● Revolutionary AAVA volume control ● Power MOS-FETs in triple
parallel push-pull configuration driven in pure class A ● Current feedback
principle and MCS+ topology in power amplifier section ● Logic-control
relays for straight and short signal paths ● Sturdy power supply withlarge toroidal transformer and high filtering capacity ● EXT PRE button
allows independent use of preamplifier and power amplifier sections

The ultimate integrated pure class A amplifier – Power MOS-FETs arrangedin triple parallel push-pull configuration. Innovative AAVA volume control.
Strong power supply with large toroidal transformer and high filtering capacity
supports linear output progression of 120 watts/ch into 2 ohms, 60 watts/chinto 4 ohms, or 30 watts/ch into 8 ohms. Power amp section uses current feedbackfor optimum high-frequency phase characteristics and MCS+ topology.
considerable amount of space. In order to enable
the use of AAVA in an integrated amplifier,advanced design know-how and mounting
technology were brought into play, to increase
component density while keeping sonic purity andperformance at the high level that is the hallmark
of Accuphase. The result speaks for itself.
The power amplifier section features the highly
acclaimed current feedback principle developedby Accuphase, as well as further improved “MCS+”
circuit topology, for even better electricalcharacteristics. The output stage devices are

The first integrated pure class A amplifier fromAccuphase, the E-530, drew a lot of attention andpraise. The E-550 now takes over as a further
improved and fully redesigned successor model.
It stands at the pinnacle of integrated amplifiers,featuring latest technology and strictly selectedhigh-quality parts. For the first time in an integrated
amplifier, it offers the revolutionary AAVA typevolume control. In AAVA, amplification and volumecontrol are fully unified, and no variable resistors
are used. This ensures excellent sound quality andperfor mance, but the circuitry requires a

power MOS-FETs famous for their musicalqualities, arranged in a triple parallel push-pull
configuration and driven in pure class A. Low
output impedance and constant voltage drive
ensure superb speaker control. The large highefficiency toroidal transformer (430 VA) in thepower supply, along with eight 10,000 µF filtering
capacitors selected for their sonic properties
support linear progression of output regardless ofimpedance, with a per-channel rating of 120 watts
into 2 ohms, 60 watts into 4 ohms, or 30 watts into
8 ohms.

AAVA (Accuphase Analog Vari-gain Amplifier) volume control■ Volume control resolution
AAVA adjusts the listening volume by means of 16 current switches which areoperated by 16 weighted V-I converter amplifiers. The number of possible volume
steps set by the combination of these converter amplifiers is 2 to the power of
16 = 65,536.
■ AAVA maintains high S/N ratio and uniform frequency response
With conventional volume controls, the impedance increases significantly atsettings that correspond to normal listening levels, thereby leading to increased
noise. Because AAVA performs adjustment by selective use of V-I converter
amplifiers (changing the actual gain), there is no change in impedance andthus no deterioration of S/N ratio or alteration of frequency response. Changing
the volume with AAVA does not mean introducing noise or detracting from thehigh performance of the amplifier.
■ Same operation feel as a conventional high-quality volume control
The volume control knob position is detected by a dedicated CPU which inturn selects the current switches for AAVA operation. Operating the knob
therefore feels exactly the same as with a conventional control, and as before,
operation via the remote commander is also possible.

■ Simple circuit configuration
AAVA unifies the amplifier and volume control functions, resulting in a circuitthat is electrically very simple. Long-term reliability is excellent, with performanceand sound quality that will remain unchanged also after prolonged use.
■ AAVA means analog processing
The AAVA circuit converts the music signal from a voltage into a current,switches gain by means of current switches, and then reconverts the current
into a voltage. The entire process is carried out in the analog domain.
■ No more left/right tracking differences or crosstalk
Because AAVA is an electronic circuit employing highly precise metal film
resistors, there is virtually no left/right tracking error also at low volume levels.
Since channels can be kept separate, crosstalk also does not present a problem.
■ Attenuator and balance control also implemented by AAVA
The functions of the attenuator and the left/right balance control are coveredby the AAVA circuit as well, eliminating the need for additional circuit stages.
Keeping the configuration simple helps to maintain high performance and sonicpurity.

16 current switches(65,536 possible combinations)

I -V Converter

The newly developed volume control called AAVA (Accuphase Analog
Vari-gain Amplifier) is totally different from conventional controls using
resistors. Because the music signal does not pass through variable
resistors, it is not affected by changes in impedance. This means thathigh signal-to-noise ratio and low distortion of the signal are maintained.
Adjusting the volume does not introduce any deterioration in sound quality.

Reconversion ofcurrent into voltage

BUFFEROUTPUT

INPUTCurrent values
are added

Input musicsignalCPU

VolumeBalance
Attenuator

V- I Converter
Conversion into current with 16
weighting stages (1/2 - 1/216)

CPU detects position of volume
knob and operates current on/off
switches according to knob position

Volume knob is turnedand position is detected

AAVA operation
AAVA operates by feeding the music signal to a V-I (voltage - current) converting amplifier
where it is weighted in 16 steps [1/2, 1/22, ... 1/215, 1/216]. The 16 current steps are turnedon or off by 16 current switches, and the combination of switch settings determines theoverall volume. The switching operation is controlled by a CPU according to the position of
the volume control knob. The combined signal current forms a variable gain circuit that
adjusts the volume. Finally, the combined current is converted back into a voltage by an
I-V (current - voltage) converter.

■ AAVA control assembly withthree AAVA units and CPU
arranged neatly on a motherboard■ Output
amplifie
triple ppower M
mountesink

■ Supplied remote commander RC-200
Allows volume adjustment and input
source switching■ The output stage uses power
MOS-FETs in a triple parallelpush-pull configuration driven
in pure class A. Output power
progression is linear, with aper-channel rating of 120 watts
into 2 ohms, 60 watts into 4ohms, or 30 watts into 8 ohms.

■ Output stage and power
amplifier assembly withtriple parallel push-pullpower MOS-FET devices
mounted to large heatsink

Power MOS-FET devices■ Power amplifier section uses MCS+ topology and current feedback principle to achieve
excellent sound quality and optimum high-frequency phase characteristics.
■ Logic-controlled relays assure highsound quality and long-termreliability.
■ Balanced input connectors shut out
external noise interference.
■ “High Carbon” cast iron insulator feetwith superior damping characteristics fur ther enhance soundquality.
Gold-plated input/output jacks connected directly to relays■ Ample power supply withlarge high-efficiency
toroidal transformer (430VA) and 10,000 µF × 8filtering capacitors

BIAS
STABILIZER+ B3+ B1

REGULATOR

Q1Q5

Q9

Q 13

Q7

Q 11

Q 15+ B2Q 17
Q3Q 19Q 21

Q 23

Q 25peakp ow e r■ Option board slots allow
functional expansion.

BIAS
STABILIZERNFBNETWORKINPUT
Biasstabilizer

OUTPUTBIAS
STABILIZER

Q2
Q6

Q 10

Q 14

Q8

Q 12

Q 16

Q 18

Q 20

Q 22

Q 24

Q 26

- B2Q4■ Analogmeters

REGULATOR- B3BIASSTABILIZERMCS+ (Multiple Circuit Summing-up)- B1

Toroidal transformer

Filtering capacitors■ Two sets of large-size speaker terminals accept either Y lugs or banana plugs.
■ E-550 front panel switchingenables MC/MM selection
for Analog Disc Input Board
AD-20.
■ EXT PRE button andpreamplifier output/power
amplifier input connectors
allow independent use ofpreamplifier and power
amplifier sections.
Large-size speaker terminals

■ Tone controls using summing active filters for
optimum sound quality-A1-A2

InputOutputOption Boards
Digital Input Board

Three types of option boards can be used in the E-550: theDigital Input Board DAC-20, Analog Disc Input BoardAD-20, and Line Input Board LINE-10. These boards can beinstalled in the rear-panel slots as required.
● It is possible to install two identical boards.

F1● Inputs for coaxial and optical fiber connections areprovided.

● The Digital Input Board DAC-10, Analog Disc Input Board AD-9/
AD-10, and Line Input Board LINE-9 can also be used.

VR1● When using the AD-9/AD-10, the MC/MM button of theE-550 has no effect. MC/MM switching must be performed on theboard.

F2DAC-20

The board features an MDS (Multiple Delta Sigma) ++ type
D/A converter and allows direct digital connection of a CDplayer, MD or DAT recorder or other component with digitaloutput (sampling frequency up to 96 kHz, 24-bit), for highquality music reproduction.

Analog Disc Input Board

AD-20

This board serves for playback of analog records. Itcontains a high-performance, high-gain phono equalizer.

VR2Tone control circuit principle● MC/MM switching is possible on the front panel of the E-550.
● Internal DIP switches control MC input impedance andsubsonic filter on/off.

■ Loudness compensator for enhanced bass at low
listening levels
18MC

1614

Gain:
62 dB
Input impedance: 10/30/100 ohms
(selectable)

12
LOUDNESS COMPENSATOR: ON10MM

Response in dB

86

Gain:
36 dB
Input impedance: 47 kilohms

420

Line Input Board-2

LINE-10-4

This option board provides an additional set of unbalanced
line inputs.

-6
10100

1k
Frequency in Hz

10k

100k

AD-20

Compensator characteristics

Option board installation example■ Front panel

GUARANTEED SPECIFICATIONS[Guaranteed specifications are measured according to EIA standard RS-490.]● Continuous Average Output Power (both channels driven, 20 ~ 20,000 Hz)
150 watts per channel into
1 ohm (✽)
120 watts per channel into
2 ohms
60 watts per channel into
4 ohms
40 watts per channel into
6 ohms
30 watts per channel into
8 ohmsNote: Ratings marked ✽ are for music signals only.
● Total Harmonic Distortion (both channels driven, 20~20,000 Hz)
0.05% with
2-ohm load
0.02% with4 to 16-ohm load
● Intermodulation Distortion

0.01%● Frequency Response
HIGH LEVEL INPUT/POWER INPUT
For rated continuous average output: 20 ~ 20,000 Hz +0,–0.2 dB
For 1 watt output:
2 ~ 150,000 Hz +0,–3.0 dB● Damping Factor

Pressing thisbutton opens
the sub panel.

■ Rear panel
Option board
installation slots

140 (with 8-ohm load, 50 Hz)● Input Sensitivity, Input Impedance
Input
HIGH LEVEL INPUTBALANCED INPUTPOWER INPUT

Sensitivity
For rated output
For 1 W output (EIA)
77.7 mV
14.2 mV
77.7 mV
14.2 mV
0.617 V113 mV

Input
impedance
20 kΩ40 kΩ20 kΩ● Output Voltage, Output Impedance PRE OUTPUT:
0.617 V, 50 ohms
(at rated continuous average output)★

A Input selector
J Bass control
LINE 2 LINE 1 LINE-BAL CD-BAL CD
K Treble control
TUNER OPTION 1 OPTION 2
L Balance control
B Left/right channel output meters
M Attenuator button
C Function indicator LEDs
N Headphone jack
D Volume control
O Line inputs (unbalanced)
E Power switch
P Tape recorder inputs and outputs
F Speaker selector OFF A B A+B
Q Left/right speaker output terminals A/B
G Copy selector1➞2 OFF2➞1R CD/LINE inputs (balanced)
H Recording output selector REC OFF, SOURCE, 1, 2
S Preamplifier outputs
I Function buttons
21 T Power amplifier inputs
MC/MM, EXT PRE, MONO/STEREO, Meter ON/OFF U
21 AC inlet ★
Compensator, Tone control ON/OFFRemarks★ This product is available in versions for 120/230 V AC. Make sure that the voltage shown on therear 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 anddestination country.

■ Supplied accessories:● GainHIGH LEVEL INPUT ➞POWER INPUT➞● Tone Controls

Turnover frequency and adjustment range
BASS:
300 Hz ±10 dB(50 Hz)
TREBLE: 3 kHz ±10 dB (20 kHz)● Loudness Compensation+6 dB (100 Hz)● Attenuator–20 dBPRE OUTPUT: 18 dB
OUTPUT:
28 dB● Signal-to-Noise Ratio
Input shorted (A weighting)
S/N ratio at rated output

EIA S/N

HIGH LEVEL INPUTBALANCED INPUTPOWER INPUT

98 dB
92 dB
120 dB103 dB103 dB117 dB● Power Level Meters

Logarithmic compression, peak reading meters
Output dB/% scale● Load Impedance

2 ~ 16 ohms

Input

● Stereo Headphones

Suitable impedance:● Power Requirements

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

200 watts idle, 300 watts in accordance with IEC-60065● Maximum Dimensions

Width
HeightDepth● Mass23.9 kg (52.7 lbs) net
30.0 kg (66.1 lbs) in shipping carton

8 ~ 100 ohms

465 mm (18-5/16”)
196 mm (7-11/16”)
427 mm (16-13/16”)● Supplied Remote Commander RC-200
Remote control principle:
Infrared pulse
Power supply:
3 V DC (IEC R03 batteries x 2)
Maximum dimensions:
56 mm × 75 mm × 26 mm
Mass:
153 g (including batteries)• AC power cord
• Remote Commander RC-200• Specifications and design subject to change without notice for improvements.

http://www.accuphase.com/

K0505YPRINTED IN JAPAN 851-0152-00 (AD1)