Accuphase C-3850 User Manual

● Revolutionary low-noise "Balanced AAVA Volume Control" ● High-rigidity,

high-accuracy volume knob sensor mechanism ● Separate high-efficiency
toroidal power transformers for left and right channels ● Selectable preamp
gain ● Fully modular construction with separate left/right units for each amplifier
stage ● Logic-controlled relays for shortest signal paths ● Independent phase
selection for each input position ● Printed circuit boards made from glass cloth
fluorocarbon resin ● Massive wood cabi net with natural grain finish

The Ultimate Analog Preamplifier — Balanced AAVA, the supreme volume control

system from Accuphase, provides incredible smoothness and complete mastery over the

music reproduction process. Outstanding signal/noise ratio prepares the stage for the

source to emerge with breathtaking realism, conveying a wealth of acoustic detail such

as hardly ever experienced before. The C-3850 represents the pinnacle of 45 years of

Accuphase excellence in analog preamplifiers.

Having been founded in 1972, Accuphase commemorated
its 40th anniversary by releasing a next-generation beacon
model, the Precision Stereo Preamplifier C-3800. It marked
a major milestone and was highly lauded by audiophiles
around the world as a tour de force in technological
excellence, performance, and sound quality. The new
Precision Stereo Preamplifier C-3850 continues the
challenge and raises the bar even further, bringing
together the entire wealth of preamplifier know-how gained
by Accuphase over the years. In construction as well as
circuit design, it incorporates latest technology realized
with components selected through a thorough review
process including extended listening tests. The result is an
audio instrument that admits no compromise in the pursuit
of peerless performance for musical mastery.
Conventional volume controls attenuate the input signal by

Balanced AAVA (Accuphase Analog Vari-gain Amplifier) Volume Control

High Voltage
Current Feedback
Amplifier

Conversion into current
with 16 weighting
stages (1/2 - 1/2

V- I Converter

1

−

2

1

−

2

2

1

−

8

2

1

−

15

2

1

−

16

2

16

)

4-parallel

2-parallel

16 current switches

16

2

= 65,536

possible combinations

introducing a resistance (either using a rotary variable
resistor or fixed resistors) in the signal path, and then
amplifying the result. This makes it inevitable that–along
with attenuation–information will be lost and noise will
increase at the lower volume level settings that are
normally used. By contrast, AAVA does not "turn down" the
volume in the ordinary sense. Rather, it switches a
combination of V-I amplifiers as required in order to directly
change the amplifier gain and thereby achieve the desired
volume. This revolutionary approach eliminates impedance
changes as well as adverse effects from noise and other
factors. Because there is almost no increase in noise, S/N
ratio does not suffer at any listening level including the
important moderate volume settings. Frequency response
remains uniform and sound quality always maintains its full
excellence. The C-3850 features a further evolved version

Operation Principle of

Balanced AAVA in C-3850

I-V Converter

Reconversion of current into voltage

＋

Current values
are added

LEVEL DISPLAY

+ OUTPUT+ INPUT

The musi c signa l is converted into 16 types of weighted current by V-I
(voltage-to-current) converting amplifiers, as shown in the illustration below.
The 16 currents are turned on or off by 16 current switches, and the
combination of switch settings determines the overall current. The resulting
current forms a variable gain circuit that adjusts the volume of the music signal.
The respective currents are combined and converted back into a voltage by an
I-V (current-to-voltage) converter before being sent to the subsequent stage.

Current
ratio

of this principle, called "Balanced AAVA", with two AAVA
circuits driven in a parallel balanced configuration. This
results in ideal volume control behavior from balanced
input to balanced output. In addition, the volume knob and
sensor mechanism fashioned with utmost precision from a
single highly rigid aluminum block provides silky smooth
operation with excellent tactile feel, and also improves the
quietness of motor-driven operation. The entire path for all
signals from the input connectors to the outputs is fully
balanced, and signal purity is further elevated by the use of
ultimate-quality parts and materials, ensuring electrical
characteristics and sonic excellence of the highest order.
With its no-holds-barred use of resources, and its bold
realization of latest circuit design, the C-3850 is an analog
preamplifier that redefines the state of the art and points
the way towards the future.

AAVA Operation Principle

0.5

Graphic representation of 16 types of V-I
converter amplifiers and resulting currents

0.4

0.3

0.2

Balanced

Input

–

INPUT

High Voltage
Current Feedback
Amplifier

CPU controls current on/off
switches so that volum e
level matches knob position

V- I Converter

1

−

16

2

1

−

15

2

1

−

8

2

1

−

2

2

2-parallel

1

−

2

4-parallel

CPU

VOLUME

Volume knob is turned and volume
level position is detected

Current values
are added

＋

I-V Converter

Reconversion of current
into voltage

Balanced

Output

–

OUTPUT

0.1

0

1

1

−

−

2

2

2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

The se V -I con ver ter s h and lin g m inu te

cur rent le vel s e nab le ext rem ely

del icat e v olu me con tro l.

1

1

1

1

1

1

1

−

−

−

−

3

4

5

6

2

2

2

2

1

−

−

−

−

7

8

9

10

2

2

2

2

1

1

1

1

1

−

−

11

12

2

2

1

−

−

−

−

13

14

15

16

2

2

2

16 types of V-I
converters

2

–Extruded from solid aluminum block –

High-rigidity volume sensor construction

ATTENUATORBALANCE

★Cut away mode l of vol ume sens or m echa nism

■

Upper two V-I converter amplifiers feature a special
configuration, with 4-parallel operation for the topmost and
2-parallel operation for the second level, resulting in lower
impedance and an amazing S/N ratio improvement of 2 dB.

■

No more left/right tracking differences or crosstalk.

■

Amplifier display shows accurate gain as numeric
indication.

■

High S/N ratio, low distortion, uniform frequency response
and optimal sound quality maintained at any volume setting.

■

Attenuator and balance control also implemented by AAVA,
eliminating additional circuitry.

■High-resolution volume control: Combination of V-I con-

verter amplifiers gives 65,536 possible volume steps.

The amplification circuitry of C-3850 consists of a total of 18 unit amplifiers,
including I-V assembly, AAVA circuitry, balanced input and balanced
output amplifiers.

Turning the volume knob on the front
panel causes the actual volume level
position to be detected. The corre­sponding signal is se nt to a CPU
which in turn contr ols the current
switches and thereby the gain of the
AAVA ci rcuitry. The massive knob
extruded from a solid aluminum block
and mounted on large-diameter shaft
has exactly the rig ht amount of
inertia. Together with the low-friction
internal mechanism this provides a
silky smooth operation feel and also
allows extremely quiet motor-driven
operation.

The Essence of Technology

The Beauty of Tradition

Precision Stereo Preamplifier

As the ultimate analog preamplifier, the C-3850 has been
honed to perfection, bringing together sophisticated
technology and carefully selected materials in a package of
refined visual appeal. The gold-hue front panel and the
exquisite wood cabinet reflect true craftsmanship, as the
natural wood grain of each individual unit has been
mirror-finished by expert hands. The result is a product that
exudes a graceful and dignified atmosphere.

Features and Functions

■Ideal power supply design realizes dual mono construction with newly

developed high-efficiency toroidal transformers and filtering capacitors
(10,000 µF x 12) selected for sound quality.

■Logic-controlled relays for signal switching assure high sound quality and

long-term reliability.

■Versatile arrangement of line and balanced input and output connectors.

■Printed circuit boards for signal transmission are made from glass cloth

fluorocarbon resin with low dielectric constant and minimum loss.

■Selectable preamplifier gain with three settings (12 dB, 18 dB, 24 dB).

■EXT PRE function allows use of external preamplifier.

■Output phase selectable individually for each input, with visual indication.

When INV LED is lit, output phase is inverted. When LED is out, phase is
normal.

■Dedicated headphone amplifier with three selectable gain settings.

■Advanced High Carbon cast iron insulator feet with superior damping

characteristics further enhance sound quality.

■Massive wood cabinet with natural grain finish.

■More versatile features:

● 

Provisions for recording and playback with a recorder.

●

Attenuator (-20 dB).

●

Loudness compensator with three selectable characteristics

enhances low end presence.

●

Alphanumeric indication of input position.

●

Large, easy to read numeric indication of volume level

setting.

■Unit amplifier assembly

A total of 18 unit amplifiers handle the signal
transmission for the left and right channel.
The printed circuit boards are made from
glass cloth fluorocarbon resin, and the
copper foil surfaces are gold-plated. The unit
amplifiers are mounted on a glass epoxy
motherboard, and left and right sections are
kept completely separate. An 8 mm thick
frame made of hard aluminum prevents
mutual interference by providing electrical
shielding and suppressing physical vibra­tions.

■Supplied remote commander RC-210

Allowsvolumeadjust ment ,in put
sourceswitching,an d
otheroperations.

High-ef ficienc y toroi dal pow er tran sformer s

Assembl ywith linel evelan dbalan ced

inputa ndoutp utcon nectors

Phase selector button

Gain selector

EXT PRE phase setting indication

EXT PRE select or

Audio q uality filter ing cap acitors

Parts s elected for h igh sou nd qual ity an d relia bility

Headpho ne

level s elector

Ultra h igh per forman ce

operati onal am plifie rs

LEFT

CHANNEL

LEFT
CHANNEL
INPUTS

RIGHT

CHANNEL

qInpu t selec tor

wInpu t displ ay

LINE(AD)

TUNER

CD

LINE 1

LINE 2

LINE 3

BAL(AD)

CD-BAL

BAL 1

BAL 2

REC

RECORDER

PLAY

rGain select or

eFunction indicators

OUTPUT PHASE
MONO

RECORDER

12 dB 18 dB 24 dB

INPUT

SELECTOR

PLAY

PHASE

MONO

tLoud ness co mpen sator s elec tor

OFF 1 2 3

yFunc tion indica tors

RECORDER
COMPENSATOR
ATTENUATOR

Block Diagram

(BalancedAccuphase Analog Vari-gain Amplifier)

Balanced AAVA

+

–

Volume
Balance

CPU

Attenuator

–

+

Same as LEFT CHANNEL

uVolu me l evel di spla y

iVolume control

knob

+

–

FEEDBACK

COMP 1,2,3

FEEDBACK

–

+

@0Recorder playback/

recording connectors

!9Line input connectors

LINE(AD)TUNER CD 
LINE 1, 2, 3

COMP

COMP

HP GAIN

+

–

–

+

LINE AMPLIFIER

FEEDBACK

–

+

FEEDBACK

–

+

+

–

FEEDBACK

BALANCED
AMPLIFIER

FEEDBACK

–

+

HEADPHONE

AMPLIFIER

Rear PanelFront Panel

@1 Line output

connectors(2 sets)

EXT PRE

OUTPUT

EXT PRE

OUTPUT

EXT PRE

OUTPUT

OUTPUT

From RIGHT CHANNEL

@2Balanced output connectors (2 sets)

With line input signal: pin ② negative (-), pin ③ positive (+)
With balanced input signal: same phase as source equipment
[Can be switched with output phase selector button

LINE 1

LINE 2

BAL 1

BAL 2

LINE

BAL

HEADPHONE
OUTPUT

LEFT
CHANNEL
OUTPUTS

LEFT
CHANNEL
EXT PRE
INPUTS

!2

]

oPower switch !8Attenuator button

!0Output selector

EXT PRE ALL  
BAL LINE OFF

!1Display

ON/OFF button

!2 Output phase

selector button

!3Stereo/mono

selector button

Sub panel

!7Headphone jack

Pressing this button
opens the sub panel

!6Headphone level selector

  LOW MID HIGH

!5Recorder output ON/OFF and PLAY buttons

!4Balance control

@3Balanced input connectors (4 sets)

BAL(AD)CD-BAL BAL 1,2

C-3850 Guaranteed Specifications ＊Guaranteed specifications are measured according to EIA standard RS-490. ＊Gain selector set to 18 dB position

● Frequency  BALANCED/LINE INPUT
Response  3

 20

−

200,000 Hz ＋0 −3.0 dB

−

20,000 Hz ＋0 −0.2 dB

● Total Harmonic Distortion (for all inputs) 0.005%

● Input Sensitivity, Input Impedance

Input

BALANCED

LINE

● Rated Output Voltage, Output Impedance

BALANCED/LINE OUTPUT 2 V 50 ohms

● S/N Ratio

● Maximum Output Level (0.005% THD, 20

BALANCED/LINE OUTPUT: 7.0 V
RECORDER REC(with AD input): 6.0 V

● Maximum Input

Level

LINE INPUT: 6.0 V

● Minimum Load Impedance

BALANCED/LINE OUTPUT: 600 ohms

RECORDER REC: 10 kilohms

Remarks

This produc t is available in ver sions for 120/ 220/ 230 V AC. Make sur e that the voltag e shown on the rear panel

★

matches the AC line voltage in your area.

The 230 V versi on has an Eco Mode tha t 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.

★

Input

BALANCED

LINE

BALANCED INPUT: 6.0 V

Sensitivity

252 mV
252 mV

For 0.5 V output

115 dB
115 dB

−

20,000 Hz)

63 mV
63 mV

40 kΩ(20 kΩ/20 kΩ)

For rated output

Input shorted, IHF-A weighting

S/N ratio at rated output

Input impedance

20 kΩ

S/N ratio (EIA)

110 dB
110 dB

●Crosstalk

● Gain (Gain selector: 18 dB)＊Gain selector allows increase or decrease by 6 dB,

 BALANCED INPUT → BALANCED OUTPUT: 18 dB
BALANCED INPUT → LINE OUTPUT: 18 dB
LINE INPUT → BALANCED OUTPUT: 18 dB
LINE INPUT → LINE OUTPUT: 18 dB
BALANCED/LINE INPUT → RECORDER REC: 0 dB

● Loudness Compensation

 1:

● Headphone Jack

Output Level: 2 V (40 ohms)
Gain (LOW, MID, HIGH): ±10 dB from standard MID level

● Attenuator

● Power Requirements

●

Power Consumption

● Maximum Dimensions

 Width 477 mm (18-3/4”)
Height 156 mm (6-1/8”)
Depth 412 mm (16-1/48”)

● Mass 25.0 kg (55.1 lbs) net

32.0 kg (70.6 lbs) in shipping carton

@4EXT PRE input connectors (2 sets) LINE/BAL

@5AC power supply connector



−

90 dB or better at10 kHz (EIA)

except for REC output.

＋

2 dB(100 Hz), 2: ＋4 dB(100 Hz), 3: ＋6.5 dB (100 Hz)



Suitable impedance: 8 ohms or above

−

20 dB

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

55 watts

Supplied accessories: AC power cord

Audio cables with plugs ASL-10
Remote commander RC-210
Cleaning cloth

★

●

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

5年間保証

F1505Y PRINTED IN JAPAN 850-2192-00（B1）