Accuphase E 305 Brochure

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Accuphase E 305 Brochure

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o Singlechip dual NPN transistor
95ingte-chlp dual FET

o Single—chip dual PNP transistor
0 Servo l0

0 Filter capacitors tor drive stage power supply
0 Class A transistor preoriver

o N-ch power MOS FET driver
0 NPN output transistors

o PNP output transistors

0 P—ch power MOS FET driver
0 Class A transistor predrlver

Q Servo l6

0 Dual FET input cascode bootstrap circuit amplifier (left channel)

O Output booster (tett channel)
9 Current mirror circuits (left channel)

@Triple parallel dilierential super low noise FETs (6 devices) (lett channel)

0 Gain switching relay
® Input impedance switching relay
0 Servo IC

Q Triple parallel diiierential super low noise FETs (6 devices) (right channel)

0 Current mirror circuits (right channel)
0 Low-noise regulated power supply
w Output booster (right channel)

9 Dual FET input cascade bootstrap circuit amplifier (right channel)

An integrated amplilier. as the name implies, com»
bines all amplilying stages into a single chassis.
This makes lor easy operation, but it also makes it
very dillicult to achieve impeccable sound quality.
The main reason lor this predicament is that the
total gain oi such a unit exceeds 100 dB. which
easily gives rise to mutual interlerence between the
various stages.

Accuphase linally provrdes a solution which tullills
even the most severe audiophile demands. Draw-
ing on our long experience in building separate
type ampliliers of world renown. we have used only
the linest materials and applied innovative design
to create the E305. lt realizes the ultimate goal: to
provide the quality of a standalone preamplilier
and power ampliliei in an integrated package.
The E7305 consists of a phone equalizer stage tor
reproduction ol analog discs, a high-gain pream-
plilier. and a power amplilier. Each oi these three
units is optimized tor the ultimate in performance.
lnterterence between stages is eltectively pre—
vented by using separate power translormer Windr
ings lor the phono and preamplilier stage and the
power amplilier. The preamplifier employs sophisti
cated voltage regulator circuitry tor utterly stable
operation Ingenious Circuit design and parts layout
combined with etlective shielding turther prevent
the possibility of static or magnetic interlerence,
The power amplilier draws on a highly capable
power supply and employs a triple parallel pushr
pull design in the output stage. It delivers 130 watts
per channel into 8 ohms and 180 watts per channel
into 4 ohms. It can even drive 2-ohm loads with 250
watts of power per channel This capability is desir-
able not only when using speakers wrth very low
impedance ratings. Also with normal speakers. the

A Power amplifier unlt (single channel)
v Preamplifier section PCB

' you...

complexities oi the musical signal can be conveyed
more iaithlully by an amplilier with superior lowr
Impedance drive capacity.

For optimum llexibility. the E-305 provrdes a total Ol
10 inputs. so that it can ellectively control the entire
system Two Inputs are balanced types. ollering
ideal transmission characteristics. Versatile tape
recorder lacrlities are another highlight oi this am
plilier. A FlEC selector lets you choose any source
tor recording independent ot the program repror
duced over the speakers. and a TAPE COPY switch
provides the capability lor hassle-tree tape dub-
bing Tone controls and a loudness compensator
circuit let you improve the tonal qualities ol source
material ii required. As the tone controls empioythe
summing active lilter principle. they have no detrir
mental etiect on sound quality,

The design ol the E7305 combines ease ol opera-
tion With high Visual appeal Large power meters
are arranged in the center oi the front panel. tlanked
by the input selector to the tell and a large volume
control knob to the right Switches tor less frequent-
ly used lunctions are arranged behind a hinged
panel, giving the amplilier an uncluttered appear-
ance not unlike a power amplilier The E-305 looks
every bit as good as it sounds.

Poweflul mullet push-pull output
stage rollobty drivel law-Impedance
loads and deliver: 130 watts per
1 channel Into 3 ohms and 350 watts per
channel into 2 ohms.
Fig 1 shows the circuit design ot the E7305. The
output stage employs three pairs of bipolar transis—
tors (0‘7 7 022) in a parallel push-pull configuration.
Each transistor has a maximum heat dissipation

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Fla. 1 Power amplifier at 5-305

(Pc) rating ot 130 watts. resulting in a combined
maximum heat diSSipation of 780 walls This genera
ous design is very elleclive to drive low-impedance
loads wrth ample power. but it also contributes to
improved linearity when using speakers with '-
mal impedance characteristics. The E-BOS devs
130 watts per channel into 8 ohms. lBO watts into 4
ohms. and a lull 250 walls at high-quality power into
2 ohms

Power drive any. wlth tho quality of

”parole-typo amplifiers
As can be seen lrom Fig. 1. the predriver circuit for
the output stage employs MOS FET devices which
are ideal torthis purpose. Theyprowdetherequired
low output impedance and high drive voltage. re
sulting in operation equivalent to non-switching
class A drive.
The input stage consists oi the cascode connected
devices Ora and Oz. and Q“, and 03. Together with
the constant-current load 04 and 05. this ensures
wide bandWidth and high linearity The ditierential
amplitier in the subsequent stage uses a coma
plementary circwt with singleechip dual transistors.
Low noise and extremely stable operation are the
main advantages oi this approach.
In every aspect. the power ampliiier section oi the
E7305 rivals the performance oi a separatetype
amplitier,

Completely direct-coupled Dc servo
design from phono input all the way to
the outputs
All unit amplitiers. from the phono input for analog
discs up to the output stage. are linked directly.
without any coupling capacitors in the signal path.