m Current feedback circuit topology assures great sound and stable
operation m Printed circuit boards using Teflon base m Fully modular
construction with separate units for all amplifier stages m Balanced
output stage with bridged feedback m Complete mono construction
with separate left/right transformers m Logic-controlled relays for
shortest signal paths m Optional analog record playback capability

The new joy of analog – realized in a superb high-end preamplifier.
Current feedback technology, Teflon-based printed circuit boards, fourseparate unit amplifiers, fully dual-mono construction with separate
power supplies. Optional phono equalizer unit allows top-quality analog
disc reproduction.

Current feedback topology prevents phaseshifts
The amplifying circuits in the C-275V use the current
feedback principle for negative feedback. Figure 2
shows the operating principle of this design. At theinput point of the feedback loop, the impedance iskept low for current detection. A trans-impedance
amplifier converts the current into a voltage to be
used as the feedback signal. Since the impedanceat the current feedback point (current adder in Figure2) is very low, there is almost no phase shift. Phase
compensation therefore can be kept at a minimum.
A minimal amount of NFB results in maximum
improvement of circuit parameters. The result isexcellent transient response and superb sonictransparency, coupled with utterly natural energybalance.
Figure 3 showsf r e q u e n c y (High)
response fordifferent gain
settings of thecurrent feedback
amplifier. The(High)Frequencygraphs demonstrate that response remains
uniform over a wide range.
GainAll preamplifiers from Accuphase are based onbalanced signal transmission, taking a nocompromise approach to quality. Furthermore, theyreflect the rich experience accumulated by
Accuphase during many years of building state-ofthe-art components. The C-275V is a fully
redesigned successor to the C-275, making
extensive use of sophisticated technology first
introduced in the highly renowned C-290V. As ananalog preamplifier, it has been honed to an evenhigher degree of perfection. Every single part was
carefully selected through intensive listening tests.
It offers a full complement of sound tailoring featuressuch as tone controls and a loudness compensator.
The basic circuit design employs current feedback
topology developed by Accuphase, assuring
outstanding performance combined with excellent
sound quality.
As shown in Figure 1, in its standard configuration
the C-275V is a dedicated line amplifier, but by
installing an optional phono equalizer unit in a
special slot on the rear panel, it allows high-grade
analog disc reproduction as well.
In keeping with the aim of creating the ideal line
amplifier, the balanced output stage of the C-275V
employs symmetrically bridged feedback, resulting
in a floating design where the signal is kept entirely
separate from the ground line. This lavish approachis highly desirable in a line amplifier and assures
the best possible performance. The printed circuitboards are an important element of a preamplifier
in regards to electrical performance as well as soundquality. In the C-275V, these are made from a Teflonmaterial (glass fluorocarbon resin) with low dielectric
constant and low loss, for optimum sound.
Less frequently used controls are located behind a
sub panel, and the elegant gold-colored panel face
has a stylish appeal. Even in the smallest detail,the C-275V exudes an atmosphere of sheer classwhich makes this analog preamplifier a joy to own
and rapture to listen to.

Balanced output stage with bridged feedback
In balanced signal transmission, two identicalsignals are transmitted simultaneously with inverted
phase and combined at the receiving end, thereby
canceling out common-mode noise and interference.
This principle is one of the requirements for truly
high-quality sound.
The principle of balanced sound transmission isshown in Figure 4. The outputs of the two amplifiers
are connected to form a cross-feedback loop, which
sends the symmetrical (+) and (–) signals with low
impedance to the next stage. The signals are
isolated from the ground line, resulting in an idealbalanced circuit. Even if one side of the output isgrounded, both amplifiers continue to operate, andthe output voltage does not change.

(Option)Discrete line amplifier for optimum soundThe line amplifier is a pure complementary pushpull circuit. It is built from discrete components andemploys the superior current feedback principle.
Phase compensation can be kept to a minimum,
resulting in realistic ambience.
Printed circuit boards made from Teflon with low
dielectric constant and low loss
The printed circuit boards for the signal-carrying
circuits are made of Teflon, a glass fluorocarbon
resin material. Teflon has a stable, low dielectric
constant as well as superior heat resistance,
excellent high-frequency characteristics, and manyother desirable properties. As a result, signal purity
is enhanced and there is a drastic improvement inperceived S/N ratio.
* Teflon is a registered trademark of DuPont USA.

Complete mono construction with separatetransformers for left and right channels
The power supply of the C-275V employs a dualmono approach with separate power transformers
and filtering capacitors for the two stereo channels.
Each unit amplifier is equipped with a wide-range
low-impedance voltage regulator to eliminate
possible interference between stages.
Tone controls use summing active filters forhighest sound quality

Fig. 1 Block diagram of C-275V (one channel)

The tone control circuitry in the C-275V wasspecially
designed withInput
Outputsumming
active filterssuch as foundin high-quality
g r a p h i ce q u a l i ze r s .
Figure5illustrates theoperation
principle ofthis circuit. The flat signal is passed straight through,and only when an adjustment is required, thecharacteristics are created at F1 and F2 and added
to the signal, thereby producing the desired change.
This design provides efficient control without
degrading signal purity.
Vibration-free design with unit amplifiers inaluminum enclosures fastened to 8-mm
hardened aluminum chassis

Logic-controlled relays for signal switchingassure high sound quality and long-term
reliability

resistance and outstanding long-term reliability.

The use of logic-controlled relays at strategic
locations makes it possible to keep signal paths
extremely short. The relays used in the C-275V are
high-performance hermetically sealed types as usedin professional communication applications. The
contacts are twin crossbar types plated with goldand silver palladium alloy, for minimum contact

n Volume control designed for sonic purity

The C-275V has four unit amplifiers, two each forthe line input and line output in each channel. Each
unit is powered by its own local voltage regulator
circuitry, and is housed in a strong aluminum
enclosure, to prevent interference between units.

Hermetically sealed relays connected
directly to gold-plated input/output jacks

n Mother PCB with gold-plated
copper paths supports the four
unit amplifiers (line andbalanced amplifiers), as wellas filtering capacitors andperipheral circuitry.
Unit amplifier in thick aluminum housing

n Remote commander
RC-26
allows volume
control and input
source selection*

Photo shows the amplifier with
optional phono equalizer unit
AD-275V installed

Other featuresn Supplied remote commander for volume
adjustment and program source switchingn Dedicated headphone amplifier for superiorsoundn Versatile array of functions
m Tape recorder facilities with monitor switch andcopy switch
m Output phase selector button
m Loudness compensator with three selectablecharacteristicsm Subsonic filter removes ultra low frequency
noiseGuaranteed Specifications

Dedicated Phono Equalizer Unit AD-275V
In its default configuration, the C-275V is a line preamplifier for reproduction of CDs andsimilar sources. Audiophiles with a collection of analog records will welcome the capability
to install the dedicated phono equalizer unit AD-275V in a rear-panel slot, which allows
reproduction of analog discs with sonic quality of the highest caliber.
The unit uses printed circuit boards made from Teflon material (glass fluorocarbon resin)
and is housed in a sturdy aluminum case for complete protection against any externalinterference. Highly reliable DIN standard connectors make the shortest possible
connection between input and amplification circuits. This assures outstanding S/N ratio.
The circuit diagram of the unit is shown below. Dedicated input stages are provided for
MM and MC cartridges. To get the best out of each pickup type, the MC input impedance
can be switched in three stages (10/30/100 ohms). MM input impedance is fixed to 47kilohms. To match the output of the cartridge, MC gain can be set to 60 or 66 dB.
**The AD-275V can only be used in the Accuphase models C-275 or C-275V.
The phono equalizer unit AD-275 designed for the Accuphase model C-275
can also be used in the C-275V.

**

Guaranteed specifications are measured according to EIA standard RS-490. AD stands for "Analog Disc".
Specifications are shown for phono equalizer unit AD-275V installed.

m Frequency Response

BALANCED/UNBALANCED:AD INPUT:m Total Harmonic Distortion

Input
AD : MMAD : MC/60 dB
AD : MC/66 dB
BALANCEDUNBALANCED

m Output Voltage,
Output Impedance+0, –3.0 dB+0, –0.2 dB–0.2 dB

Sensitivity
For rated output
For 0.5 V output
4.0 mV
1.0 mV
0.25 mV
0.063 mV
0.125 mV
0.0315 mV
252 mV63 mV
252 mV
63mV

BALANCED OUTPUT:UNBALANCED OUTPUT :TAPE REC:m Signal-to-Noise Ratio

47 kilohms
10/20/100 ohms
10/20/100 ohms
40 kilohms
20 kilohms

2 V, 50 ohms, XLR type connectors
2 V, 50 ohms, RCA type phono connectors
252 mV, 200 ohms (with AD input)

Input shorted, IHF-A weighting
S/N ratio at rated output
90 dB
79 dB
75 dB
114 dB
116 dB

Input

Input Impedance

EIA S/N
91 dB
84 dB
84 dB
96 dB
96 dB

m Maximum Output Level(0.005% THD, 20 - 20,000 Hz)

BALANCED OUTPUT :UNBALANCED OUTPUT :TAPE REC :6.0 V, XLR type connectors
6.0 V, RCA type phono connectors
6.0 V (with AD input)

m Maximum AD Input Level(0.005% THD)MM INPUT :MC [60/66 dB] INPUT :125 mV
8 mV/4 mVOutput

m Minimum Load Impedance BALANCED/UNBALANCED OUTPUT :TAPE REC :600 ohms
10 kilohms

m GainBALANCED/UNBALANCED INPUTBALANCED/UNBALANCED INPUTAD [MM] INPUTAD [MM] INPUTAD [MM] INPUTAD [MC: 60/66 dB] INPUTAD [MC: 60/66 dB] INPUT

m Loudness Compensation

1: +3 dB (100 Hz)

2: +6 dB (100 Hz)

3: +6 dB (100 Hz), +6 dB (20 kHz)m Tone Controls

Turnover frequency and adjustment range

BASS :
300 Hz ±10 dB (50 Hz)
TREBLE : 3 kHz ±10 dB (20 kHz)m Subsonic Filter

25 Hz -12 dB/octave

m Attenuator Characteristics–6 dB, –20 dB, –30 dB

m Headphone Jack

Suitable impedance: 4 - 100 ohms

m Power Requirements

120V/230 V (Voltage as indicated on rear panel) AC, 50/60 Hz

m Power Consumption

25 watts

m Maximum DimensionsWidth 475 mm (18-11/16"), Height 150 mm (5-7/8"), Depth 404 mm (15-7/7")

m Weight

21.7 kg (47.8 lbs) net, 27.2 kg (60.0 lbs) in shipping carton

m Supplied RemoteCommander RC-26

Remote control principle :infrared pulse
Power supply :3 V DC (IEC R6 batteries x 2)
Maximum Dimensions : Width 66 mm (2-5/8"), Height 175 mm (6-7/8"), Depth 20 mm (13/16")
Weight :190 g (419 lbs) (including batteries)

Equalizer
elements

DC servo amplifiern Circuit diagram of phono equalizer unit AD-275V (one channel)

n Phono equalizer amplifier assembly (one channel)

300,000 Hz
20,000 Hz
20,000 Hz

0.005% (for all inputs)

m Input Sensitivity, Impedance

AD : MMAD : MC/60 dB
AD : MC/66 dB
BALANCEDUNBALANCED

Input

3 20 20 -➝ BALANCED/UNBALANCED OUTPUT :➝ REC OUTPUT:➝ BALANCED OUTPUT :➝ UNBALANCED OUTPUT :➝ REC OUTPUT :➝ BALANCED/UNBALANCED OUTPUT :➝ REC OUTPUT :

18 dB
0 dB
54 dB
54 dB
36 dB
78/84 dB
60/66 dBn REAR PANEL (Photo shows the amplifier with optional phono equalizer unit AD-275V installed)n FRONT PANEL

HH

Input selector
LINE-BAL LINE 3 LINE 2 LINE 1CD-BAL
CD TUNERAD (OP)
Loudness compensator selector
Function LED indicators
Balance control
Volume control
Power switch
Recording output/tape monitor selector
REC OFF SOURCE TAPE 1 TAPE 2

Output ON/OFF button
Output phase selector button
Subsonic filter
Tone control switch /BASS/TREBLE controls
Tape copy buttons
OFF1➝22➝1
Stereo/mono selector button
Attenuator selector
OFF –6 dB –20 dB –30 dB

Loudness compensator ON/OFF switch
Headphone jack
AD (Analog Disc) input
AD ground terminal
Equalizer gain selector
MMMC/60 dB
MC/66 dB
MC cartridge load impedance selector
10 Ω30 Ω100 ΩLine inputs
CDTUNER
LINE 1,2,3

Tape recorder REC/PLAY jacks
Unbalanced outputs
Switched AC outlets H
CD/LINE balanced inputs
a GND
b Inverted [–]c Non-inverted [+]Balanced outputs (2 sets)
a GND
b Inverted [–]c Non-inverted [+]AC power connectorH(for supplied power cord)

Remarks
H This product is available in versions for 120/230 V AC. Make sure that the voltage shown on the rear panel matches the AC line voltage in your area.
H The shape of the AC inlet, plug of the supplied power cord, and AC outlet depends on the voltage rating and destination country.
H These unswitched AC outlets may not be supplied depending on the safety standards or regulations applicable in the particular country to where the unit is destined.

n Supplied accessories m AC power cordm Audio cables with RCA plugs
m Remote commander RC-26* Specifications and design subject to change without notice for improvements.

http://www.accuphase.com/

PRINTED IN JAPANE0010 851-0167-00 (AD1)