Perreaux R200i integrated amplifier Measurements

Sidebar 3: Measurements

My usual practice when measuring an amplifier is to precondition the device by running it with both channels driven at one-third power into 8 ohms for an hour. Though these conditions are unlikely to be met in real life (other than in the well-known "Party Test"), they maximize the thermal stress on the amplifier if it uses, as do 99.99% of amplifiers brought to market, an output stage biased to run in class-B or -A/B.

The Perreaux R200i's heatsinks got hot very quickly at this power level; the integral heatsink-temperature display showed that, from an idle temperature of around 40 degrees C, the sinks reached 77 degrees C (left) and 75 degrees C (right) after 15 minutes of preconditioning, and 82 degrees (L) and 83 degrees (R) after 30 minutes. At that point the R200i's microprocessor shut the amplifier down, its display indicating "Over Temperature." The entire chassis was extremely hot at this point, not just the side-mounted heatsinks.

While it is true that the R200i has inadequate heatsinking for this worst-case situation, as with other integrated amplifiers that have failed this test—for example, the Chord CPM-3300, reviewed by MF in July 2001—a better conclusion to draw is that the Perreaux's power rating is intended more to allow clipping-free reproduction of music than sustained high-power use. As long as that is understood, no harm, no foul. (One interesting point that emerged from this pre-test was that the THD+noise figure of 0.013% with the amplifier cold dropped to below 0.005% after 30 minutes.)

The maximum voltage gain with the R200i's volume control set to its maximum (an indicated "59") was 46.5dB for both the balanced and unbalanced inputs. The specification suggests that 30dB of this is due to the preamplifier section; I measured 17.7dB, which suggest the 30dB actually refers to the power amplifier section. Perhaps because of this high gain, the signal/noise ratios with the volume control at its maximum and the inputs short-circuited were a little disappointing: 59.2dB (unweighted wideband), 69.2dB (22Hz-22kHz), and 72.1dB (A-weighted), all figures ref. 1W into 8 ohms. But given that in typical use the volume control will be set to very much below its maximum, my disappointment is moot. The volume control operated throughout its range in 1.5dB steps—a little on the coarse side, in my experience, for setting exactly the right volume for every recording. Channel matching, however, was extremely good across the control's entire range.

The R200i preserved absolute polarity through all inputs, and its input impedance at 1kHz measured 9.8k ohms unbalanced, 15k ohms balanced. The output impedance of the power-amplifier section was superbly low—0.05 ohm—across most of the audioband, but this did rise to 0.185 ohm at 20kHz. The source impedance of the preamp output jacks was a usefully low 216.5 ohms. DC offsets at the speaker terminals were a moderate -9mV (L) and -12.4mV (R).

The small-signal frequency response with the volume control full (fig.1) was sensibly rolled off above the audioband, with the output into 8 ohms down by 0.25dB. The rolloff increased into lower impedances, however, that into 2 ohms being -0.8dB at 20kHz. As a result of this ultrasonic rolloff, a small-signal 10kHz squarewave showed some rounding of its leading edges (fig.2). Channel separation (fig.3) was very good in the L-R direction, at just below 100dB at 1kHz, but less so from R to L. The crosstalk in both directions increased at higher frequencies due to the usual capacitive coupling between the channels.

Fig.1 Perreaux R200i, line-input frequency response at (from top to bottom at 2kHz): 2.83V into simulated loudspeaker load, 1W into 8 ohms, 2W into 4 ohms, 4W into 2 ohms (0.5dB/vertical div., right channel dashed).

Fig.2 Perreaux R200i, small-signal 10kHz squarewave into 8 ohms.

Fig.3 Perreaux R200i, line-input channel separation (10dB/vertical div., R-L dashed).

The THD+noise percentage was very low, but, as can be seen from the plot against frequency into 8, 4, and 2 ohms (fig.4), was different from the two channels: the right channel was significantly better. Could this be associated with MF noting the different heatsink temperatures? I don't know. The distortion itself was heavily second-harmonic in nature (fig.5), which always correlates with good sound quality, though the Perreaux's absolute THD level is so low even at high output powers that I wouldn't have thought it would matter much.

Fig.4 Perreaux R200i, THD+N (%) vs frequency (from bottom to top at 40Hz): 15V into 8 ohms, 4 ohms, 2 ohms, and at 2.83V into simulated loudspeaker load.

Fig.5 Perreaux R200i, 1kHz waveform at 27W into 4 ohms (top), 0.016% THD+N; distortion and noise waveform with fundamental notched out (bottom, not to scale).

In fact, as can be seen from fig.6, which shows the spectrum of the R200i's output while it drove a 50Hz tone at 180W into 4 ohms, the highest-level spurious tone is at the power-supply-related frequency of 120Hz, this still at -86dB (0.005%) even at this high output level. (It dropped to -93dB, 0.0002%, when the load impedance was doubled to 8 ohms.) Intermodulation was similarly low in level, even with the amplifier about to clip into 4 ohms with the demanding high-frequency twin-tone signal (fig.7).

Fig.6 Perreaux R200i, spectrum of 50Hz sinewave, DC-1kHz, at 180W into 4 ohms (linear frequency scale).

Fig.7 Perreaux R200i, HF intermodulation spectrum, DC-24kHz, 19+20kHz at 205W into 4 ohms (linear frequency scale).

With both channels of the R200i driven with continuous tones, it more than exceeded its specified power into 8 ohms, with 268Wpc available (24.3dBW) at the point where the amplifier's display indicated "Over Current Left—Over Current Right," and it attenuated its output in a rather arbitrary manner (revealed by the wiggly trace at the bottom right of fig.8). No fewer than 402Wpc were available into 4 ohms at clipping (23dBW), but this time the R200i cut off cleanly, as it did into 2 ohms (fig.8, top trace). Just 197.4W were available into 2 ohms, however (16.9dBW), even with one channel driven.

Fig.8 Perreaux R200i, distortion (%) vs 1kHz continuous output power into (from bottom to top): 8 ohms, 4 ohms, 2 ohms.

Using the Perreaux R200i was a joy. Its remote-controllable menu and user interface are obviously well-thought-out and I was impressed by the amplifier's ability to protect itself without interfering with its operation below the stress points. However, the remote is so small and its buttons so close together that I kept hitting the wrong ones.

The R200i is not really recommendable for use with speakers that dip below 4 ohms for much of the audioband, or for sustained high-power use. But within those limits, it appears to be a well-engineered, overload-proof design. It comes as no surprise to find that MF liked how it sounded.—John Atkinson

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