MEASUREMENTS

Iperformed a complete set of measurements on one of the Linn Klimax Solo 800s (serial number 1593390) with my Audio Precision SYS2722 system.1 I preconditioned the Solo 800 by following the CEA’s recommendation of running it at one-eighth the specified power into 8 ohms for 30 minutes. At the end of that time, the temperature of the top panel was just 81.6°F (27.6°C) and that of the side-mounted heatsinks only slightly higher, at 89.0°F (31.7°C). The Linn amplifier runs cool, especially considering its high rated power.

The Linn amplifier’s balanced and singleended inputs both preserved absolute polarity. (The XLR jack is wired with pin 2 positive.) Linn doesn’t specify the Solo 800’s input impedance—I measured a reasonably high 7760 ohms from 20Hz to 20kHz for the balanced input, 9930 ohms at 20Hz and 1kHz and 9600 ohms at 20kHz for the unbalanced input. The voltage gain at 1kHz into 8 ohms was 22.4dB balanced and 28.44dB single-ended; these values are close to the specified impedances of 22.6dB and 28.6dB, respectively.

The output impedance, including the series impedance of 6' of spaced-pair cable, was a relatively low 0.17 ohms at 20Hz and 1kHz, rising slightly to 0.187 ohms at 20kHz. As a result, the variation in the frequency response with our standard simulated loudspeaker2 (fig.1, gray trace) was minimal, at ±0.12dB. The response into resistive loads was flat in the audioband, not reaching –3dB until 90kHz into 8 ohms (blue trace). The rise in output impedance with increasing frequency means that into 2 ohms, the output was down by 3dB at

63kHz. With its wide small-signal bandwidth, the Linn’s reproduction of a 10kHz squarewave into 8 ohms featured very short risetimes (fig.2) with no overshoot or ringing.

Although low-level ultrasonic noise was present in the Solo 800’s output—this was not affected when I connected the grounding terminal on the amplifier’s rear panel to the Audio Precision’s chassis ground— the unweighted, wideband signal/noise ratio (ref. 1W into 8 ohms), taken with the single-ended input shorted to ground, was a good 65.6dB. This ratio improved to an excellent 95dB when the measurement bandwidth was restricted to 22Hz–22kHz and to 99dB when A-weighted. Spectral analysis of the low-frequency noisefloor while the Linn drove a 1kHz tone at 1W into 8 ohms (fig.3) revealed very low levels of both random noise and of AC supply–related spuriae.

Linn specifies the Solo 800’s maximum power as 400W into 8 ohms, 800W

into 4 ohms (both powers equivalent to 26dBW), and 1.2kW into 2 ohms (24.8dBW).

Stereophile defines an amplifier’s clipping power as when the THD+noise reaches 1%. With that criterion, the Solo 800 slightly exceeded its specified powers into 8 ohms (410W, 26.1dBW, fig.4), into 4 ohms (805W, 26.05dBW, fig.5), and into 2 ohms (1260W, 25.0dBW, fig.6). These high clipping powers were achieved even though the wall voltage had dropped from 117V AC with the amplifier idling to 113.6V AC at clipping into 2 ohms.

The downward slope of the traces at low powers in figs.4–6 is due to actual distortion lying beneath the random noisefloor.

I therefore examined how the THD+N percentage varied with frequency at 20V, which is equivalent to 50W into 8 ohms, 100W into 4 ohms, and 200W into 2 ohms. The THD+N percentage was very low into 8 ohms (fig.7, blue trace) but slightly higher into 4 ohms (magenta trace) and 2 ohms (red trace). The THD+N percentage doesn’t

rise at the top of the audioband, which suggests that the amplifier has commendably wide-bandwidth open-loop gain.

The distortion waveform was predominantly the third harmonic (fig.8), with no crossover distortion spikes at the waveform’s zero-crossing points. The third harmonic lies below –100dB (0.001%) into 8 ohms (fig.9) but rises to a still-low –84dB (0.006%) into 4 ohms (not shown). Even at a peak power of 100W into 4 ohms, the highorder intermodulation products with an equal mix of 19 and 20kHz tones all lay at or below –90dB (0.003%, fig.10). Commendably, the second-order difference product at 1kHz lay close to –120dB (0.0001%).

The Linn Klimax Solo 800’s measured performance is one of the best I have encountered, offering very high power with extremely low levels of noise and distortion. Wow!—John Atkinson

1 See stereophile.com/content/measurements-mapsprecision. 2 See stereophile.com/content/real-life-measurements-page-2. Fig.1 Linn Klimax Solo 800, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (blue), 4 ohms (magenta), and 2 ohms (red) (1dB/ vertical div.).

Fig.2 Linn Klimax Solo 800, small-signal 10kHz squarewave into 8 ohms.

Fig.3 Linn Klimax Solo 800, spectrum of 1kHz sinewave, DC–1kHz, at 1W into 8 ohms (linear frequency scale).

Fig.4 Linn Klimax Solo 800, distortion (%) vs 1kHz continuous output power into 8 ohms.

Fig.7 Linn Klimax Solo 800, THD+N (%) vs frequency at 20V into: 8 ohms (blue), 4 ohms (magenta), and 2 ohms (red).

Fig.5 Linn Klimax Solo 800, distortion (%) vs 1kHz continuous output power into 4 ohms.

Fig.6 Linn Klimax Solo 800, distortion (%) vs 1kHz continuous output power into 2 ohms.

Fig.8 Linn Klimax Solo 800, 1kHz waveform at 50W into 8 ohms, 0.0028% THD+N (top); distortion and noise waveform with fundamental notched out (bottom, not to scale).

Fig.10 Linn Klimax Solo 800, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 100W peak into 4 ohms (linear frequency scale).

Fig.9 Linn Klimax Solo 800, spectrum of 50Hz sinewave, DC–1kHz, at 50W into 8 ohms (linear frequency scale).