
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

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

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

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)