Russound P125 Dual Source Power Amplifier — Installation Manual

Installation manual for the Russound P125 Dual Source Power Amplifier — a 2-channel, 125-watt-per-channel amplifier with auto-source switching, speaker-level input, and bridged-mono capability for whole-home audio distribution.

Overview

The Russound P125 is a 2-channel dual source power amplifier with auto-source switching. It features Primary and Secondary audio line inputs with a loop-out to another zone, receiver, or device from the secondary source. A speaker-level input can be connected and assigned as either the primary or secondary source. This amplifier is well suited for power upgrades in zones with large speaker selectors or volume control systems.

• Rated at 125 watts per channel into 4 ohms, 80 watts into 8 ohms
• Bridge Mono mode combines channels for 250 watts into a single 8-ohm load
• 12V Trigger In/Out allows activation by (or of) other devices via a 3.5mm mini phone plug cable, 100mA current capability
• Robust output-channel protection circuitry for reliability under extreme conditions

Thermal & Short-Circuit Protection

The P125 includes special circuitry to safeguard against thermal overload, which engages only after extended high-volume operation without adequate ventilation and/or with speaker impedances below the minimum rating. In thermal protection mode the amplifier automatically stops output — turn off the amplifier, check speaker impedance and ventilation, and power back on once it has cooled.

Similarly, short-circuit protection engages if a faulty speaker causes a short. Turn off the amplifier, check speakers for shorts, and cycle power to return to normal operation.

Front & Rear Panel Controls

• Power — front panel switch manually turns power on/off.
• Speaker selector — select speaker pair A (main) or B (auxiliary). A and B can be used together as long as speakers are minimum 8-ohm impedance.
• Power LED indicator — RED = ON/Standby, AMBER = 12V Trigger switched on.
• Balance — adjusts output balance between right/left channels; default is centered.
• Volume — adjusts speaker output volume. In Bridged mode, set to minimum first, then adjust up.

Power On — Manual, Auto, Remote

Set the rear-panel switch to Normal for manual power on/off via the front Power button. Set to Auto On to have the amplifier power on automatically when music is sensed on any input (it powers off after about 4 minutes of silence). Set to Trigger and connect a 3.5mm phone-plug wire to the 12V Trigger In to power on remotely. Note: the front-panel Power button must be in the "On" position for 12V trigger and Auto On to work.

Speaker Cable

Use a minimum 16 gauge and maximum 12 gauge stranded copper cable, avoiding stray strands, and keep polarity consistent.

System Configuration — Stereo Mode

The P125 can be configured as a power upgrade for specific zones, for use with large speaker selectors, and for long parallel speaker runs (outdoor zones).

Single Source Connection

1. Unplug the amplifier.
2. Set the Stereo/Bridge switch to Stereo.
3. Connect the audio line output from a stereo preamplifier or source to the left/right Secondary input jacks. If the output is only available as speaker level, see Speaker Level Signal below.
4. Connect speakers to the terminals, observing proper polarity.
5. Restore power. Each channel's level can be adjusted with the corresponding level control.

Dual Source Connections

Connect the source you want to take temporary priority to the Primary input, and the constant source to the Secondary input. Whenever the primary source becomes active, its signal takes priority over the secondary line (which stays active but unheard) until the primary signal is muted or turned off, at which point the amplifier automatically switches back to secondary.

1. Connect source audio outputs to both Primary and Secondary inputs.
2. Set the switching delay with the Delay Time knob — this determines how long it takes to switch back to secondary (e.g. increase delay if the primary source is a CD changer, to avoid switching back during disc changes). Works with line-level or speaker-level signals.

Speaker Level Signal

If a source is only available as a speaker-level signal, connect it to the Speaker Level Input terminals using the 5-way binding posts, observing proper polarity. Only one set of speaker-level inputs can be assigned by the selector switch, and set the switch to Primary or Secondary to force the input's role.

System Configuration — Bridged Mode

Combines left and right channels for a higher-power mono output.

1. Unplug the amplifier.
2. Set the Stereo/Bridge switch to Bridge Mono.
3. Connect the line-out from a preamplifier/source to the Left and Right Secondary input jacks — the P125 sums the two channels into a mono signal.
4. Connect the speaker cable's negative (-) lead to the R(+) terminal and positive (+) lead to the L(+) terminal (per rear panel markings). An 8-ohm minimum load is recommended.
5. Restore power.
6. Equally adjust the Master Level right and left.
7. Set the front-panel Balance control to Center.

For proper operation, the Master Level left/right adjustment should be set to center before starting, then adjusted from there.

System Configuration — Basic Speaker Connection

The P125 has a minimum 4-ohm load in stereo mode. Connect up to one pair of 8-ohm speakers on A and one pair of 8-ohm speakers on B (e.g. living room on A, dining room on B).

System Configuration — External Volume Control

The P125 can drive multiple pairs of speakers with impedance-matching volume controls and/or speaker selectors. Connect up to eight total impedance-matching autoformer-based volume controls to the amplifier on the speaker A connection only.

Clearance Requirements

Keep the clearances specified in the manual around the amplifier for proper ventilation. Avoid mounting under kitchen cabinets, in direct sunlight, near heat sources, or in damp/dusty locations.

Technical Specifications

Warranty

The Russound P125 Amplifier is guaranteed against defects in materials and workmanship for one (1) year from the date of purchase. Russound will replace defective parts and correct workmanship defects without charge for parts or labor, provided the unit is installed and used per written instructions and returned to Russound at the owner's expense with prior written permission. The warranty does not cover damage from abuse, accident, misuse, negligence, improper installation, power surges/lightning, normal wear, or unauthorized alteration. Call Russound at (603) 659-5170 for a Return Authorization number before returning a unit.