Class A /AB switchable
BIAS AB: This position reduces the bias on the output stage to operate the amplifier in Class AB. This is 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: This position provides a true Class A bias to the output stage therefore ensuring the optimum 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.
The current required from the mains supply in BIAS A is approximately 1,000 watts, similar to a 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.

AMPLIFIER CONFIGURATION
RCA INPUTS LEFT & RIGHT: These standard RCA terminals are for use with unbalanced signals from most signal sources such as audio preamplifiers.
XLR BALANCED INPUTS LEFT & RIGHT: XLR connectors fitted to this amplifier are for use with balanced line signals from audio preamplifiers. Balanced signals are carried via a three way cable that connects all three pins at each end of the interconnect cable.
AMPLIFIER CONFIGURATION SELECTOR (ACS)
The Amplifier Configuration Selector (ACS) is a unique switching method that exploits all of the operational features of your Plinius SA-250 Power Amplifier. By using this switch it is possible to operate your amplifier with either balanced or unbalanced signals and achieve a stereo or mono output.
Stereo or Mono use of this amplifier will depend on the type of ancillary equipment employed with your system. If you wish to use this amplifier as a single channel (mono) Power Amplifier in a stereo high fidelity system, then another SA-250 will be required for the other channel. This will provide an extremely high performance option.
RCA STEREO XLR BALANCED MONO RCA BRIDGED MONO XLR STEREO
* ALL MONO/BRIDGE OPTIONS USE RIGHT INPUT AND LEFT + RIGHT + OUTPUTS ONLY
AMPLIFIER CONFIGURATION SELECTOR REFER TO OWNER’S MANUAL FOR TECHNICAL DESCRIPTIONS
AMPLIFIER CONFIGURATION SELECTOR
The ACS switch options are:
RCA STEREO: This option provides a stereo output via both left and right output channels from a stereo signal connected to both left and right input RCA inputs.

RCA BRIDGED MONO: This option configures your amplifier to drive one loudspeaker from one unbalanced signal fed to the RIGHT RCA input. The loudspeaker is connected to both channels positive (+) output terminals, giving an available power in this mode four times the rated output of the amplifier, approximately 900 watts into 8 ohms. Special care must be taken in connecting the input signal and loudspeakers to ensure safe operation and best possible performance.

XLR STEREO: This option provides a stereo output signal from a balanced stereo input signal connected to both the left and right XLR inputs. All the advantages of balanced line transmission will be realised with good rejection of noise and some freedom from earth or ground loops (hum).
XLR BALANCED MONO: In this mode both channels of your Plinius SA-250 combine to operate as a true balanced mono amplifier, from input to output. This configuration provides the highest quality mono performance from a balanced line input connected to the RIGHT BALANCED XLR INPUT. As with RCA Bridged configuration, the loudspeaker is connected to both channels positive (+) output terminals. Available power in this mode is four times the rated output of the amplifier, approximately 900 watts RMS into 8 ohms. Special care must be taken in connecting the input signal and loudspeakers to ensure safe operation and best possible performance.
BALANCED/UNBALANCED SIGNALS
Balanced or unbalanced input options will depend on the type of signal available from your preamplifier or other equipment. The Plinius SA-250 provides both options to allow you to choose the most suitable preamplifier for your purposes. Plinius Preamplifiers offer both balanced and unbalanced output options.
BALANCED LINE is normally used to transmit signals in a professional environment. Because balanced line effectively reduces or eliminates noise pick-up by the system cabling, it has become increasingly more important in high-quality domestic high fidelity systems.
UNBALANCED leads such as single ended, RCA or coaxial are common and are used in the majority of audio signal systems. The terminal plug and socket are most commonly called RCA and can be found on your Plinius SA-250 for use as the standard input terminals for both left and right inputs.
OUTPUT TERMINALS – STEREO
Output connections for the loudspeakers are provided on the left and right hand side of the rear panel. Two parallel pairs of binding posts for each channel are fitted – these provide ease of use with bi-wiring and multiple cables requiring a large contact area.
OUTPUT TERMINALS – BRIDGED/MONO
In bridged/mono modes, the loudspeakers utilise only the positive (+) outputs of your Plinius SA-250. In this configuration power output to the loudspeakers is dramatically increased (around four times as much), and is commonly used in conjunction with another amplifier for amplification of each channel from the preamplifier.