Yamaha XS250 H **

The Yamaha XS250 Power Amplifier offers an ideal balance of performance, power, and economy for a wide range of professional applications - from on-the road sound reinforcement to permanent installations in clubs, houses of worship, and other institutions. In addition to a plentiful supply of clean, precise power and advanced features, these high-performance amplifiers also offer the type of hard-working dependability that is essential for demanding professional applications.

The XS250 and XS350 are proof that, where Yamaha is concerned, economy does not mean compromise. These deliver top-of-the-line power and performance while being remarkably affordable. The XS250 offers 170 watts per channel, and the XS350 puts out a solid 230 watts, respectively. But power alone does not make up the entire picture: total harmonic distortion in both amplifiers is no more than 0.05% at half power so you get clean, precise sound.

If you need serious power, both models can instantly be switched to the BRIDGE mono operation via a rear-panel selector. In the BRIDGE mode the XS250 delivers 500 watts, and the XS350 delivers 700 watts with the same low distortion and high sound quality as in the normal stereo mode

The mode selector also features a PARALLEL setting in which the amplifier's two channels deliver independent output to drive separate speaker systems, but are fed from a single mono signal applied to the "A" input.

To eliminate the need for extra equipment and cabling, and make setup as easy and convenient as possible for a wide range of system configurations, the XS250 and XS350 feature built-in filters which shape the amplifier's frequency response for driving subwoofer systems. Independent filters are provided for the "A" and "B" channels, and the filter frequency of each is continuously variable from 25 Hz to 125 Hz for optimum matching with any type of subwoofer.

Alternatively, a switchable Low Cut mode allows the filters to be used to remove low-frequency noise and rumble.

Input attenuators on the amplifier's rear panel allow optimum matching with just about any input source. The fact that the attenuators are on the amplifier's rear panel - rather than the more common front-panel location - means that they are out of the way, to prevent accidental level changes and tampering. The attenuators are dB-calibrated and have 31 detent positions for accurate, repeatable settings.

Comprehensive circuit protection in both models ensures safe operation with minimal possibility of accidental damage to speakers or the amplifiers themselves. Power-on muting prevents the power-on surge from reaching the speakers and allows the amplifier to stabilize before operation begins. DC sensing shuts off the outputs if excessive DC is detected at the output terminals. And thermal protection shuts down the amplifier if the heat sink temperature exceeds 90 degrees Celsius.

When it comes to power amplification, heat can degrade reliability perhaps more than any other factor. Extra measures have been taken in the XS250 and XS350 to ensure trouble-free operation under even the worst conditions. Both models feature oversized heat sinks, an interior layout carefully designed to promote optimum air flow and heat dispersion, and a high-reliability variable-speed cooling fan which responds to heat-sink temperature to maintain optimum operating temperature at all times.

The XS250 and XS350 offer multiple input and output connectors for plug-in compatibility with the widest possible range of systems and equipment. Both balanced XLR-type connectors and barrier-strip connections are provided for input. For speaker connection the XS250 and XS350 provide both barrier strip and 5-way binding post terminals.