Australian HIFI - - CONTENTS - greg bor­row­man

There are many very ob­vi­ous rea­sons you might want to use a power con­di­tioner, but there are also some that are not quite so ob­vi­ous!

Idis­cov­ered a ma­jor fail­ing of the Torus AVR2 power con­di­tioner the mo­ment I tried to re­move it from the dou­ble card­board box in which it was de­liv­ered. It’s too heavy! Also, it does not have han­dles. A prod­uct that is this heavy (35kg) and this large (it mea­sures 430mm wide by 200mm high by 490mm deep) re­ally needs to be pro­vided with han­dles—two as a min­i­mum, and prefer­ably four, so it be­comes an easy two-per­son lift.

I guess the only god­send was that I wasn’t re­view­ing the 20-amp ver­sion of the Torus AVR2, which is even big­ger and, at 74kg, more than twice the weight!


The Torus AVR2 (the AVR stands for Au­to­matic Volt­age Reg­u­la­tor) is a power con­di­tioner that re­moves volt­age spikes and high-fre­quency noise from the mains power sup­ply be­fore they can get to the com­po­nents in your hi-fi sys­tem. It also sta­bilises the mains volt­age so there are fewer fluc­tu­a­tions, and keeps that volt­age to within ±10 volts here in Aus­tralia, with our nom­i­nally 240V sup­ply. (In the US and other coun­tries us­ing a 120V sup­ply, the Torus AVR2 keeps the nom­i­nal volt­age to within ±5 volts). This pre­vents against volt­age surges and brownouts. How­ever, in the event that the mains volt­age ex­ceeds 262 volts, or falls be­low 170 volts, the Torus AVR2 will au­to­mat­i­cally dis­con­nect your hi-fi com­po­nents from the mains power sup­ply to pro­tect them.

Once you have wres­tled the Torus AVR2 out of the box and placed it on your equip­ment rack—or the floor—it’s sim­ply a mat­ter of plug­ging your hi-fi com­po­nents into the five empty 240V ‘med­i­cal grade’ mains sock­ets on the rear, plug­ging the Torus AVR2 into a stan­dard 15-amp wall socket and switch­ing it on.

The minute you switch the Torus AVR2 on, the small dis­play at the right of the front panel will light up, with the top line show­ing the in­com­ing volt­age and the bot­tom line the out­go­ing volt­age. I was a bit alarmed when I first turned mine on, be­cause it showed an in­com­ing of 242 volts and an out­go­ing of 270-volts. I rapidly switched if off, fear­ing some­thing had gone wrong.

A care­ful read­ing of the man­ual showed that I needn’t have wor­ried, be­cause the out­put volt­age shown on the front panel is not ac­tu­ally con­nected to the sock­ets at the rear un­til af­ter the Torus AVR2 has sta­bilised the volt­age, us­ing a series of re­lays, and this process can take up to 20 sec­onds. So I switched on again, and watched the out­put volt­age slowly drop from 270 volts to 238 volts, af­ter which that ex­act volt­age was ap­plied to the rear 240V out­lets prior to switch-on.

The Torus AVR2’s front panel dis­play shows not only the level of the in­put and out­put volt­ages, it also shows to­tal cur­rent be­ing drawn by your sys­tem (in amps) on the same dis­play. If you push the but­ton be­low the dis­play, it will then show both av­er­age and peak power. Push it again and it will show the time and date. Press it once more and it will show the power out­lets on the rear that are draw­ing power. For some rea­son these are called ‘ac­tive zones.’ Press the but­ton once more and the dis­play will show the IP ad­dress of your Torus AVR2 (only if you’ve con­nected it to the in­ter­net).

As you have prob­a­bly guessed by that paren­the­sised com­ment, you can con­nect the Torus AVR2 to the in­ter­net, us­ing the Eth­er­net port pro­vided on the rear. If you do this, a whole new raft of fea­tures ap­pears.

Once your com­puter is con­nected to the Torus AVR2, you can check its sta­tus from any­where in the world, as well as op­er­ate it from any­where in the world. And, once a com­puter is con­nected, you can in­di­vid­u­ally switch the rear power sock­ets on or off. You can do this switch­ing man­u­ally, or you can pro­gram them to turn on and off at spe­cific times, on spe­cific days of the week. You can also pro­gram the Torus AVR2 to send you an email if the AVRs ex­pe­ri­ences what the in­struc­tion man­ual calls ‘an is­sue’, in which case it will send you an email notification of the spe­cific fault con­di­tion that took place.

Al­though these ca­pa­bil­i­ties are im­pres­sive, I won­dered why all this func­tion­al­ity had been pro­vided. If I am on the other side of the world, why would I want to be able to switch my sys­tem on or off, or have it do so in my ab­sence? Whilst pon­der­ing this, I dis­cov­ered that when­ever the Torus AVR2 switches on, it switches on each power out­let (aka ‘zone’) in or­der, start­ing with A. This is re­ally use­ful, be­cause it means you can con­nect (say) a disc or net­work player to A, your pream­pli­fier to B and each of your mono power am­pli­fiers to C and D. This will cor­rectly se­quence your sys­tem power-up pat­tern to pre­vent po­ten­tially dam­ag­ing turn-on tran­sients from reach­ing your loud­speak­ers. How­ever, I have to note that this won’t be so use­ful if the com­po­nents in your sys­tem switch to standby power when they’re not be­ing used.

Later on I also found that with your com­puter con­nected you can ac­tu­ally cal­i­brate the Torus AVR2, but since this process nec­es­sar­ily in­volves us­ing a cal­i­brated volt­meter and the op­er­a­tor of that volt­meter po­ten­tially be­ing ex­posed to lethal volt­ages whilst mea­sur­ing, this process is not in­cluded in the oth­er­wise to­tally com­pre­hen­sive and un­nec­es­sar­ily lengthy Own­ers’ Man­ual.

In Use and LIs­ten­Ing ses­sIons

There are many very ob­vi­ous rea­sons you might want to use a power con­di­tioner. First would be to sta­bilise the mains volt­age reach­ing your com­po­nents be­cause there’s a pos­si­bil­ity that surges and low-volt­ages could do them some harm. It is, how­ever, only a pos­si­bil­ity, as most com­po­nents are built to cope with surges and low-volt­ages.

An­other rea­son for us­ing a power con­di­tioner would be to eliminate high-fre­quency noise spikes from the mains power, as these can ad­versely af­fect the op­er­a­tion of dig­i­tal-to-ana­logue con­vert­ers, for ex­am­ple… though, once again, most com­po­nents that could be sen­si­tive to noise on the power line are de­signed to re­move that noise them­selves, to en­sure proper performance.

How­ever there is one not-so-ob­vi­ous rea­son for us­ing a mains power con­di­tioner, which is to re­move au­di­ble trans­former hum from your com­po­nents.

Trans­former hum used to be quite an is­sue in the past, par­tic­u­larly here in Aus­tralia, be­cause most trans­form­ers were made by lam­i­nat­ing plates to­gether and winding coils around those plates. The prob­lem was that most trans­form­ers were de­signed for op­er­a­tion at a mains fre­quency of 60Hz and a mains volt­age of 120V. Here in Aus­tralia, when those same trans­form­ers (with dif­fer­ent taps to ac­com­mo­date the in­creased volt­age) were used, the higher volt­age com­bined with the lower mains fre­quency (50Hz) caused the lam­i­nated plates to vi­brate, caus­ing an au­di­ble hum at 50Hz. In some cases the trans­former vi­brated so much that it ac­tu­ally caused a buzzing sound.

It was largely be­cause of this hum prob­lem that most equip­ment man­u­fac­tur­ers have switched over to us­ing toroidal mains power trans­form­ers, which are not made by lam­i­nat­ing plates to­gether. Which is not to say they made the switch to toroidals sim­ply to solve this is­sue…toroidal trans­form­ers have many tech­ni­cal ad­van­tages over stan­dard trans­form­ers, plus a smaller form fac­tor, so us­ing them also al­lowed man­u­fac­tur­ers to cut costs in many cases.

How­ever, al­though toroidal trans­form­ers are in­trin­si­cally acous­ti­cally quiet (very lit­tle hum) when fed from an ideal 240V source, they can be­come noisy un­der ad­verse line con­di­tions, which will re­sult in the com­po­nents they’re be­ing used in gen­er­at­ing au­di­ble hum in the lis­ten­ing room… usu­ally at 50Hz, but some­times also at 100Hz and 150Hz. If your com­po­nents pro­duce an au­di­ble hum when they’re oper­at­ing as a re­sult of sub-stan­dard mains power, us­ing a power con­di­tioner should re­duce or eliminate it. One com­pli­ca­tion with as­sess­ing au­di­ble hum is that the level of hum will vary de­pend­ing on the mu­sic be­ing played, and the vol­ume at which it is be­ing played, be­cause hum lev­els will al­ways be higher when a trans­former is be­ing stressed than when it’s just idling along.

An­other rea­son you might want to use a power con­di­tioner is if you’re run­ning a high-power am­pli­fier. In many cases, de­pend­ing on the sup­ply volt­age in your area, if your am­pli­fier is run­ning flat out, it could be pulling so much cur­rent from the mains that the mains volt­age will drop, re­sult­ing in re­duced am­pli­fier performance. A power con­di­tioner such as the Torus AVR2 will main­tain the cor­rect sup­ply volt­age even un­der con­di­tions of peak de­mand.

Yet an­other rea­son is ground loops. If your mains con­nec­tions are such that there are mul­ti­ple paths for elec­tric­ity to flow to ground they may form a ‘loop’ which may then pick up stray cur­rent via means of elec­tro­mag­netic in­duc­tion, re­sult­ing in un­wanted cur­rent in a con­duc­tor that’s con­nect­ing two points that are sup­posed to be at the same po­ten­tial. The re­sult of a gound loop is hum. With all your com­po­nents plugged into the AV2, all the earths will be at ex­actly the same po­ten­tial, elim­i­nat­ing the pos­si­bil­ity of hum-gen­er­at­ing ground loops.

In Use and Performance

I thought I’d check the Torus AVR2’s volt­age con­trol abil­ity be­fore I com­menced my re­view, so I con­nected it to a vari­able mains power trans­former (Variac) I use when I am re­view­ing 120-volt prod­ucts, as it al­lows me to ad­just mains volt­age from 110 volts up to 270 volts. I first set the Variac at 230 volts, be­cause this is the volt­age the mains is sup­posed to be here in Aus­tralia. I say sup­posed be­cause al­though the Australian gov­ern­ment com­mit­ted to switch­ing from 240 volts down to 230 volts to har­monise with the Euro­pean mains volt­age sev­eral years ago, it has never hap­pened. Or, per­haps, it has hap­pened in some re­gions and with some sup­pli­ers, but not in oth­ers… and cer­tainly not in my sub­urb. Any­way, with the Variac set at 230 volts, the Torus AVR2 put out a con­stant 235 volts. This seemed a lit­tle strange, and af­ter a few emails with the Australian dis­trib­u­tor, it tran­spired that the op­er­a­tion of the Torus AVR2 is some­what de­pen­dent on the load that’s con­nected to it, and for my ini­tial tests I’d con­nected a load that was draw­ing only 0.1-amps. When I in­creased the load to 2.8amps, the volt­age dropped back to 230 volts, right on the money.

With the big­ger load con­nected I ramped up the Variac to 234 volts, for which the AVR de­liv­ered 237 volts. I then wound the Variac

right up to 240 volts, at which there was a click from within the Torus AVR2 and the volt­age dropped back to 233 volts. I then in­creased the mains volt­age again, from 240 volts through to 258 volts, and watched the out­put volt­age of the Torus AVR2 climb from 233 volts to 240 volts. With an in­put volt­age of 260 volts, the Torus AVR2 put out 243 volts, slightly above its ±10V rat­ing, but pre­sum­ably if I had in­creased the load, it would have dropped it down to 240 volts. At 262-volts, the AVR dis­con­nected all the loads con­nected to it, and dis­played ‘High Volt­age’.

When I re­duced the volt­age to 226 volts, the Torus AVR2’s out­put volt­age dropped to 229 volts, and for an in­put volt­age of 224 volts its out­put volt­age dropped to 226 volts and so on, de­liv­er­ing ever-re­duc­ing volt­age un­til it was de­liv­er­ing a 220 volt out­put for a 218 volt in­put. Then, when I re­duced in­put volt­age to 216 volts, a re­lay clicked and the Torus AVR2’s out­put went back up to 227 volts. When I got all the way down to an in­put volt­age of 170 volts, the Torus AVR2 again dis­con­nected the com­po­nents con­nected to it, but this time dis­played the words ‘Low Volt­age’ in the front panel dis­play.

So over­all, my tests showed that with the load I used for the tests the Torus AV2 will main­tain an out­put volt­age of be­tween 220 volts and 240 volts for any in­put volt­age be­tween 172 and 258 volts. The re­sults of my tests are shown in the ac­com­pa­ny­ing graph.

My first sonic trial with the Torus AVR2 was with an 80s vin­tage am­pli­fier I keep for sen­ti­men­tal rea­sons (don’t ask, or you’ll be like my wife, who’s al­ways ask­ing me why I don’t get rid of it!). It has a toroidal trans­former that hums so loudly I could hear it from the lis­ten­ing po­si­tion (just one of the rea­sons I no longer use it). Af­ter tak­ing it down from its usual rest­ing place on the top shelf of my home of­fice I was a bit sur­prised to find the amp even worked, as it hadn’t been switched on for some­thing ap­proach­ing 15 years, but when I plugged it in, away it went, and it cer­tainly hadn’t for­got­ten how to hum…. at least it hadn’t when it was plugged di­rectly into the mains power socket on the wall. How­ever, when I con­nected it to the Torus AVR2’s out­put, the hum all but van­ished… at least I could no longer hear it from my lis­ten­ing po­si­tion—though I could still hear some hum if I put my ear close enough to the am­pli­fier’s case.

Some­what sur­prised by this out­come, I tried an­other am­pli­fier which uses a stan­dard EI trans­former, not a toroid, but from which a slight hum has al­ways been au­di­ble if I put my ear right up against the case. When it was con­nected via the Torus AVR2, the trans­former hum was still present, but to my ear it was at a dis­tinctly lower vol­ume level.

My third sonic trial was sim­ply to hear whether the Torus AVR2 had any ef­fect on am­pli­fier sound quality, us­ing two dif­fer­ent but iden­ti­cal hi-fi sys­tems, but with one sys­tem con­nected di­rectly to a mains wall socket and the other to the Torus AVR2. In the set-up I used, both sys­tems did share a com­mon source com­po­nent (an SACD player), in or­der to sim­plify the A–B switch­ing process. In these ses­sions, dur­ing which the volt­age of the wall socket re­mained fairly con­stant at around 242–244 volts (and the out­put volt­age of the Torus AVR2 also re­mained fairly con­stant, but at 234–237 volts) I found it ex­tremely dif­fi­cult to tell the two au­dio sys­tems apart, such that I fan­cied the dif­fer­ences I heard could equally be due to the nec­es­sar­ily dif­fer­ent lo­ca­tions of the speakers in the room. Which is not to say that I didn’t have quite a few ‘aha!’ mo­ments, when I def­i­nitely thought I’d found a mu­si­cal pas­sage where I thought the sound from the sys­tem con­nected via the Torus AVR2 sounded clearly bet­ter, but when I then re­played that pas­sage mul­ti­ple times through both sys­tems, I again found it hard to hear the difference I first heard. This hap­pened quite a few times, as I said: in­deed so of­ten that I be­gan to won­der whether it was be­cause of tran­sient noise spikes on the mains that ex­isted for a short pe­riod and had been re­moved by the Torus AVR2, but had dis­si­pated by the time I went back to do my dou­ble-checks. Un­for­tu­nately, I have no way of know­ing.My last ex­per­i­ment with the Torus AVR2 was to in­ten­tion­ally re­duce the mains volt­ages to both sys­tems to just 217 volts, so that one sys­tem was get­ting a true 217 volts, but the other one (thanks to the Torus AVR2 au­to­mat­i­cally boost­ing the volt­age to it) was get­ting around 230 volts. In this last ex­per­i­ment I clearly heard that the sound of the sys­tem con­nected to the Torus AVR2 was su­pe­rior, par­tic­u­larly dur­ing tran­sients, where the sound was cleaner, more dy­namic, and with less dis­tor­tion.


The ef­fect of ad­ding a power con­di­tioner to a hi-fi sys­tem will vary appe­cia­bly de­pend­ing on the quality of the mains power be­ing sup­plied to that sys­tem in the first place, the sup­ply volt­age it­self, and the de­sign of the power sup­plies in the com­po­nents in that sys­tem.

For ex­am­ple, if you’re lucky enough to be liv­ing in a house that is sup­plied with clean, sta­ble mains power at the cor­rect volt­age, and the power sup­plies in the com­po­nents in your sys­tem al­ready have their own fil­ter­ing and volt­age reg­u­la­tion cir­cuitry built in, I think it would be un­likely that you would ob­tain any au­di­ble ben­e­fit from ad­ding a power con­di­tioner.

If, on the other hand, you live in a home that has a less-than-per­fect mains sup­ply and/ or the com­po­nents in your sys­tem have lit­tle in the way of fil­ter­ing and volt­age reg­u­la­tion— or none—then us­ing a power con­di­tioner could cer­tainly pro­vide tan­gi­ble ben­e­fits.

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