PS Audio P300 Power Plant:
P-300 with MultiWave part 2
P-300 with MultiWave part 2 Goldberg then suggested another variant: adding a single odd harmonic to each sinewave fundamental to produce "partial" squarewaves, with flat tops that would allow capacitors in the power supply to be charged for a longer time (footnote 1). In the production version of the MultiWave board, the user can select either a pure sinewave (variable from 50Hz to 120Hz, as before), or one of nine MultiWaves that are sequences of sinewaves or partial squarewaves. For example, the SS1 setting has a 50Hz partial squarewave followed by two 120Hz partial squarewaves; SS4 is a 50Hz sinewave followed by two 120Hz sinewaves. PS2 is a single-frequency (60Hz) partial squarewave, and is recommended for equipment with cooling fans.

PS Audio's most highly recommended MultiWave patterns are those that have partial squarewaves, but PSA suggests that users experiment to find out which works best in their systems. The restrictions are that turntables that use AC motors must be used with pure sinewaves, and, as noted, equipment with fans should be used with the PS2 setting. The cost of the MultiWave option is $250, factory-installed or as an upgrade kit (board and new display). Installation is said to take only about 15 minutes.

Those Magic Changes
PS Audio provided a new sample of the P-300, with MultiWave installed, so that I could make A/B comparisons with my original non-MultiWave P-300. My first comparison was between the original P-300 set at the usual 80Hz and the new unit set at the same frequency. (Current-series Power Plants feature 81Hz rather than 80Hz because some owners use the Power Plant to change the speed of turntables with AC-synchronized motors; 81Hz produces exactly 45rpm.) The P-300 was used to provide the power to the PS Audio Lambda II transport, Bel Canto DAC1 or MSB LinkDAC III (upsampling card, P1000 power supply, Full Nelson upgrade) digital processor, and Convergent Audio Technology SL-1 Ultimate preamplifier. Speakers were Avantgarde Uno Series Twos, driven by a pair of Cary CAD-2A3 monoblock amplifiers.

If someone had asked me if I thought a drop in distortion from 0.05% to 0.025% would be significant, or even audible, my answer would have been an unequivocal "No!" Differences in amplifiers' residual distortions in this range are normally considered to be below the discrimination threshold, and claims of ultra-low distortion in amplifiers have been pointed out as examples of meaningless specsmanship.

Be that as it may, changing from my original P-300 to the new sample produced obvious sonic improvements. The entire upper-frequency range sounded cleaner, smoother, with more delicate extreme highs. The effect could be heard most easily on cymbals, which had a more airy, shimmery quality. (I noticed no difference in the bass.) If the P-300's MultiWave board did nothing more than this, the upgrade would be well worth it.

But this was all before switching from the pure sinewave to the MultiWave settings. Changing to the SS1 setting (which PS Audio highly recommends) resulted in a major improvement in dynamics, an opening up of the soundstage, greater depth, and an increased sense of power in the low bass. The change in bass performance was the sort that I would normally associate with a change in power amplifiers, but the CAD-2A3SE monoblocks and the Avantgarde Unos' subwoofer amplifiers were not even plugged into the P-300. (I tried to run the Carys from the P-300, but even though these amps produce only 5Wpc, they draw enough power that the P-300 shut down as soon as the second amplifier was turned on.) There was no apparent sonic downside to using the MultiWave setting: the highs were at least as clean and delicate as with sinewaves, and, unlike the case with sinewaves above 90Hz, there was no thinning of the midbass.

If SS1 had been the only MultiWave setting offered, I would have been content to stay with it—but there were eight more MultiWave settings to check out. I listened to them all—although, I must admit, not in the most extensive and systematic way—and SS5 emerged as my favorite. This MultiWave pattern is much like SS1, the difference being that SS1 is a partial squarewave sequence of 50/120/120Hz, whereas SS5 is a partial squarewave sequence of 60/120/120Hz.

My preference was based on two factors: the transformers in the digital processors plugged into the P-300 were quieter with SS5, and the bass was a bit cleaner with this setting (footnote 2). Another favorite reported by MultiWave users (there has been extensive discussion of this topic on the PS Audio website) is SS8, which consists of sinewaves of 60/120/120Hz. SS8 sounded pretty good, but in the end I returned to SS5.

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Footnote 1: The Power Plant technology, including the MultiWave story, is described in considerable detail at the PS Audio website.

Footnote 2: The displayed voltage readings with the P-300 set to MultiWave were significantly lower than the actual voltages measured with a voltmeter; eg, an indicated 117V measured as 122V. The discrepancy was confirmed by Paul McGowan, who said that this will be fixed in a software revision. To compensate for the voltage difference with the MultiWave settings, I lowered the voltage to an indicated 112V, which resulted in an actual 117V.