● Separate left/right MC head amplifier and equalizer circuitry ensures ultra low noise● Highly precise equalization with only ±0.3 dB RIAA deviation ● Versatile impedance
switching with six settings for MC and three settings for MM ● Gain switching enableshigh gain of up to 70 dB ● Three analog player inputs with separate settings memory● Balanced and line analog outputs ● Polarity selector for balanced outputs

The Ultimate Phono Equalizer Amp — Separate circuitry for left and right MC head amplifierand equalizer amplifier using latest devices ensure ultra low noise performance andoutstanding RIAA precision. Versatile load impedance selector with six settings for MC andthree settings for MM brings out the best in every cartridge. Subsonic filter, and high gain
capability of up to 70 dB for MC and up to 40 dB for MM with gain switching. Three analog
player inputs with separate parameter memory for each input.
Renewed interest in the analog phono record has
led to a rising boom among discerning music
lovers. The analog record is a medium where
careful selection of individual components such as
the tone arm, cartridge and phono equalizer amp,
along with knowledgeable setup and fine-tuning canyield immensely satisfying results in terms of soundquality and music enjoyment.
Ever since its beginnings, Accuphase has been
accumulating considerable expertise in the domainof analog records. In 2008, this culminated in therelease of the Phono Amplifier C-27, a product thatastonished the audio world with its amazingly low
S/N ratio and impeccable sound. The C-37 now
sets the bar even higher. Designed to match theAccuphase 40th anniversary models C-3800 andC-2820, the C-37 is a no-compromise standalone
phono equalizer amplifier incorporating latest circuitdesign and utilizing materials and parts with optimalsonic qualities, making it capable of exploring thepossibilities of the analog disc to the fullest.
Because the output signal of a record player isextremely low, the voltage must be amplified to alevel that is suitable for the subsequent stages. To
perform this task, the phono amplifier must
accurately handle the minute signal while keeping
distortion and noise to an absolute minimum overthe entire range from low to high frequencies. In theC-37, these goals are achieved by employing
completely separate MC head amplifier and■ Dual mono construction with left/right separate
toroidal power transformers and left/rightseparate MC head amplifier and equalizer
sections.
■ Equalizer PCBs made from glass fluorocarbon
resin with low dielectric constant and low losses.
■ Gold-plating for all major parts in signal path.

FilterbuttonMC/MMselector

Load impedance
selector

equalizer sections, and keeping the left and rightchannels also separate. Circuit topology isdesigned to optimally match the characteristics ofMM and MC cartridges respectively, realized withultra low noise transistors. This enables the C-37 to
fully bring out the characteristics and sonic qualities
of any phono cartridge, allowing the listener toexplore the legendary musical depth of analog
discs.
In terms of physical appearance, the gold-coloredpanel face and side panels of real wood withnatural grain finish exude an aura of refined
elegance, making the C-37 a perfect match for theC-3800 as well as other models such as the C-2820
or C-2420.

Gain selector
buttonMC3Ω, 10Ω, 30Ω, 100Ω, 300Ω, 1kΩ

MM1kΩ, 47kΩ, 100kΩ

Power transformer

Filter capacitors■ Gain switching enables high gain of up to 70 dB.
Load impedance indicators■ Highly precise equalization: RIAA deviation only
±0.3 dB.
■ Versatile load impedance switching options
with 6 settings for MC and 3 settings for MM.
■ Three inputs for analog players or tone arms,
each with a separate memory for MC/MM, load
impedance, gain, subsonic filter and othersettings.
■ Subsonic filter (10 Hz, -12 dB/octave).

Input connectors andground terminal
Input selectorBalanced outputconnectors

Subsonic filter andgain indicators■ Two sets of analog outputs for balanced andLine connections.

［ dB］ 5Phase selector

0−5−10■ Phase selector for balanced outputs.

−15■ Elegant side panels of real wood with naturalgrain finish.
■ Top plate designed to ensure uniform thermal
diffusion while suppressing chassis vibrations.

−20−25−30−35−40

1

10100
1k
Frequency ［Hz］

10k100k

Subsonic Filter Characteristics
Parts selected for high sound quality and reliability

Block Diagram
GAIN 30 dBLEFT
CHANNELGAIN 30 / 40 dBGAIN 0 dB
LINE

MC HEAD AMPLIFIER

1EQUALIZER AMPBALANCED – OUTPUT AMPLIFIER

GND
LOAD
IMPEDANCELEFT
CHANNELINPUTS

23Ω

GND

10Ω+HEADAMP

EQUALIZERAMP

1kΩ
47kΩ

100Ω

GND+––30Ω

3LOAD
IMPEDANCE300Ω

GAIN

RIAA EQUALIZERNETWORK＋−−＋LEFT
CHANNELOUTPUTSSUBSONICFILTERBALANCED

100kΩ
DC SERVO

1kΩ−GAIN＋BALANCED + OUTPUT AMPLIFIER

INPUT

RIGHT
CHANNEL

MC/ MM

LOAD
IMPEDANCEGAIN

Same as LEFT CHANNELFILTERBALANCED
CONNECTION

■ Two separate board
assemblies for left and rightchannel, using glass fluorocarbon resin
substrate and carrying MC head amplifier, phonoequalizer amplifier, and logic relays for signal switchingto ensure shortest possible paths between inputs and outputs.

Completely separate left/right MC head amplifier and equalizer sections
One of the biggest challenges for a phono equalizer amp is the problem of noise. How to achieve high S/Nratio is a crucial point. The C-37 therefore features separate MC head amplifier and equalizer sections forthe left and right channel, in order to precisely match the circuit configuration to the different requirements ofMC and MM cartridges. Employing purpose-selected components and optimized operating points, thisuncompromising approach results in outstanding S/N ratio, minimum distortion, and excellent frequency
response characteristics. Amplifier performance finally approaches ideal levels.

MC Head Amplifier

Equalizer Amplifier
The amplifier for MM cartridges must provide a high impedance
input while also reducing residual noise. To achieve this, aMC cartridges have an output signalthat is a level of magnitude lower thanthat of MM cartridges. Residual noiseof the amplifier therefore needs to be
kept to an absolute minimum. In theC-37, this is achieved by using an MC
head amplifier optimized for this type of cartridge, with a "3-parallel ultra low
noise transistor differential circuit" as shown below to guarantee high S/N ratiothat exceeds even the C-27 by 2 dB.

sophisticated equalizer amplifier to suit the requirements of MM
cartridges was designed. FET devices (field effect transistors)
ideal for high impedance applications are used in the initialstage, and the circuit as shown below is configured as a"3-parallel low noise FET buffer amplifier" + "6-parallel ultra lownoise transistor differential push-pull circuit".

+B+B1
Q17Q7Q8Q7Q10Q1Q3Q9Q5Q 11Q 13Q 15Q23Q12Q19

OutputInput
Q1Q3Q5Q2Q4+B2Q21Q6Output

Input
Q2Q4Q6Q8Q 10Q12Q 14Q 16
Q24Q13Ultra low noise transistors in3-parallel differential circuit
configuration

Q9Q20Q11Q18–B1–BGain Control

Q22

Ultra low noise transistor differential
push-pull circuit in 6 -parallel configuration

Low noise FET buffer amplifier in 3 -parallel configuration

EqualizerComponents

DC Servo Amplifier

Gain Control

MC Amplifier Circuit Diagram
Ultra low noise transistors

Equalizer Amplifier Circuit Diagram–B2

Performance Graphs［ dB］
10［ dB］
108866442200−2−2−4−4−6−6−8−8100

1kFrequency ［Hz］

10k

100k

Total Harmonic Distortion in %Load Impedance:
EIA Std. Dummy
Gain at 1kHz
60.00 dB
Maximum Input Voltage
20Hz : 1.16mV
1kHz : 10.26mV
20kHz : 78.83mV

To CD, LINE, AUX or similar input

1001k
Frequency ［Hz］

10k

Model
: C-37
Serial:Date:
Input:Output: LineComment :MM 30dB 47k Lch

0.01

Load Impedance:
EIA Std. Dummy

0.001

Gain at 1kHz
30.00 dB
Maximum Input Voltage
20Hz :
0.03V
1kHz :
0.30V
20kHz :
2.46V

0.0001

100k

1mV

10mV

Audio cable with plugs (supplied)

Balanced audio cable

0.01

0.001

0.0001:20Hz:1kHz:20kHz: 20Hz: 1kHz: 20kHz0.00001
100uV

Select oneof these twoconnection
methods

0.1

THD vsInput Voltage

Accuphase Lab.Inc.

Groundleads

RIAA deviation (MM equalizer amplifier)

0.1

Model: C-37
Serial:Date:
Input:
Output:Comment :MC 60dB

Preamplifier or
integrated amplifier

Groundlead−1010

RIAA deviation (MC head amplifier)

THD vs
Input Voltage

Analog record players

Total Harmonic Distortion in %−1010Connection Example

1V

100mV

Input Voltage

C-37
0.00001
1mV

10mV

Accuphase Lab.Inc.

Input voltage vs. THD characteristics(MC head amplifier)

100mV

1V

＊Use shielded audio cable(dual-core shielded forbalanced connection).

10VInput Voltage

Input voltage vs. THD characteristics(MM equalizer amplifier)◆ Front panel

AC power cord (supplied)

C-37 Guaranteed Specifications[Guaranteed specifications are measured according to EIA standard RS-490.]

e Load impedance indicator

For MC: 3Ω, 10Ω, 30Ω, 100Ω, 300Ω, 1kΩ
For MM: 1kΩ, 47kΩ, 100kΩ

w Gain indicatorq Subsonic filterr MC/MM indicator

indicatort Input selector
1/2/3●RIAA Deviation

10 ‑ 20,000 Hz
10 ‑ 20,000 Hz±0.3 dB±0.3 dB●Total Harmonic Distortion (1 kHz, at rated output)

0.005%●Gain

MCMM＊INPUT → BALANCED / LINE OUTPUT
GAIN button OFF (Normal)

MC:
MM:
MC:
MM:

GAIN button HIGH
● Input Sensitivity (at rated output: 1 kHz, 2 V)
MC

60 dB: 2.0 mV
70 dB: 0.63 mV
30 dB: 63 mV
40 dB: 20 mV

MM●Maximum Input Voltage (1 kHz, THD 0.005%)
MCy Power switch
u Load impedance selector●Maximum Output Level (THD 0.002% 20 ‑ 20,000 Hz)
BALANCED / LINE OUTPUT: 8.0 Vo Gain selector

i Subsonic filter button● Input Impedance◆ Rear panel!1 Player input jacks !2 Line output
1/2/3jacks

60 dB: 9.0 mV
70 dB: 2.9 mV
30 dB: 300 mV
40 dB: 95 mV

MM!0 MC/MM selector!3 Balanced output connectors

MC settings: 3 ohms, 10 ohms, 30 ohms, 100 ohms,300 ohms, 1 kilohm
MM settings: 1 kilohm, 47 kilohms, 100 kilohms●Rated Output and Output Impedance
BALANCED OUTPUT
LINE OUTPUT

2V
2V

MC: 60 dB
MC: 70 dB
MM: 30 dB
MM: 40 dB

Input shorted (A weighting)
S/N ratio at rated output
100 dB
91 dB110 dB
102 dB● Minimum Load Impedance

BALANCED / LINE OUTPUT:● Crosstalk−90 dB or less (10 kHz)● Residual Noise (A-weighted) GAIN button OFF (Normal)
GAIN button HIGHterminals!6 AC power connector★

!5 Balanced output

connection phaseselector■ Supplied accessories:

AC power cord
● Audio cables with plugs(equivalent to ASL-10, 1 m)
● Cleaning cloth

50 ohms
50 ohms●S/N Ratio, Input-converted NoiseInput terminal!4 Analog player ground

60 dB
30 dB
70 dB
40 dB

10 kilohms
MC: 19 µV or less
MM: 6 µV or less
MC: 59 µV or less
MM: 16 µV or less●Subsonic Filter−12 dB/octave, 10 Hz●Power Requirements

AC120 V/220 V/230 V, 50/60 Hz(Voltage as indicated on rear panel)●Power Consumption

20 W●Maximum Dimensions

Width 465 mm (18.31”)
Height 114 mm ( 4.49”)
Depth 407 mm (16.02”)●Mass

14.5 kg (32.0 lbs) net
20.0 kg (44.1 lbs) in shipping carton●Remarks
This product is available in versions for 120/220/230 V AC. Make sure that the voltage shown on the rear panel matches the AC line voltage in your area.
230 V version has an Eco Mode that switches power off after 120 minutes of inactivity.
The shape of the AC inlet and plug of the supplied power cord depends on the voltage rating and destination country.

●The specifications and appearance of this product are subject to change without notice.

5年間保証

K1405Y PRINTED IN JAPAN 850-2189-00（B1）