Pioneer a 27 owners manual

Page 1

STEREO AMPLIFIER

' A-27

OPERATING INSTRUCTIONS S/G

NOTE

This amplifier provides a line voltage selector switch on the rear
panel, so please confirm the setting of the switch before turning

on the power switch, referring to the section Adjusting the Line

0» DIONEER. Voltage Selector Switch on page 15.

Page 2

INSTALLATION PRECAUTIONS

The A27 weighs a full 26kg and so be sure to
install it in a location which can support
heavy weights. Also, take care when trans-
porting the A-27 from one place to another
and when otherwise handling it.

Dont put anything on the top of the A-27
because a high-power amplifier will produce a
lot of heat. Also leave sufficient space around
the amplifier for adequate ventilation.

CONTENTS

Features .......................... 2
Stereo System Composition ........... 4
Installation Cautions ................ 4
Connection Diagram ................. 5
Connections ....................... 6
Front Panel Facilities ................ 8
Operations ........................ 10
Effective Operations ................. 11
Using the Tape Decks ................ 13
Using the PRE OUT,

POWER AMP IN jacks ............. 14
Conditions Frequently Mistaken

for Malfunction .................. 16
Specifications ................. Insertion
Characteristics Charts ........... Insertion
Schematic Diagram ............. Insertion

FEATURES

Power Amplifier with a Magni-wide Power Range,
Low Distortion and Continuous Power Output of
120W Per Channel

The A-27 stereo amplifier incorporates a current mirror
load cascade connected to a single-stage differential ampli-
fier with dual transistors, a Class AB triple-stage Darlington
circuit, a parallel push-pull circuit and a pure comple-

mentary OCL circuit.

Pioneers newly developed Ring Emitter Transistors (RETs)
with excellent high-frequency-range characteristics at high-
output power ratings are adopted for the Class AB power
stage. These help the amplifier display an ultra-wide power
range and deliver a

Continuous Power Output of 120 watts* per chan-
nel, min., at 80th from 5Hertz to 30,000
Hertz with no more than 0.012% total harmonic

distortion.

The power amplifier is configured as a DC power amplifier
with the capacitors removed from the NFB circuit for a
superbly low distortion all the way from very faint outputs
up to full power.

In the output range which is actually used (SW/8 ohms),
the power amplifier works as a Class A model, enabling
you to enjoy music delivered by a Class A amplifier with
magnificient linearity.

Independent Left and Right Power Supplies that
Back Up the High and Stable Power Output

The large-sized transformers with their superb regulation
packing quite a punch, and the large-capacity (18,000pF)
electrolytic capacitors (two per channel) are featured in the
independently positioned dual power supply circuits with
separate power transformer windings to provide power for
the left and right channels. These power supplies not only
deliver a stable output of power at all times but they also
help give low-frequency-range sound reproduction with an
unusually singular regulation and damping even during high
outputs.
The primaries of the power transformers contain inrush-
current suppressors which serve to suppress high-value
inrush currents when the power switch is thrown to ON.
These circuits reduce the load on each of the parts that
make up the dynamic power supplies, and also successfully
enhance the degree of reliability.