Accuphase P 102 Brochure

Page 1

BALANCED CLASS-A STEREO POWER AMPLIFIER

P-102

O Class-A parallel push-pull output stage
0 Low-impedance load drive capability
0 Full twin mono construction

alanced input circuits

Page 2

The Accuphase power amplifier P-102 isthe ideal performer forthe age of high-
quality program sources.

It employs a fully balanced circuit configuration throughout, with two bridged
pushApull power amplifiers foreach channel, resulting in an impressive total 0M
amplifiers within one enclosure.

The balanced signal transmission used in the P-102 offers a perfect solution
which ensures that the voltage potential in the ground line is zero at all times.
This effectively prevents any kind of external interference. The output devices
of the amplifier operate always in the linear range, thanks to the class-A drive
principle. Crossover distortion is completely eliminated, and the current
supply is always kept constant, which has the same effect as using a power
supply with infinite capacity. Construction of the amplifier is totally mono-
phonic, with separate power transformers for the left and right channels.
The design of the P-102 stands in the same tradition as the top-of-the-Iine P-
500, with large, wide level meters behind a thick glass panel and all controls
and functions arranged behind a subpanel, This gives the amplifier an appear-

By using the P-102 in combination with the preamplifier 0-202, an entire
system with fully balanced signal transmission can be created, which offers the
ultimate in reproduction quality. The sound quality potential of truly accurate
program sources can now be fully appreciated in the home, for unlimited
musical enioyment.

ance of beautiful and uncluttered elegance.

FULLY BALANCED POWER AMPLIFIER
WITH TWO ALL-STAGE PUSH-PULL POWER
UNITS IN BRIDGED CONFIGURATION

For the transmission of Signals in an audio sys-
tem, two basic patterns are available: the unbal-
anced principle as shown in Fig. l-(a) and the
balanced principle of Fig. l-(b). Unbalanced
circuits are widely used in home-use compo-
nents, as they are simple and easy to design, In
this type of circuit. the ground line not only
serves for the negative signal flow but also
carries the direct current to drive the amplifier,
and often induced noise from external interfer-
ence sources, This approach therefore involves
a posstbility of sound quality degradation. The
more elaborate balanced approach on the other
hand requires two symmetrical, separate lines to
carry the hot" (posmve) and "cold" (negative)
signal with exactly opposite phase. An inherent
advantage of this principle is that it can cancels
out not only noise induced during the transmis-
sion process but also distortion components
arising Within the amplifier. This cancellation
takes place in the output circuits. leavmg only
the pure signal The balanced circuit configura-
tion therefore offers ideal conditions. The P402
features balanced signal transmission through-
out. from input to output, for clean power and
uncompromised performance,

The circuit configuration of the PTO? is shown in
Fig. 2. The top and bottom half are made up by
two exactly identical amplifiers arranged in par-
allel. one for the positive and one for the negative
input signal, The output power is derived from
the output terminals of the two amplifier units,
The signal supplied to the speakers conse
quently does not pass through the ground line,
The bridged connection has another advan-
tage, as even the slight distortion arising during
the amplification process is cancelled when the
signal passes the load (the speakers), The over-
all result is unsurpassed reproduction purity,

PARALLEL PUSH-PULL CLASS-A OPERA-
TION COMPLETELY ELIMINATES
CROSSOVER DISTORTION AND PROVIDES
AMPLE POWER RESERVES WrI'H 50 WATTS
PER CHANNEL INTO 8 OHMS AND70 WATTS
PER CHANNEL INTO 2 OHMS. DRIVE or
PRE-DRIVE STAGE EMPLOYS IDEAL MOS-
FET DRIVE.

Another distinguished feature of the P-102 is its
use of classA operation. This principle is ap-
plied not only to the input circuits. but it extends
right through to the powerful output stage The
total absence of crossover distortion preserves
the most subtle nuances and lets the music
emerge in unsurpassed detail. As can be seen
from Fig. 2. wide»band power transistors with a
maximum power dissipation (PC) of 80 watts
each are used in the output stage in a parallel
push»pull configuration, Therefore the total PC of
one amplifier unit is 320 watts. This enormous
power capacity is called upon to supply only one
half of the 50 watts of rated output power, Le, 25
watts. Effortless speaker drive even under the
most demanding conditions is the result of this
approach. The design also ensures that the
amplifier will remain stable even with very low
impedance loads, delivering a maximum output
of 70 watts per channel into 2-ohm loads. To
achieve this performance. the predriver stage
which sends the signal to the output devices is
also a vital aspect. It must possess low output
impedance and supply a high swing voltage to
the output stage This requires the use of high»
quality power-amplifying elements which can
withstand high voltages. In the P-102, the origi-
nal MOS-FET driver developed by Accuphase is
used. to provide a high-quality signal voltage
free from switching distortion to the output cire
cuits,

CASCODE PUSH-PULL DIFFERENTIAL IN-
PUT STAGE FOR FURTHER IMPROVED DE-
FINITION AT LOW LEVELS AND STABLE OP-
ERATION INTO THE HIGH FREQUENCY
RANGE.

In order to make full use of the performance
capabilities of the balanced class-A output cir~
suits. the amplifier's input stage must also con-
form to highest quality standards. To achieve
this aim, Accuphase uses a class-A cascode
push»puli differential circuit configuration in the
input stage of all its power amplifiers. As the
circuit diagram shows, the transistors Qla and
05, 02a and 06. Q1 b and Q13, 02b and OM in
the upper amplifier block are connected i a
cascade bootstrap configuration (the I@
block employs the same principle).

The cascade-connection principle was original»
ly developed for radio»frequency amplification.
It ensures stable operation over a wide range,
resulting in outstanding input linearity and wide
dynamic range,

TWIN MONO CONSTRUCTION USING TWO
MONOPHONIC AMPLIFIERS AND COM-
PLETELY SEPARATE POWER SUPPLIES
FOR LEFI' AND RIGHT CHANNEL

With class-A amplifiers, the power provtded by
the power supply is almost constant (except for
designs which modulate the bias voltage of the
output stage), and there is usually little interfer-
ence between the two stereo channels. To pre
vent even the slightest possibility of interfer-
ence. the P402 employs a dual monophonic
construction, In combination with the class-A
operation, this no-compromise design results in
ideal performance characteristics,

Page 6

STEREO POWER AMPLIFIER

r-ur sip-s .
r Inmtsflmotumisxmi

mum:
my-Mull

a II is r. H

mm» r m minim xu t».

o Froquoncy response

r. in

- Fowor output vs. THD (l-ohm lose)

0 PM output rut TND (Z-ohrm loot!)

This graph shows the transient intermoeuiatten uistonion (TIM)
spectrum. To measure this paramatar. a square wave or 3,15 kHz arid
a stne wave or is kHz are mixed and supplied to the input. The square
wave signal contains almost unlimited odd-number higher harmonics.
with oonrponenu at 9.54 kHz (third harmonic). 15.9 kHz (titth
harmonic). etc. When these components intermortuiate with the 154m:
signal. modulationprottucts show up at ireouencies where there is no
input signal. tor example at 5.45 kHl (15 kHz - 5.54 kHz). As the
reading oonnrnrs. there ere no distortion products at all above -r
which means that TM is less than 0.002%.

Hit: in satrwr

nut in

iuiruu
our
iwl ammo

arm n. ..

arr-or mums
tun . m.

rm treat .
mantra lemmuw .

err-tn LKVD. .
ll terror on tons

. . rs n u
mutant r en.

rlzwmu to w.

Thit graph shows the lnlermouulation distortion (IM) spectrum, as -
mammd by the IHF method. A IB-kHz and I 20ka signal are led to
the input. Any intenneduietion proouct oI thesa two signals would show
up at their iraquancy oillarenoe. to. 1 kHz. The reading continue that
such products are below «93 dB (00022?» Another intarmodulation
product would appear at 39 kHz. the sum or the two input signal
Imquefldes. Such distortion. Ivan II It cxlstad. would he

inconsequential because it is tar beyond the euoibie range. In the P-
102. this term at distortion Is also below -93 dB.

:rrn r'r ; ,r_|irln,~',ir . r- tr .«- l
. \l l

CONTINUOUS AVERAGE POWER OUTPUT
(Both channels driven. tiom 20 Hz to 20.000 Hz with no more
than 0.02% total harmonic distortion)
70 watts per channel. min, HMS. at 2 ohms
80 watts per channel, min. RMS. at 43 ohms
50 watts per channel. min, HMS. at 8 ohms
25 watts per channel, min, RMS. at is ohms

TOTAL HARMONIC DISTORTION
(Both channels driven. item 20 HZ to 20,000 H1)
0.02% max. at 2 ohms to 4 ohms
0.01% max. at 5 ohms to 16 ohms

INTERMODULATION DISTORTION
0.003%

FREQUENCY RESPONSE
20 Hz to 20.000 HZ: +0. -0.2 GB (Rated Output at the
maximum level control)
0.5 Hz to 200.000 Hz: +0. 43.0 dB (1 watt output at the
maximum level control)
05 HZ to 80.000 Hz: +0. -3.0 dB (1 watt output at -5 dB
attenuation)

VOLTAGE AMPLIFICATION IN DECIBELS
25.0 dB

OUTPUT LOAD IMPEDANCE
2 ohms to 16 ohms

DAMPING FACTOR
70

NPUT SENSITIVITV (It 0 ohm! laid)
0.8V (tor Rated output at the maximum level)
0.11V (tor 1 Wall output)

INPUT IMPEDANCE
BALANCED: 40k ohms
UNBALANCED: 20k ohms

Ar-WEIGHTED SIGNAL-TMOISE RATIO
(below Rated output. input shorted)
BALANCED: 120 dB
UNBALANCED; 112 dB
(1 watt output. terminated with 1k ohm)
BALANCED: 100 dB
UNBALANCED: 96 dB

POWER LEVEL METER
Logarithmic Scale Paak Laval indication oi the dynamic
range Item -40 dB to +3 05.

SEMICONDUCTOR COMPLEMENT
Bl Tts. 16 FETs. 8 K35 and 69 Dl's

POWER REQUIREMENT
Voltage selection; 100V. 117V. 220V and 240V. 50/60 Hz
Power consumptlon:
245w (Zero signal ouipui)
300W (Rated power output into 8 ohms load)

DIMENSIONS
Width 475 mm (18-11/16 inches). max. height 170 mm (at
11/16 inches). depth 403 mm (16-1/16 inches)

WEIGHT
2 kg (43.4 in) net. 25.5 kg (55.3 lo) in shipping carton

CCUPiTOSG

ACCUFHASE LABORATORY iNC.

A875Y

851-0070-00(GF) PRINTED IN JAPAN