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While the impedance of the output taps may be easily changed by going into the underside of the amplifier, this is not something we recommend a typical user do without dealer help. Table 1 Sonic Frontiers Power 2 Clipping (1% THD+noise at 1kHz) The Power 2's THD+noise vs output power curves are shown in fig.8, its discrete clipping in Table 1.įig.8 Sonic Frontiers Power 2, distortion (%) vs output power into (from bottom to top at 40W): 8 ohms, 4 ohms, and 2 ohms. The artifacts were slightly lower into 8 ohms, the single most prominent exception being –58dB (about 0.12%) at 1kHz (not shown).įig.6 Sonic Frontiers Power 2, 8 ohm tap, spectrum of 50Hz sinewave, DC–1kHz, at 74W into 4 ohms (linear frequency scale).įig.7 Sonic Frontiers Power 2, 8 ohm tap, HF intermodulation spectrum, DC–22kHz, 19+20kHz at 74W into 4 ohms (linear frequency scale).
![sonic frontiers power 2 sonic frontiers power 2](http://www.listeninn.com/Pictures-Used/Used-Power-Amplifier/Sonic-Frontiers-Power-2-6a.jpg)
The 1kHz intermodulation artifact is at –62.5dB (also about 0.075%) the distortion at 18kHz is –53.4dB (about 0.2%). The 19+20kHz IM spectrum at 74W into 4 ohms is plotted in fig.7. The largest artifact is the second harmonic, at –62.6dB (about 0.075%). The output spectrum resulting from a 50Hz input at 74W (2/3 rated power) into 4 ohms is shown in fig.6. The same is true with other loads (not shown), though signs of higher-order distortion products became more evident into our simulated load (if still at a low level).įig.5 Sonic Frontiers Power 2, 8 ohm tap, 1kHz waveform at 2W into 4 ohms (top) distortion and noise waveform with fundamental notched out (bottom, not to scale). The 1kHz THD+noise waveform at 2W out into 4 ohms (fig.5) is heavily second-harmonic. (The spikes were not visible in the balanced result, which was otherwise identical to the unbalanced and is not shown.)įig.4 Sonic Frontiers Power 2, 8 ohm tap, THD+noise vs frequency at (from top to bottom at 10kHz): 4W into 2 ohms, 2W into 4 ohms, 1W into 8 ohms, 2.83V into simulated speaker load (right channel dashed). The spikes visible in the left channel at 120Hz and 5kHz were repeatable and are likely noise-related, perhaps from a tube on its way out. THD+noise vs frequency is plotted in fig.4. The separation is high, with the typical decrease at higher frequencies due to capacitive coupling between the channels.įig.2 Sonic Frontiers Power 2, 8 ohm tap, small-signal 10kHz squarewave into 8 ohms.įig.3 Sonic Frontiers Power 2, crosstalk (from top to bottom at 20kHz): L–R, R–L (10dB/vertical div.). The latter is also just barely visible on the 1kHz squarewave (not shown). This is a fair to good result there is some visible overshoot, with just under two cycles of damped high-frequency ringing. The output of the Power 2 in response to a 10kHz squarewave is shown in fig.2. (The balanced frequency response, not shown, was virtually identical to the unbalanced.)įig.1 Sonic Frontiers Power 2, 8 ohm tap, frequency response at (from top to bottom at 5kHz): 1W into 8 ohms, 2W into 4 ohms, and 2.83V into simulated speaker load (right channel dashed, 0.5dB/vertical div.).
![sonic frontiers power 2 sonic frontiers power 2](http://www.listeninn.com/Pictures-Used/Used-Power-Amplifier/Sonic-Frontiers-Power-2-6b.jpg)
Note that, with our simulated real load, the deviations due to the amplifier's output impedance are relatively negligible, and the frequency response overall is more typical of a good solid-state design than of a tube amp.
![sonic frontiers power 2 sonic frontiers power 2](https://2img.net/h/i654.photobucket.com/albums/uu266/lonelong/power2no2.jpg)
This is a refreshingly low output impedance for a tube amplifier, suggesting a relatively consistent frequency response with varying loudspeaker loads.įig.1 shows the frequency response of the Power 2 at the conditions indicated. The output impedance of the Power 2 varied between 0.13 ohms and 0.17 ohms, the higher values occurring at 20kHz. The S/N ratio, unweighted (at 1W into 8 ohms), was 80.9dB over a 22Hz–22kHz bandwidth, 79dB from 10Hz to 500kHz (87.2dB, A-weighted). The Power 2 was noninverting, a positive-going input emerging positive at the output (pin 2 of the balanced input was wired as positive). DC offset was negligible at 0.4mV in the left channel, 0.5mV in the right. The input impedance measured 101k ohms (190k ohms balanced). Its voltage gain into 8 ohms measured 28.5dB, balanced or unbalanced. All measurements were taken with the amplifier configured for an 8 ohm output tap (see more on this at the end of this Sidebar).įollowing its preconditioning test, the Sonic Frontiers Power 2 was typically hot for a tube amplifier. The measurements of the Sonic Frontiers Power 2 were made in the unbalanced configuration, with selected readings taken in the balanced mode.
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