Accuphase PX-650 Brochure

m Digital power amplifier with totally separate six-channel configuration m Output power 200 watts × 6 into 4 ohms, 150 watts × 6 into 8 ohms m Bridged operation further increases output to 450 watts × 3 into 6 ohms

and 420 watts × 3 into 8 ohms m Instrumentation amplifier principle for fully balanced signal paths m Large 820 VA toroidal transformer m Balanced inputs m Three large analog power meters m Large-size speaker terminals

The PX-650 represents a successful blend of digital audio technology with Accuphase's rich expertise in the field of analog power amplifiers. The result is a six-channel digital power amplifier ideally suited for high-end home theater systems. Because six identical high-efficiency power units operating in digital mode are used, all channels provide the same excellent sound quality. The PX-650 can drive any kind of speaker with ease and authority, creating a spacious surround sound stage with pinpoint imaging and impressive dynamics. Thanks to its high efficiency, the digital circuitry keeps thermal energy generation low, making it possible to reconcile high output power levels with compact unit dimensions. This is especially welcome in multi-channel systems for home theater applications. The capability for high power and small size has been a recognized advantage of the digital principle for power amplifiers, but performance and sound quality related problems had to be overcome before adoption in a high-end audio product was possible. The PX-650 represents a breakthrough in the field. It is the result of a highly focused step-by-step approach to identify and solve these pertinent problems. Circuit topology as well as the selection of components and materials are based on extensive listening tests. The aim was nothing less than to realize pure audio quality of the highest standard while making best use of the digital approach. In performance as well as in sound quality, the PX-650 is a case in point. The digital switching principle boasts extremely low internal losses. The power supply is not called upon to provide superfluous energy, which in turn keeps power consumption and therefore operation temperatures low. A power supply rated for the same capacity in an analog amplifier would be much less powerful. The knowhow accumulated by Accuphase in the analog field is also in evidence in the PX-650, as exemplified by its large toroidal transformer. By combining the advantages of the digital principle, namely high power and low current consumption, with solid engineering and sophisticated design expertise, Accuphase has opened up a new chapter in digital audio.

Balanced signal transmission with instrumentation amp configuration

The PX-650 features the highly advanced "instrumentation amplifier" principle whereby all signal paths from the inputs to the power amp stage are fully balanced. Ideal signal transmission conditions result in excellent CMRR (common mode rejection ratio) and minimal distortion. Another significant advantage is that external noise and other external influences are virtually shut out. The result is a drastic improvement in operation stability and reliability.

Signal input stage Power amp stage

GAIN CONTROL

CIRCUIT

–

NFB

NETWORK

NFB

NETWORK

–

DIGITAL POWER

AMP.

OUTPUT

INPUT

–

INPUT

Instrumentation amplifier configuration (1 channel)

Six-channel digital power amplifier – Six totally separate power units with identical performance. Discrete delta-sigma type digital power units ensure extremely low noise. Large 820 VA toroidal transformer and large filtering capacitors provide ample muscle: 200 watts × 6 into 4 ohms or 150 watts × 6 into 8 ohms. Bridged mode allows upgrade to 3-channel amplifier with 420 watts × 3 into 8 ohms.

n Six digital power amp units with identical performance allow

configuring a superb 5.1 channel surround system using a single component

With all six channels operating, the PX-650 delivers 200 watts × 6 into 4 ohms and 150 watts × 6 into 8 ohms. In 2-channel mode, the unit becomes even more powerful, with 250 watts × 2 into 4 ohms and 170 watts × 2 into 8 ohms.

n Bridged operation allows upgrade to a high-output 3-channel

amplifier

The two channels in all three blocks can be run in bridged mode, resulting in a full 450 watts × 3 into 6 ohms and 420 watts × 3 into 8 ohms. This represents top performance with power to spare.

n Power supply features large toroidal transformer and

ample filtering

The toroidal power transformer of the PX-650 is rated for 820 VA, and filtering is provided by two aluminum electrolytic capacitors with ample 33,000 µF rating.

n Gain selector provides 6 dB increase in normal or

bridged operation

n Mode selector allows easy implementation of

bridged operation

n Balanced inputs highly resistant to externally

induced noise

n Three analog power meters with direct reading scale

A meter selector button allows use of the meters for all six channels. On/off switching for meter operation and illumination is also provided.

n Front-panel input selector button allows easy choice

of balanced and unbalanced inputs

n Large-size speaker terminals compatible with

Y lugs and banana plugs

AMP.

BALANCED INPUT

LEFT

UNBALANCED INPUT

BALANCED INPUT

UNBALANCED INPUT

BALANCED INPUT

UNBALANCED INPUT

INPUTS

BALANCED INPUT

UNBALANCED INPUT

BALANCED INPUT

RIGHT

UNBALANCED INPUT

BALANCED INPUT

UNBALANCED INPUT

PX-650 Block Diagram

INPUT SELECTOR

MODE SELECTOR

–

GAIN CONTROL

–

AMP.

–

GAIN CONTROL

–

AMP.

–

GAIN CONTROL

–

AMP.

–

GAIN CONTROL

–

AMP.

–

GAIN CONTROL

–

AMP.

–

GAIN CONTROL

–

AMP.

METER CIRCUIT

NFB

Large toroidal power transformer

Meter selector buttons

Input selector buttons

DIGITAL POWER AMP.

Power amplifier unit (2 channels)

Large filtering capacitors

Balanced/unbalanced input connectors

Large-size speaker terminals

MUTING

BRIDGE LEFT.A

BRIDGE C.D

BRIDGE RIGHT.B

RELAY

MUTING RELAY

LEFT

OUTPUT

SPEAKERS

OUTPUT

RIGHT

OUTPUT

PROTECTION CIRCUIT

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