Accuphase E-407 Handmatig - Pagina 2

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The E-407 represents a new pinnacle of ampli-

fier design. Featuring latest technology and us-

ing only the highest quality materials, this inte-

grated stereo amplifier is destined to become a

new reference. Frequency response, S/N ratio,

and all other performance aspects make the

E-407 perfectly suited for the new generation

of ultra high quality program sources such as

SACD and DVD-Audio.

An integrated amplifier provides various advan-

tages such as convenient operation and modest

space requirements. However, because its over-

all gain is very high, even the slightest interfer-

ence or crosstalk at the input can have a consid-

erable effect on the sonic result. To preclude this

possibility, the E-407 is designed to achieve total

electrical and structural separation of the

preamplifier and power amplifier sections. These

two parts operate as if they were entirely sepa-

rate components. A switch even allows using the

preamplifier and power amplifier independently.

Accuphase's highly acclaimed current feedback

topology virtually eliminates phase shifts in the

upper frequency range and assures outstanding

performance and sound quality. The power am-

plifier output stage employs a triple parallel push-

pull configuration, using multi-emitter power tran-

sistors designed for high-power audio applica-

tions. Ample muscle is provided by the power

supply section which features a massive, highly

efficient toroidal power transformer housed in a

diecast enclosure equipped with heat fins.

In the standard configuration, the E-407 has six

inputs, two of which employ the balanced princi-

ple that assures ideal signal transmission char-

acteristics. Provisions for two tape recorders, with

easy dubbing in both directions, tone controls, and

loudness compensation are further attractive fea-

tures. An optional analog disc input board allows

reproduction of analog records with outstanding

sonic quality.

The external design of the E-407 continues the

Accuphase tradition, featuring a champagne gold

brushed front panel. Two large power meters in

the center are flanked by the input selector sec-

tion and the volume control. Not only by virtue of

Figure 1 Circuit diagram of power amplifier section (one channel)

State-of-the-art integrated amplifier features current feedback topology

for superb high-range phase fidelity. Wide-range power transistors in

triple parallel push-pull configuration and massive toroidal transformer

deliver ample power: 260 watts × 2 into 4 ohms, 180 watts × 2 into 8

ohms. Option board enables analog record reproduction in top-notch

quality.

its excellent sound, from its looks as well the

E-407 is a great addition to any living room.

Triple parallel push-pull output stage delivers

quality power: 260 watts/channel into 4 ohms,

220 watts/channel into 6 ohms or 180 watts/

channel into 8 ohms

The output devices are multi-emitter power tran-

sistors designed for high-power audio applica-

tions. These devices have excellent frequency re-

sponse, forward-current transfer ratio linearity, and

switching performance characteristics. They are

connected in a triple parallel configuration (Fig-

ure 1) for low impedance and mounted directly

on a large heat

sink to assure ef-

ficient dissipation

of thermal energy.

This allows the E-

407 to deliver am-

ple power output,

amounting to 260

watts into 4 ohms,

220 watts into 6 ohms, or 180 watts into 8 ohms

per channel.

Current feedback topology in power amplifier

and preamplifier sections guarantees top-

level performance

In the E-407, the signal current rather than the

voltage is used for feedback. Figure 2 shows the

operating principle of this circuit. At the sensing

point of the feedback loop, the impedance is kept

low and current detection is performed. An im-

pedance-converting amplifier then converts the

current into a voltage to be used as the feedback

signal. Since the impedance at the current feed-

Figure 2 Principle of current feedback amplifier

Bias

stabilizer

back point (current adder in Figure 2) is very low,

there is almost no phase shift. Phase compensa-

tion can be kept to a minimum, resulting in excel-

lent transient

response and

superb sonic

transparency.

Figure 3 shows

frequency re-

sponse for dif-

ferent gain set-

tings of the cur-

rent feedback

amplifier. The graphs demonstrate that response

remains uniform over a wide range.

Discrete-type line amplifier for superior sonic

purity

The line amplifier is entirely built from discrete

parts, to assure optimum performance. Using a

principle developed by Accuphase, a differential

pure complementary push-pull circuit is combined

High-current power transistors

with a single-ended push-pull emitter follower

output stage. This comparatively simple topology

reduces the need for phase compensation, re-

sulting in effortless, utterly natural and transpar-

ent sound.

Highly reliable logic-controlled relays

Program source switching is performed by logic-

controlled relays which are arranged so as to

permit

shortest possi-

ble

paths.

her metically

sealed relays

are high-qual-

ity types devel-

oped specifi-

cally for de-

manding com-

munication ap-

plications. The contacts are twin crossbar types

plated with gold for minimum contact resistance

and outstanding long-term reliability.

Tone controls use summing active filters for

pure sound

The tone control circuitry in the E-407 was spe-

cially designed with summing active filters. Fig-

ure 4 illustrates the operation principle of this cir-

Figure 3 Frequency response with current feedback

(Response remains uniform also when gain changes)

Line amplifier assembly with

current feedback circuitry

the

signal

The

Relays connected directly to

gold-plated input/output jacks