Plinius SA-250 Owners manual

Class A Power Amplifier

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CONGRATULATIONS

CONGRATULATIONS on your decision to become the proud owner of this

CONGRATULATIONSCONGRATULATIONS

Plinius SA-250 Power Amplifier.

This manual has been prepared to help you understand the operation of your amplifier, and to provide
information about its design and the variety of ways it may be used.

We have designed and manufactured this amplifier to reproduce faithfully and accurately, your favourite
music. With a little care and a full understanding of the operating recommendations in this manual, your
Plinius SA-250 Power Amplifier will provide years of high-quality, trouble-free performance.

Serial Number: ..................................................................................

Date of Manufacture: ..................................................................................

Final Test Certified By: ..................................................................................

IMPORTANT: PLEASE TAKE THE TIME TO READ THIS MANUAL

THOROUGHLY BEFORE USING YOUR AMPLIFIER.

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Introduction ........................................................................................................................................Page 3

Precautions ........................................................................................................................................Page 5

Amplifier Features - FRONT PANEL .....................................................................................................Page 6

Amplifier Features - REAR PANEL .......................................................................................................Page 8

Amplifier Configuration Selector (ACS) ...............................................................................................Page 9

Balanced/Unbalanced Signals ..........................................................................................................Page 10

Installation and Operation .................................................................................................................Page 12

Input/Output Connection ...................................................................................................................Page 13

RCA Connection ...............................................................................................................................Page 14

XLR Connection ................................................................................................................................Page 15

SA-250 Features ..............................................................................................................................Page 17

Loudspeaker Selection .....................................................................................................................Page 19

Why Class A is better .......................................................................................................................Page 20

Specifications ..................................................................................................................................Page 21

Index ................................................................................................................................................Page 22

Contact Details .................................................................................................................................Page 23

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Please take special note of the following precautions before operating your new amplifier:

• The Plinius SA-250 Power Amplifier can be operated in bridged mode and may deliver in excess of
900 watts into 8 ohms. This amplifier is also capable of a very large peak current delivery.

• The Plinius SA-250 Power Amplifier operates in Class A. It is capable of generating temperatures that
could have an adverse effect on other equipment, furniture etc. DO NOT leave flammable material on
the amplifier whilst running, as this could pose a serious fire risk.

• The Plinius SA-250 Power Amplifier is of direct-coupled design, and offers no protection from
preamplifiers that have a high DC component at their outputs.

• This amplifier operates at hazardous voltage levels. We recommend that any work requiring removal
of the lid or base of this amplifier be referred to a suitably qualified and experienced service
technician.

• DO NOT attempt to connect any input of this amplifier to it’s own outputs.

• DO NOT earth any output terminal or connect any of these terminals together without following the

instructions in this manual or seeking qualified assistance.

• DO NOT place this amplifier in any position where liquids or any foreign material may accidentally
enter it.

• DO NOT connect any voltage source, short circuit, earth/ground or appliance (other than suitable high
fidelity loudspeakers) to the amplifier output terminals.

• Some preamplifiers, processors, CD players’ etc. produce large switching pulses when switched on
causing a loud click through the loudspeakers. For this reason, turn on all other equipment in your
system before turning on your Plinius SA-250, or ensure that the amplifier is in MUTE. You will not
experience this phenomenon with Plinius Preamplifiers.

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The front of the Plinius SA-250 Power Amplifier incorporates a small panel fitted with three switches.
These switches control the functions most used on the amplifier.

MUTE

F

RONT PANEL LAYOUT SHOWING MUTE

The operation of these switches is, from the left:

, M

AINS AND BIAS SWITCHES

A BIAS

MUTE SWITCH

It is not recommended practice to interfere with the input cables while the amplifier is switched on and
connected to the loudspeakers, so a Mute switch is fitted to interrupt the input signal. This allows you to
connect and disconnect the input cables without the necessity of turning the amplifier off.

The switch operates on a pulse system in conjunction with an LED indicator. When the amplifier powers
up from start, the Mute automatically engages and has to be switched for normal listening. The Mute
switch also disconnects the speakers while the LED is on. Take care not to touch any terminals other than
the outputs when changing the output (loudspeaker) leads.

MAINS SWITCH

This heavy-duty rocker switch in the centre of the panel turns the Mains/Line Power to the amplifier ON or
OFF. An LED in the centre of the front panel indicates that the power is on. When first switched on the
power LED will pulse for ten seconds - this is an initialisation sequence, after which the power LED
remains lit. The amplifier draws a moderately high current when switched on. Despite the "Soft Start
Circuit" within the amplifier reducing current demand on the mains as the amplifier is switched on, it is
not good practice to rapidly turn the Mains switch on and off repeatedly.

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BIAS SWITCH

This switch on the right of the panel alters the operating bias of the amplifier. The switch operates on a
pulse system and lights the Bias LED when the amplifier is switched to Class A. In Class AB the LED is
off.

BIAS AB:

BIAS AB: This position reduces the bias on the output stage to operate the amplifier in Class AB. This is

BIAS AB:BIAS AB:
a bias configuration used by the majority of high fidelity amplifier designers for their products. In Class
AB your Plinius SA-250 produces very high quality sound, suitable for all occasions where ‘super critical’
listening is not a priority. The quality of performance in this mode may exceed that of many other
amplifiers so a dual benefit exists in that this facility provides the user with a much cooler operating
temperature, and a much reduced demand on electricity particularly at idle (while the amplifier is not
reproducing music). This unique feature allows you to leave the Plinius SA-250 switched ON at all times,
rendering the amplifier ready for use and requiring only a few minutes of warm-up in Class A before the
very best of the amplifier's sonic qualities may be experienced.

BIAS A

BIAS A:::: This position provides a true Class A bias to the output stage therefore ensuring the optimum

BIAS ABIAS A
performance of the amplifier during all listening events. Class A amplifiers run hotter than Class AB
amplifiers, hence our specially designed and distinctive heat sinks. Operating the amplifier in BIAS A
necessitates two precautions that should be observed.

1.

1. On switching to BIAS A, the temperature of the amplifier will quickly increase and the amplifier will

1.1.

become quite hot. Once again we remind you to ensure that you have left adequate space around
the amplifier for ventilation. Ensure that no objects are resting on the amplifier and check that the
heat sink (cooling fins) are not obstructed in any way.

2.

2. The current required from the mains supply in BIAS A is approximately 1,000 watts, similar to a

2.2.

small electric heater. The amplifier should not be connected to a wall outlet that is shared with
other heavy current appliances such as heaters or electric motors. If in doubt, check with your
Plinius dealer for advice.

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