Усилители мощности моно — Krell Solo 375 XD

The Solo 375 XD is a Krell single-channel power amplifier built around the company's Class A iBias circuit in its revised XD form, which Krell introduced as an upgrade of the original iBias amplifiers. Being a monoblock, it handles a single speaker per unit, and the model sits below the Solo 575 XD in the same monoblock line.

Key specs that matter

Rated output is 375 W RMS into 8 ohm and 600 W RMS into 4 ohm, with 154 V peak to peak or 55 V RMS available at the terminals and a peak current of 17 A. Gain is 27 dB, and an input level of 2.45 V RMS on either the RCA or the XLR socket drives the amplifier to full power. Input impedance is 100 kohm single-ended and 200 kohm balanced. The response holds within 0.15 dB from 20 Hz to 20 kHz and reaches from 0.5 Hz to 100 kHz at the 3 dB points. Harmonic distortion stays under 0.03% at 1 kHz and 375 W into 8 ohm and under 0.19% at 20 kHz. Noise is more than 103 dB down wideband unweighted, referred to full output, and better than 114 dB A-weighted. Output impedance is below 0.018 ohm across the audio band, giving a damping factor above 440 referred to 8 ohm, and slew rate is 40 V per microsecond.

Engineering and use context

In a classic Class A stage the bias current stays high whatever the music demands, which wastes energy as heat. The iBias circuit measures the current flowing to the speaker and adjusts the bias continuously, so the transistors keep Class A operation while only drawing what the signal needs at that moment. The practical result shows in the consumption figures - 1 W in standby, 66 W at idle and 1150 W at maximum output. The chassis measures 434 mm wide, 194 mm high and 536 mm deep and weighs 27.3 kg on its own or 31.8 kg packed. Beside the RCA and XLR inputs there is a Krell CAST input, the brand's current-mode link for connecting Krell sources and preamplifiers, and the output side carries speaker binding posts.

Pairing

Any preamplifier whose balanced outputs reach the rated input level drives the amplifier to its rated output, and a Krell preamplifier with a CAST output can use the current-mode connection instead. The low output impedance and high peak current suit loudspeakers whose impedance falls towards low values. Stereo use requires two of them, and the rack or floor must hold two chassis of this footprint.

Alternatives

The Krell Solo 575 XD is the larger monoblock in the same XD range, rated at 575 W with the same iBias XD circuit.