Delivering 275 watts of stereo output, the S-550i is a power source for virtually any speaker on the market while occupying a fraction of the space typically required for a system delivering this sound quality. The S-550i is outfitted with balanced and single-ended inputs, iPod dock, and Theater Throughput™ mode. Developed by Krell, Theater Throughput™ simplifies integration into home theater systems. For custom integration applications, 12 volt triggers, RS-232 connectivity and rack mount ears are included. Operational parameters can be customized via the menu system that is accessible from the front panel or the included brushed Aluminum remote control.
The preamplifier section features circuit concepts from Krell's flagship Phantom preamplifier. Krell Current Mode provides unequaled bandwidth for the most revealing playback of today's high resolution music sources. Direct coupled circuitry eliminates impact-robbing capacitors from the signal path and an elegant, custom-machined level control adjusts volume. Discrete circuitry, in a balanced topology, is afforded its own power supply regulation. All signal gain is realized using surface mount technology featuring proprietary current mirrors with nearly 500 times the open loop linearity of other designs. Negative feedback is not used anywhere in the preamplifier, nor is it necessary. Open-loop distortion is typically less than 0.003%. The volume control is realized with a balanced resistor ladder - bandwidth and transient response of the preamp circuitry are virtually unaffected by the volume setting.
Power Amplifier Highlights
The S-550i packs a massive 1,750 watt transformer and 68,000μF of capacitance into an elegant 5" high chassis. This power supply feeds classic Krell circuitry throughout the topology using only discrete circuitry. As with all Krell amplifiers, the S-550i design is an ideal voltage source. That is, the S-550i doubles its power output when a speaker's impedance is halved. For the S-550i, the results are 275 watts into 8 Ohms and 550 watts into 4 ohms. This capability is essential for realistic reproduction of a recording's dynamic content. Most amplifiers can't deliver this power doubling, leaving music sounding compressed and lifeless.