Inouye Synergistic Power Line Conditioner

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[adapted from March 1989 Stereophile review]

Dual power line conditioner with: 1800VA capacity; two independent sets of two output sockets, transient protection fuses, and limited five-year warranty. Price: $525 [1989]. Approximate number of dealers: 20. Distributor: Artech Electronics Ltd., P.O. Box 1165, Champlain, NY 12919. Tel: (514) 631-6448.

If you ever have the need to separate those at the cutting edge of audiophilia nervosa from the skeptics/conservatives of the audio world, all you need do is ask whether the quality of the mains voltage available from the wall socket has any effect on a system’s sound quality. “Absolutely not,” the latter group would guffaw pointing out to their questioner that between the line cord of any component and its audio circuitry is a hefty filtering system, consisting of the mains transformer, one or more diode bridges, and shunt arrays of electrolytic reservoir capacitors, often bypassed with low-value film caps to ensure a low impedance at RE Any high-frequency noise on the line will be faced with a very-low impedance pathway to ground.

In addition, most modern hi-fi components— the exception being the output stages of nearly all power amplifiers—interpose some kind of voltage regulation between the basic power supply and the audio stages, this offering per haps another 50—60dB of audio-band power- supply noise rejection. In fact, it is usual in circuit analysis, I understand, to assume that all power-supply rails, no matter what their DC voltage are at ground potential with respect to AC signals, so low is the power-supply impedance to ground assumed to be. Even if there is a significant degree of HF noise on the AC line, it will be efficiently shunted to ground long before it can have any effect on a component’s sound quality.

And as nearly all modern electronic components are dual-rail, complementary designs, any noise which is identical on both live and neutral lines, even if it did manage to get through to the sensitive audio sections, will be rejected by those circuits’ intrinsic common- mode rejection.

Yet many audiophiles, having experimented with the various power-line filters and transient spike suppressors available for use with computers, report hearing sonic improvements with some of these theoretically superfluous devices. In Stereophile Vol.11 No.4, Lewis Lipnick found that Adcom’s ACE-515 RF filter/spike suppressor unit improved the performance of a pair of Rowland Research Model Five power amplifiers, improving the sense of focus and clarity, as well as improving the sense of solidity in the bass (though the same manufacturer’s Coherence One preamplifier seemed unaffected, and the Model Seven power amplifier was made to sound watery and thin). On the other hand, Lewis didn’t like the effect of the Straight Wire Power Purifier 8, a much more sophisticated unit that is said to ensure that the mains waveform is a good sinewave. Even though LL found that it reduced the levels of midrange background noise, he felt that it limited dynamics, endowing the music with an overall gray coloration.

[1. I’m talking here specifically of units that employ simple filtering and transient suppression. Conditioners that employ some kind of ferroresonant circuit, as supplied for use with computers, are a complete no-no foe hi-fi purposes in my opinion. Even if you can stand the mechanical hum, I believe they impose a high source impedance on the AC mains, which is the last thing you would want for an amplifier or preamplifier.]

The Inouye Synergistic Power Line Conditioner appears to be similar to the Adcom product in that it offers filtration of RFI and noise. It is built on an aluminum, nonmagnetic chassis, and fitted with a large-gauge power cord. Internally, the line-conditioner circuitry is contained on a single, large, double-sided printed circuit board. Following the wall power as it enters the conditioner through a standard IEC socket, the Live voltage goes via a thick pcb track to first a 15A circuit-breaker, then to the on/off switch, this containing a red neon indicator lamp. Both the Live and Neutral rails are shunted to ground by high-voltage ceramic capacitors (to provide a low-impedance ground for RF noise) and by metal-oxide varistors (to squelch transient voltage peaks higher than the mains’s maximum 170V or so). Both Live and Neutral lines are divided into two at this point, each feeding two sets of two three-pin sockets via an elaborate filtering arrangement of two heavy-gauge, air-cored coils per line, giving a total of eight, and eight more ceramic capacitors. These components appear to make up series L-C-L filters. A star-grounding topology is used, again via thick pcb traces. Finally, each pair of sockets is further protected against transient spikes with a series fuse/shunt vans ton/red neon/shunt varistor/series fuse net work. The neons remain lit while this final transient defense is active.

A small criticism concerning these four internal fuses, which presumably will have to be replaced occasionally: The cover is fixed to the chassis with Allen-head screws, and one screw on the review sample was fastened so tight that I stripped its hexagonal socket with the wrench. I had to drill the screw out to remove the cover, which was a pain in the neck. Perhaps Inouye could look into this problem.

One of the factors that bothers me with any type of line conditioner is that long experience has led me to distrust anything that places any kind of impedance upstream of a hi-fi component’s power supply Arnie Balgalvis has reported in these pages the favorable effects of having a dedicated AC circuit installed directly between the house circuit-breaker and his hi-fi system; I plan to have a dedicated supply installed for my relatively new listening room later this Spring. I am extremely distrustful of having anything in the line that would impede, for example, a power amplifier’s need to suck cur rent from the pole transformer. The traditional “Christmas Tree” of two- and three-way mains adaptors plugged into a single socket is anathema, therefore. Inouye, however, claims a very low insertion loss for their SPLC: I measured a presumably negligible in/Out impedance of approximately 0.75 ohms on each rail at 60Hz. While the conditioner would pass audio-band energy present on the line, it shunted components higher than 20kHz to ground with increasing effectiveness as the frequency increased. Looking (carefully) at the AC wave form straight from the wall with a ‘scope, I could induce HF noise on the line with thyristor dimmer switches and add some triangulation by turning on and off my trusty Black & Decker drill plugged into the same circuit. Looking at the output of the Inouye SPLC, the sinewave remained slightly more pure with the drill operating, though it still was triangulated a little at the moment when the drill was turned on. It was also hard to come to any sensible conclusion regarding the HF thyristor switching noise as the Inouye appeared to have no effect.

I suspect that the short length of unscreened twin cable between the Conditioner and a voltage divider/current limiter at the ‘scope input was picking up RF noise radiated from the dimmer.

The main problem here seemed to be that the mains waveform in Stereophile’s part of New Mexico is a very good sinewave—due to a low population density and a complete lack of heavy industry Given that moving to New Jersey for this review is Out of the question, something else was called for to reveal the SPLC’s intrinsic behavior. Feeding a high- frequency sinewave into the Inouye’s mains input, between either leg to ground, revealed a deep notch to appear at 88kHz—presumably the fundamental tuning of the filter—when the response at the appropriate conditioned output was measured. Measuring the series impedance of the neutral leg and its impedance to ground at spot frequencies also indicated that the unit’s response should roll off above the audio band, but in addition indicated that another notch should be present at 44kHz—except that I couldn’t then find this notch with a high-frequency sinewave sweep. (A puzzle!)

Could it be significant that these notches coincide with the fundamental CD sampling frequency and its second harmonic present to some extent in the outputs of all CD players? I haven’t the faintest idea, except that with the CD players and digital processors I had to hand—the Sony DAS-R1, Accuphase DP-80L/ DC-81L, Precision Audio DVIC-471, Magnavox CDB472, and Theta DS Pre—I rapidly became convinced that there was a significant, if vari able, degree of improvement in their sound. In general, it was as though the black of the sonic backgrounds became even more black, to the benefit of the music, with an opening up of the back of the soundstage. The greatest effect noticeable was with the least expensive player.

Am I reporting on the sound of CD players with less noise on their AC mains inputs? I don’t actually think so. Of course, you can’t listen to a CD player that doesn’t have a headphone socket without a power amplifier or speaker, so identifying cause and effect is impossible. But I am sure that the audible improvement here is not so much the reduction of mains-borne noise that would otherwise degrade CD- player performance, but the other way around: when a CD player is plugged into the Inouye filter, RF garbage present on its power supply rails (which, if not shunted to ground by the reservoir electrolytics, will find its way to the mains supply via the diode bridge the “wrong” way around) is prevented from affecting the performance of the preamplifier and power amplifier. Here the two sets of sockets on the Inouye start to make sense: plug the CD player into one, then use the other for the preamplifier.

[2. Under no circumstances should the SPLCs cover be removed while the unit is plugged into the wall. The entire pcb is at mains potential!]

My next auditioning session involved trying the conditioner with my Linn Sondek LP12 plugged into it. The Linn has a frequency-synthesized supply to provide its synchronous motor with a 60Hz AC sinewave, so any noise present on the AC line should be expected to have no effect. In addition, as with any belt- driven turntable, the flexible belt acts as a low- pass filter in conjunction with the moment of inertia of the rotating platter, rejecting any HF fluctuations in the motion of the motor. Things weren’t so cut and dried, however, when it came to the listening. Half the time I felt that the SPLC rendered the music more stable in its pitch centers; half the time I didn’t. No conclusion here, I’m afraid.

Inouye suggests that electrostatic loudspeakers benefit from having their polarizing supplies plugged into the SPLC, with users in Canada reporting a 30—50% improvement in performance. I intend, therefore, to pass the review sample on to Dick Olsher or J. Gordon Holt so that they can report on its effect with Quads and Sound Labs, respectively.

Returning to electronics, I don’t use a conventional preamplifier at present in my reference system: the Mod Squad’s Line Drive Deluxe AGT forms the system heart, with the Vendetta Research SCP2 dual-mono phono preamplifier providing the urge and equalization for LP replay. I tried the effect of the SPLC on the sound of the Vendetta Research. Well, the results were not as favorable as with the CD players. With a phono preamplifier plugged into each channel of the Inouye, the sound became somewhat less full-blooded, with less of a feeling of unrestricted low-frequency dynamics. This effect was, to my surprise, not noticeable when I tried the Inouye conditioner with the VTL 100W monos—one plugged into each half of the SPLC—but was a factor with my Krell KSA-50. The sound of the VTLs seemed to improve, however, becoming more fluid. The rather forward midrange characteristic of this amplifier receded, the soundstage thus acquiring a touch more depth. Low frequencies did acquire a touch more bloom, though this was not enough for the bass to sound more under-damped. To be honest, though, this effect on the VTLs’ bass was almost insignificant much of the time.

To explore the effect of the Inouye with a more conventional preamplifier, I then used it with the line stage of a PS Audio 4.6 fitted with its M-500 power supply. (As this was at night, I had the dimmer-controlled lights on— might as well give the SPLC something to get its teeth into.) After my experience with power amplifiers, I wasn’t expecting much of a change with the Inouye SPLC. The 4.6’s auxiliary power transformer is a massive hunk of iron ware that you would not expect to benefit from any additional AC line filtration, particularly with the relatively clean AC here in Santa Fe. I was very wrong. The difference between the 4.6 sans the Inouye and with it upstream of the preamp supply was the largest I experienced with any of the equipment I had to hand. The sound of the 4.6 line stage is something I always think of as “typical” PS: open, clear, detailed, always musical, but also grainy in the lower treble when compared with true Class A preamps. This is why I prefer to use it in its “straight-wire” setting, when it acts as a passive control center. Yet listening to Tracy Chapman (Elektra 960774-1),3 with the 4.6’s line stage in circuit, the Inouye rendered the sound considerably more musical. The lower-treble graininess, heard as a “cack” in Chapman’s mocha-flavored vocalizing, was considerably reduced, the sound becoming smoother yet without mellowing Out HF detail. The triangle on “Mountains of Things,” for instance, remained as clear as crystal. Not surprisingly, Tracy Chapman led to Joan Armatrading: the superb “ Willow” from her 1977 Show Some Emotion. Again, the effect of the SPLC was to render the singer less electronic, the music more accessible, and now a suspicion I had about the low frequencies was confirmed. Kick drum had more body, more “thud”; bass guitar had more weight.

I also used the Inouye SPLC with my dedicated headphone amplifier for most of the head phone listening to be reported on in the next issue. Here, again, I found the effect to be an improvement. Backgrounds became a deeper grade of silent, and instrumental specificity within the soundstage improved. Any hint of aggressiveness in the treble was diminished. To put these comments into context, the improvement was remarkably similar to that observed between the sound of an amplifier or preamplifier when it is first turned on and that when it is fully warmed-up.

[3. It is one of the tragedies of hi-fi shows that they enable you to hear great albums like this too many times. My colleague at Gramophone, Ivor Humphreys, feels that much contemporary music has the equivalent of a sell-by date after a certain number of plays, you do not need to hear the music again.Unfortunately; the musically monotonous overkill at this year’s WCES almost got me to that stage with this album.]


To sum up my findings: The Inouye Synergistic Power Line Conditioner had positive effects on the system’s sonics when CD players were plugged into it; it had, as best as I can conclude no effect on the Linn Sondek (though it might offer an improvement with turntables driven directly from the mains voltage, particularly in areas where the mains is particularly dirty); it changed the sound of the Vendetta Research phono preamplifier and the Krell KSA-50 in ways that I felt to be worse; it changed the sound of the VTL monoblocks and of my class-A headphone amplifier in ways which I felt to be improvements; and it effected an astonishing improvement on the sound of the PS Audio 4.6/M-500 combination’s line stage. (Any improvement from its use with electrostatic speakers is still to be reported on.) As Larry Archibald offered when I discussed this review’s findings with him, “it appears the better a component’s power supply, the smaller the degree of improvement offered by the Inouye,” which I suppose is pretty obvious when you think about it, as is “the better the quality of your mains and the cleanliness of your RF environment, the less need you have for such a device.” Except that this neat theorizing doesn’t jibe with my experience of the PS Audio preamplifier We1l-made and certainly offering very positive effects with some of the equipment with which I used it, the $525 Inouye faces stiff competition from Adcom’s ACE-515 ($180), from The Audio Advisor’s Tripplite LC- 1800 ($308), and even from Straight Wire’s Power Purifier 8 ($495). Stereophile received a significant amount of strongly dissenting mail from readers following the appearance of Lewis’s mainly negative review last April (for example, see the letter from Mr. William Beuthel of Denver, CO, in Vol.11 No.11, p.27). As the SPLC’s effect will be component-dependent and will also depend on the degree to which your AC mains is noisy or contaminated, I suggest that, if you can find a dealer willing to cooperate, you try the Inouye with each of your components in your own system before making a final purchase decision. You may find that you get the same improvement with your preamplifier that I did with the 4.6. As for me, the Inouye’s effect on CD replay in my reference system was sufficiently great that I wouldn’t want to part with it.

[4. Someone living in the heart of a city, with a large variety of thyristor dimmers, TVs with switched power supplies, and electric motors of all kinds, will be in a situation very different from someone who lives in the remote depths of one of the mountain states.]

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Also see: -- Inouye

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Updated: Wednesday, 2015-05-13 21:21 PST