Krell ksa 250 owners manual
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2A. GENERAL INFORMATION The latest generation of high-resolution source components and speakers places new demands on the power amplifier. The Krell KSA 150 and KSA-250 meet these challenges with fresh design sophistication and long-term value. Both products can drive any speaker with an effortless quality that makes their power seem endless. Extreme clarity is maintained at all power levels. They both utilize Krell refined high-bias Class A and direct-coupled circuitry from input to output. Their power supplies and output stages are massive. High voltage rails with extensive regulation are provided for the input circuitry. All materials and electronic components are of the finest quality and operate within their optimum performance ranges. Virtually all hand wiring has been eliminated, resulting in a dramatic improvement in sonic clarity. The KSA-150 and KSA-250 both utilize Class A circuitry throughout the audio and power supply regulation stages. Class A gain stages deliver excellent sonic performance under diverse conditions because all active components are turned on at all times. This allows each component to operate in its most linear and precise regions. The amplifiers are able to respond to the full range of input signals with equal accuracy. The KSA-150 and the KSA-250 are conservatively rated at 150 and 250 watts per channel into 8 ohms, respectively. The 150 will actually generate 220 watts into 8 ohms, and the 250 will generate 320 watts into 8 ohms. The 8-ohm power ratings do not account for the amplifiers superb sonic performance nor describe their maximum power. The Krell definition of power and the ability to drive low impedances is that the output must double into successively low impedances. The immense power supplies in both products allow them to double their power into one ohm. There are many advances in thermal construction and control circuitry in the KSA -150 and KSA -250. All heat bearing structural components and external heat sinks have been designed in-house to improve thermal tracking and cooling. This construction provides very low thermal resistance between the output transistors and the heat sinks, resulting in superior thermal tracking. It also results in a considerable reduction in overall size. Greater amplifier life expectancy is an added design benefit. Automatic self-adjusting bias and DC offset control circuitry have been developed for the KSA-150 and the KSA-250. These circuits compel the amplifiers to conform to their intended operational parameters under all AC mains conditions. A variation of approximately 10% in the AC can generally be accommodated, guaranteeing consistent performance in all environments. The KSA-150 and KSA-250 are protected by a series of opto-coupled, non- intrusive circuits that constantly evaluate the amplifiers operation. Appropriate
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3protective action exists for a wide range of problematic conditions. Collectively, the protection circuitry is designed to avoid damage caused by other defective components, faulty wiring, mishandling of the system or amplifier failure. Krell is committed to balanced operation in all products. Balanced systems have long been standard in professional audio applications and the same advantages apply to home audio equipment. There is a 6dB increase in gain without an increase in noise and there is a decrease in overall system noise caused by stray AC and RF fields. Sonic performance is drastically improved, particularly in dynamic and soundstage presentation. B. POWER CONSIDERATIONS The KSA-150 is rated as delivering 150 watts per channel into 8 ohms. The amount of Class A power is adjusted for the finest sonic performance with a minimum of generated heat and energy consumption. The amplifiers maximum power into 8 ohms is 220 watts per channel. The KSA-250 is rated as delivering 250 watts per channel into 8 ohms. The amplifiers maximum power into 8 ohms is 320 watts per channel. That every Krell product uses Class A circuitry in all gain and supply stages is a foundation of our design philosophy. A second design commitment that relates to amplifiers is that every unit be capable of doubling its output into successively lower impedances. The KSA-150 will deliver 300 watts per channel into 4 ohms, 600 watts per channel into 2 ohms and 1,200 watts per channel into 1 ohm. The KSA-150 is fully capable of driving impedances below 1 ohm. The KSA-250 will deliver 500 watts per channel into 4 ohms, 1,000 watts per channel into 2 ohms and 2,000 watts per channel into 1 ohm. The KSA-250 is capable of driving impedances below 1 ohm. Given the above, the AC power supplied to the amplifier is crucial to getting maximum performance. The KSA-150 will operate at its peak with a dedicated 20- amp line, although this is not a requirement. Additionally, the KSA-150 should only be operated with the power cord supplied with the unit. Use of other power cords may damage the amplifier and void its warranty. The KSA-250 requires a dedicated 20-amp line. It too, should only be operated with the power cord supplied with the unit. Please consult Krell or your dealer before using any devices designed to alter or stabilize the AC power for the KSA-150 or KSA-250. C. UNPACKING Remove the unit, power cord and accessories from the shipping container. Store all packing materials in a cool, dry place for future use. Inspect the unit for shipping damage. If any damage is evident, contact your dealer immediately. If the unit is in proper condition, proceed with the installation.