Sonance Sonamp 260x3 Power Amplifier Review

Sonance, one of the pioneers of in-wall loudspeakers for multiroom installations, also manufactures amplifiers specifically designed for the requirements of such installations but (like the speakers) not limited to those applications. The amplifiers are marketed under the name Sonamp.

The Sonamp 260x3 is a high-cur-rent, 60-watt-per-channel stereo amplifier with a number of features that make it well suited for custom installations. It is designed to drive difficult loads, particularly the low impedances presented by multiple parallel-connected remote speakers. For convenience in operating multizone systems, the 260x3 has pushbuttons on its front panel for individual activation of its three pairs of speaker outputs. And the stereo line-input jacks on the rear apron are paralleled with a second pair for linking (“daisy-chaining”) additional amplifiers.

The Sonamp 260x3 is designed to drive 2-ohm loads without overheating or distortion (three paralleled 8-ohm speakers represent a load of 2.7 ohms). Its discrete output transistors are mounted on heat sinks, convection-cooled by air entering holes in the bottom plate and exiting through holes in the top cover.

The power supply uses a heavy toroidal transformer with 30,000 microfarads (μF) of filter capacitance. Several protection circuits and a relay safeguard the amplifier against overload, overheating, or output short circuits. The AC-line fuse on the rear apron is readily accessible to the user.

The Sonamp 260x3, finished in black, measures a compact 16-3/4 inches wide, 12-1/2 inches deep, and 3-1/2 inches high. It weighs about 16-3/4 pounds. In addition to the pushbutton power switch, the front panel has three speaker-selector buttons, two status-indicator lights, and individual channel-level controls that can be adjusted with a screwdriver through small holes in the panel.

The red power LED (marked A.C. ON) shows that the amplifier is plugged into a live outlet but not necessarily that it is turned on. The green LED (marked ACTIVE) indicates that the amplifier is switched on and operating.

A somewhat unusual (and useful) feature of the 260x3 is its Auto-On mode. If the small auto-on slide switch on the rear apron is set to on and the red power lamp is lit, the amplifier will turn on automatically within 1.5 seconds after a signal reaches its input connectors, lighting the green LED. About 2 minutes after all input signals are removed, the amplifier automatically shuts down and returns to its stand-by mode.

The Auto-On feature is particularly useful in multiroom installations, in which an amplifier may be located at some distance from the control center and signal source, since it eliminates the need for a remote power-switching system. But it is also handy in a singleroom installation, especially when the control unit doesn’t have enough switched outlets to handle the rest of the system.

The Sonamp 260x3 is rated for outputs of 60, 100, and 125 watts per channel into 8, 4, and 2 ohms, respectively, from 20 to 20,000 Hz at respective distortion levels of 0.05, 0.1, and 0.2 percent. The respective dynamic powers into those impedances are given as 85, 120, and 140 watts per channel. A-weighted signal-to-noise ratio (S/N) is 100 dB referred to rated output. Input sensitivity for rated output is 0.625 volt at maximum gain.

The Sonamp 260x3’s list price is $375. It is also available without the speaker switches, as the Model 260, for $325.

Lab Tests

The Sonamp 260x3’s input sensitivity was 80 millivolts (mv) for a 1-watt reference output at 1,000 Hz (0.62 volt for 60 watts). At the reference gain setting, the A-weighted noise level was —87.5 dB referred to 1 watt (-105 dB referred to 60 watts). The noise was mostly hum, with the 120-hz component in one channel measuring — 89 dB referred to 1 watt; the other channel’s hum was about 11 dB lower. Random noise was typically -100 to — 110 dB.

Preconditioning the amplifier at one-third rated power (20 watts into 8 ohms) for an hour left the top cover quite hot over the heat sinks, though not dangerous to the touch. At 1,000 Hz, the amplifier clipped at 94.5 watts per channel into 8-ohm loads, 144 watts into 4 ohms, and 208 watts into 2 ohms, corresponding to clipping-headroom figures of 2.0, 1.6, and 2.2 dB, respectively.

In dynamic power measurements, the maximum output was 115 watts per channel into 8 ohms, 190 watts per channel into 4 ohms, and 272 watts into 2 ohms, corresponding to dynamic headrooms of 2.8, 2.8, and 3.4 dB.

Frequency response was flat from 20 to 2,000 Hz, down 0.25 dB at 10,000 Hz, and down 0.76 dB at 20,000 Hz. At the amplifier’s rated output or less, distortion into 8 ohms was about 0.012 percent over most of the frequency range and a maximum of 0.058 percent at 60 watts and 20,000 Hz. The distortion at 1,000 Hz into 8 ohms was about 0.01 percent from less than 1 watt up to 90 watts. Into 4-ohm loads, it was about 0.02 percent up to 100 watts and just under 0.1 percent at 140 watts. The distortion into a 2-ohm load was less than 0.05 percent up to 200 watts.

We also made power-bandwidth measurements into each load impedance. This is a measurement of the maximum power available as a function of frequency without exceeding a given amount of distortion. With 8-ohm loads, the available power at 0.1 percent distortion was about 90 watts from 20 to 12,000 Hz, falling to 68 watts at 20,000 Hz. Into 4-ohm loads, the power at 0.2 percent distortion was 138 watts from 70 to 2,000 Hz, decreasing to 126 watts at 20 and 20,000 Hz.

Into 2 ohms, the power at 0.2 percent distortion was 230 watts from 80 to 2,000 Hz and 221 watts at 20 Hz, and it fell steeply above 12,000 Hz to 110 watts at 20,000 Hz.

Comments

We used the Sonamp 260x3 as a conventional single-output stereo amplifier. The Auto-On feature worked flawlessly and was so convenient that we wish it were available on other amplifiers.

The amplifier sounded as clean and free of noise and distortion as any of the conventional home amplifiers we have used. Although its measured distortion was somewhat higher than that of some other products, it was still far below the threshold of audibility.

The most notable aspect of the Sonamp 260x3’s performance was its ability to drive low load impedances without damage or degradation of performance (the increased distortion under those conditions is normal and characteristic of almost all amplifiers). The amplifier never shut down, overheated, or suffered any damage under our most severe test conditions.

In all fairness, most standard home amplifiers that have difficulties under similar conditions are not rated for 2-ohm operation (and sometimes not even for 4 ohms). Nevertheless, it is always a pleasure to find a product that goes well beyond the norms of performance, especially when there is no unreasonable cost penalty.

The Sonamp 260x3 is a rare example of a product designed for a specialized application that proves to be well suited for general use as well. It is moderate in price, compact in size, and attractively styled, and despite its relatively modest 60-watt rating, it’s a true powerhouse in actual use.

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