To pick the appropriate model, Plixir and bFly Audio use a basic rule of thumb: the BAC figure should exceed your actual power draw by at least 50%. The BAC 400 under review thus works ideally for up to 266 watts (266w x 1.5 = 400w) spread out over up to four components. By now the reader has matched model number to total power delivery. The 50% extra guarantees headroom for dynamic peaks. Realistically, the BAC 400 won't break a sweat even with a small amp like our Linn Majik DSM whilst leaving spare power for a record player or other 'easy' kit. Plixir appreciate that technically minded buyers love cryptic tekkie terms. Accordingly, our Asians call their balanced power isolation transformer a PureTone Sound Quality concept and promise the following gains:


Impedance conversion: Very low output impedance provides current without dynamic losses as long as the match between model and system conforms to their recommendation.
Isolation: Due to balanced power, harmonic powerline distortion is cancelled.
Optimized grounding: The scheme prevents ground loops and associated hum.


All of it comes from their toroidal isolation transformer which bFly Audio told me was developed in collaboration with Noratel, an expert at the top of this field. The transformer's specification makes for very narrow-band filtering at 50Hz. Within the domestic power delivery scope, anything not exactly of that frequency (or 60Hz for other countries) is dirt, hence potentially deleterious to the sound.


So the quiet heart of each Plixir AC conditioner is an isolation transformer to avoid the issues conventional line filters have with their capacitors and resistors. Plixir's James Soh views them as problematic. "Capacitors simply migrate the issue to ground or neutral and resistive methods involve dynamic restrictions. Often there's also a tonal balance shift from additional absorptive parts in the power path." An isolation transformer simply passes on utility power as determined by its frequency set by the precise ratio between primary and secondary. Power delivery is determined by transformer size, the filter effectiveness is set by winding geometry and quality. According to James Soh, "done properly, such filtering is very precise and effective."