Balanced output:7.0V
Unbalanced
output:7.0V
Tape rec:19.0V |
The AD maximum inlet pressure
(1kHz,
0.005% of distortion) |
MM:300mV
MC(26dB):15mV
MC(32dB):7.5mV |
| Minimum load impedance |
Balanced output: 600ohms (300ohm/300ohm)
Unbalanced output: 600ohms
Tape rec: 10kohm |
| Gain |
Balanced input->Balanced output: 18dB
Balanced input->Unbalanced output: 18dB
Unbalanced input->Balanced
output: 18dB
Unbalanced input->Unbalanced output: 18dB
Unbalanced
input->rec output: 0dB
AD MM input->Balanced output: 54dB
AD MM
input->Unbalanced output: 54dB
AD MM input->rec output: 36dB
AD
MC(26/32dB) input->Balanced output: 80 / 86dB
AD MC(26/32dB)
input->Unbalanced output: 80 / 86dB
AD MC(26/32dB) input->rec output:
62 / 68dB |
Loudness Compensation
(Volume -30dB)
|
1:+3dB(100Hz)
2: +8dB (100Hz), +6dB
(20kHz) |
| Subsonic Filter |
10Hz, -18 dB/oct |
| Attenuator |
- 6dB-20dB-30dB, -infinity |
| The semiconductor used |
Transistor: 216 pieces
FET: 15 pieces
IC: 18 pieces
Diode: 158 pieces |
| Power supply voltage |
AC100V/117V/220V/240V, 50Hz/60Hz
|
| Power consumption |
53W |
| Dimensions |
Width 468x height 171x depth of 415mm
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| Weight |
25.2kg |
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