Krell S-550i

The S-550i is the larger of two new integrated amps from Krell. Both of these amps feature circuit boards that utilize surface mount components. This means they can pack more power into smaller chassis than ever before. The S-550i is rated at 275 watts per channel into 8 ohms, and that doubles to 550 wpc into a 4 ohm load. This being from a box that is less than 6 inches tall. So now you can get tons of Krell goodness in a small package and at a very affordable price.

For the uninitiated, Krell has been around for almost 30 years now, producing fine sounding equipment with a rugged, industrial look. Some of the all-time best systems I have ever heard were built around Krell amplification and digital source components.

The S-550i embodies many of Krell's famous design features from their past amplifiers. Let's first begin by taking a look at the preamp stage. The preamp circuit is pure Class A biased and fully balanced. The architecture of this circuit is Krell's proprietary Current Mode topology which is a very high bandwidth design: Krell rates the preamp section as flat to 1 MHz!

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Design: Fully Balanced Differential Class A/B Integrated Amplifier
Power Output: 275 wpc (8 Ohms); 550 wpc (4 Ohms)
THD: <0.025% at 1 kHz
Frequency Response: 20 Hz - 20 kHz +0, -0.08 dB
Inputs: 1 Balanced XLR, 3 Unbalanced RCA, 1 iPod 30-Pin Connector
Outputs: 1 Pair Pre Out RCA and 1 Pair Speaker
Input Impedance: Balanced 95 kOhms; Single-Ended 47.5 kOhms
Output Impedance: <0.073 at 20 Hz; <0.08 , 20 Hz to 20 kHz
Damping Factor: >110 at 20 Hz (8 Ohm Load); >75, 20 Hz to 20 kHz (8 Ohm Load)
Dimensions: 5.84 H x 17.26W x 17.70 D
Weight: 64 Pounds

See also link.