Page 1
m Separate MM/MC amplifi er circuitry ensures ultra low noise m Highly precise
equalization with only ±0.3 dB RIAA deviation
three settings for MM and six settings for MC
up to 70 dB
and unbalanced analog outputs
m Three analog player inputs with separate settings memory m Balanced
m Versatile impedance switching with
m Gain switching enables high gain of
m Polarity selector for balanced outputs
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The Ultimate Phono Equalizer Amp — Separate circuitry for MM and MC
ensures ultra low noise performance and outstanding RIAA precision. Versatile
load impedance selector with three settings for MM and six settings for MC
brings out the best in every cartridge. Subsonic fi lter, and high gain capability
of up to 70 dB with gain switching. Three analog player inputs with separate
settings memory for each input.
The analog phono record is experiencing a quiet boom
among discerning music lovers. It goes without saying that
a phono equalizer of high quality is essential to extract
the enormous richness of sonic information engraved
on vinyl records. Furthermore, the selection of tonearm,
cartridge and other parts of the playback system requires
a thorough understanding of audio fundamentals. This is
a fi eld where some investment of time and effort can yield
immensely satisfying results.
Accuphase has gained considerable expertise in designing
and building phono equalizers, either integrated in
preamplifi ers or available as option (AD-2810 and AD-20).
In response to the wishes of audiophiles worldwide, we
have now developed the C-27 as a high-end standalone
phono equalizer amplifier, capable of exploring the
possibilities of the analog disc to the fullest.
Because the output signal level of a record player is
extremely low, high-gain amplifi cation is required before
supplying the signal to subsequent stages. Distortion
and noise should be kept to an absolute minimum, and
excellent linearity from low to high frequencies is also a
must. In the C-27, these goals are achieved by employing
completely separate amplifi er sections for MM and MC,
each with optimized circuit topology and strictly selected
parts for no-compromise performance. S/N ratio, THD,
high-frequency characteristics, linearity and all other
parameters approach the ideal in performance. What’s
more, the C-27 is perfectly equipped to accommodate a
wide range of cartridge output voltage ratings and load
impedance requirements. To ensure optimum matching,
three different settings for MM and six different settings
for MC can be selected.
Designed to raise the bar for phono equalizer amplifi ers,
the C-27 will bring out the characteristics and musical
qualities of any phono cartridge to optimum effect,
providing pure music enjoyment from those legendary
analog discs.
C-27 Functions and Features
■
Separate MM/MC amplifi er confi guration ensures ultra low noise
■ Highly precise equalization: RIAA deviation only ±0.3 dB
■ Monaural construction with separate toroidal power transformers
and separate equalizer boards for left and right channel
■ Versatile impedance switching options
MM
1k, 47k, 100k
MC
3, 10, 30, 100, 300, 1k
Load impedance indicators Load impedance
■ Subsonic fi lter
(10 Hz, -12 dB/octave)
■ Gain switching enables high
gain of up to 70 dB
Subsonic fi lter and
gain indicators
■ Equalizer PCBs made from Tefl on* (glass fl uorocarbon resin)
with low dielectric constant and low loss
* Tefl on is a registered trademark of DuPont USA.
■ Gold-plating of all major parts in signal path
■ Three inputs for analog players or tonearms, each with a separate
memory for MM/MC, load impedance, gain, subsonic fi lter and
other settings
(LEDs show selection status)
Input selector
Filter
button
selector
Gain selector
button
MM/MC indication
Filtering capacitors
MM/MC
selector
Power transformer
LEFT
CHANNEL
LEFT
CHANNEL
INPUTS
RIGHT
CHANNEL
GND
GND
GND
MM Amplifi er Section
+
IMPEDANCE
SELECTOR
1kΩ
47kΩ
1
2
3
INPUT
SELECTOR
MM-MC
100kΩ
IMPEDANCE
SELECTOR
3Ω
10Ω
30Ω
100Ω
300Ω
1kΩ
IMPEDANCE
LOAD
MM
AM
P
–
RIAA EQUALIZER
NETWORK
DC SERVO
GAIN
MC Amplifi er Section
+
MC
AMP
–
RIAA EQUALIZER
NETWORK
DC SERVO
GAIN
GAIN
Same as LEFT CHANNEL
■ Two separate
board assemblies for
left and right channel,
using Tefl on substrate and
carrying dedicated MM and
MC amplifi ers, phono equalizer
amplifi ers, and logic relays for signal
switching to ensure shortest possible
paths between inputs and outputs.
+
–
SUBSONIC
R
FILTE
FILTER
–1
FEEDBACK
NETWORK
–1
FEEDBACK
NETWORK
BALANCE
CONNECTION
UNBALANCE
BALANCED
D
LEFT
CHANNEL
OUTPUTS
C-27 Circuit Diagram
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Completely separate MM and MC sections
One of the biggest challenges for a phono equalizer amp is the problem of noise. How to achieve high S/N ratio is a crucial point. In order to precisely
match the circuit confi guration to the different requirements of MM and MC cartridges, the C-27 features separate sections employing purpose-selected
components and optimized operating points. This uncompromising approach results in outstanding S/N ratio, minimum distortion, and excellent frequency
response characteristics. Amplifi er performance fi nally approaches ideal levels.
MM amplifi er section
The MM section must provide a high impedance input while
also reducing residual noise. To achieve this, FET devices
were selected for the initial stage. The circuit confi guration
is defi ned as “3-parallel low noise FET buffer amplifi er” +
“6-parallel ultra low noise transistor differential push-pull
circuit”.
MC amplifi er section
The MC section must provide low internal
impedance over a wide range to properly
handle the output voltage of MC cartridges,
which is a level of magnitude lower than
that of MM cartridges. Residual noise of
the amplifi er therefore needs to be kept
to an absolute minimum. This is achieved
by using an
transistor differential push-pull circuit
guarantee high S/N ratio.
“
8-parallel ultra low noise
”
to
+
B
Q
17
Q
21
Q
Q
1
Q
3
5
Q
7
Q
9
Input Input
Q
Q
Q
2
Q
4
6
8
Ultra low noise transistor differential
push-pull circuit in 6-parallel confi guration
Q
10
Low noise FET buffer amplifi er in 3-parallel confi guration
Q
Q
11
Q
13
15
Q
19
Q
23
Output Output
Q
Q
12
Q
14
16
Q
Q
20
Q
18
24
Q
22
-
B
Equalizer Components
DC Servo Amplifi er
Gain Control
MM Amplifi er Section
Circuit Diagram
Q
1
Q
2
Ultra low noise transistor differential
push-pull circuit in 8-parallel confi guration
Q
3
Q
4
MC Amplifi er Section
Circuit Diagram
Q
33
Q
34
Q
37
Q
35
Q
36
Q
38
Equalizer Components
DC Servo Amplifi er
Gain Control
+
B
Q
39
Q
40
-
B
Page 4
Other Functions and Features
■ Balanced and unbalanced analog outputs
■ Side panels with elegant persimmons wood fi nish
Input jacks and ground connector
High-reliability parts selected for sound quality
Balanced output connectors
Polarity selector for balanced outputs
● In the factory default condition, the
switch is set to the left position (pin
+) as shown in the photo.
Only change the switch position if the
●
connected preamplifi er or integrated
amplifi er requires the (pin +) setting.
Performance Graphs
[dB]
10
8
6
4
2
0
-2
-4
-6
-8
-10
10 100 1k 10k 100k
Input voltage vs. THD characteristics (MM) Input voltage vs. THD characteristics (MC)
Frequency [Hz] Frequency [Hz]
RIAA deviation (MM amplifi er) RIAA deviation (MC amplifi er)
[dB]
10
8
6
4
2
0
-2
-4
-6
-8
-10
10 100 1k 10k 100k
■ Front panel
[Guaranteed specifi cations are measured according to EIA standard RS-490.]
● RIAA Deviation MM 10 - 100,000 Hz ±0.5 dB
20 - 20,000 Hz ±0.3 dB
C-27 Guaranteed Specifi cations
MC 10 - 100,000 Hz ±0.3 dB
● Total Harmonic Distortion 0.005%
● Gain *INPUT BALANCED/UNBALANCED OUTPUT
GAIN button OFF (Normal) MM: 30 dB
MC: 60 dB
GAIN button HIGH MM: 40 dB
MC: 70 dB
● Input Sensitivity (at rated output: 1 kHz, 2 V)
MM 30 dB: 63.2 mV
40 dB: 20.0 mV
MC 60 dB: 2.0 mV
70 dB: 0.63 mV
● Maximum Input Voltage (1 kHz, THD 0.005%)
MM 30 dB: 300 mV
40 dB: 95 mV
■ Rear panel
MC 60 dB: 9 mV
70 dB: 2.9 mV
● Maximum Output Level (THD 0.002% 20 - 20,000 Hz)
BALANCED/UNBALANCED OUTPUT: 8.0 V
● Input Impedance MM settings: 1 kilohm, 47 kilohms, 100 kilohms
MC settings: 3 ohms, 10 ohms, 30 ohms, 100 ohms,
300 ohms, 1 kilohm
● Rated Output and Output Impedance
BALANCED OUTPUT 2 V 50 ohms
UNBALANCED OUTPUT 2 V 50 ohms
● S/N Ratio
S/N ratio at rated output
MM, 30 dB 110 dB
MM, 40 dB 102 dB
Subsonic fi lter indicator
Gain indicator
Load impedance indicator
For MM: 1k, 47k, 100k
For MC: 3, 10, 30, 100, 300, 1k
MM-MC indicator
Input selector 1, 2, 3
MM-MC selector
Player input jacks 1, 2, 3
Player ground connectors
Unbalanced output jacks
Balanced output connectors
Balanced connection polarity selector
AC power connector
Power switch
Load impedance selector
Subsonic fi lter button
Gain selector
Remarks
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.
The shape of the AC inlet and plug of the supplied power cord depends on the voltage rating and destination country.
n Supplied accessories:
m
AC power cord
m
Audio cables with plugs (1 m)
m
Cleaning cloth
MC, 60 dB 98 dB
MC, 70 dB 90 dB
●
Minimum Load Impedance
BALANCED/UNBALANCED OUTPUT: 10 kilohms
● Crosstalk –90 dB or less (10 kHz)
●
Residual Noise (A-weighted)
MC : 25 V or less
GAIN button HIGH MM : 16 V or less
MC : 63 V or less
GAIN button OFF (Normal) MM : 6 V or less
● Subsonic Filter –12 dB/octave, 10 Hz
● Power Requirements AC120 V/230 V (Voltage as indicated on rear panel)
50/60 Hz
● Power Consumption 35 W
● Maximum Dimensions Width 465 mm (18-5/16")
Height 121 mm (4-3/4")
Depth 405 mm (15-15/16")
● Mass 14.5 kg (32.0 lbs) net
20.0 kg (44.1 lbs) in shipping carton
Input terminal
Input shorted (A weighting)
m
Specifi cations and design subject to change without notice for improvements.
http://www.accuphase.com
K0850Y PRINTED IN JAPAN 851-0183-00 (AD1)
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