Усилители мощности стерео — Rotel RMB-1555

The Rotel RMB-1555 is a five-channel Class AB power amplifier conservatively rated at 120 W per channel into 8 ohms with all channels driven. Rotel builds it around a high-current toroidal transformer and discrete output transistors, and it fits home theatre systems where a processor or receiver needs external amplification for five speakers.

Key specs that matter

Into 4 ohms the output rises to 170 W per channel with all five channels driven, and 4 ohms is the minimum speaker impedance Rotel specifies. Total harmonic distortion is below 0.03% from 20 Hz to 20 kHz, and intermodulation distortion is below 0.03% measured at 60 Hz and 7 kHz in a 4 to 1 ratio. Frequency response extends from 10 Hz to 100 kHz within plus 0.5 and minus 3 dB. Measured noise sits 116 dB below signal, IHF A-weighted, while damping factor is 180 and gain 26.5 dB. Input sensitivity is 1.5 V into an input impedance of 12 kohm.

Engineering and use context

Rotel explains its use of discrete output transistors by their better thermal stability compared with integrated circuit output devices, and describes the Class AB configuration as the balance it chose between power output and thermal efficiency. The toroidal transformer is specified for high current so that all channels can be driven at once without the output collapsing. The case measures 431 x 188 x 454 mm, has a 4U front panel height of 176.8 mm, and weighs 21.8 kg net, so a rack shelf needs to support that load. Power consumption is 650 W, and standby consumption drops to 0.5 W. The North American version is specified for 120 V at 60 Hz. For planning cooling in a closed cabinet, Rotel quotes a heat output of 1683 BTU/h at an eighth of full power. Because the rating is given with every channel working together, the figure describes the load of a full surround system rather than a single channel tested alone.

Pairing

A Rotel surround processor or receiver with preamplifier outputs can feed the five inputs directly, covering front left and right, centre and two surround speakers. Speakers rated at 6 or 8 ohm sit comfortably inside the minimum load limit.

Alternatives

The Rotel RMB-1506 is a six-channel Class AB alternative with 50 W per channel into 8 ohms, aimed at multizone installations.