HIGH-END RE­VIEW

AM­PLI­FIER

Australian HIFI - - CONTENTS -

Af­ter eight years, Dan­ish de­signer Hans Ole Vi­tus has made changes to his RI-100 in­te­grated am­pli­fier and re-named it the RI-101. Its op­tional DAC mod­ule uses ESS Tech­nolo­gies’ most ex­pen­sive IC.

Eight years is a long time in the high-end au­dio busi­ness. But that’s how long Vi­tus Au­dio had its RI-100 in­te­grated in its am­pli­fier line-up, so you’d have to as­sume that the com­pany’s founder and head de­signer Hans Ole Vi­tus was so happy with it that he didn’t see any need for an up­date… un­til now, that is, since he’s re­placed it with the RI-101.

Not that you’d know he’d re­placed the RI-100 just by look­ing at the new RI-101, how­ever, be­cause it ap­pears he’s us­ing an iden­ti­cal chas­sis. In­deed, if you had X-ray vi­sion and could look in­side the chas­sis it­self, it even ap­pears as though he’s us­ing the same printed cir­cuit boards. And ac­tu­ally, he is do­ing that… at least for the power am­pli­fier sec­tion of the RI-101. When asked via email about the many sim­i­lar­i­ties be­tween the old and new model, Vi­tus replied: ‘ The over­all de­sign of the RI-101 is the same as the orig­i­nal RI-100, so the main power sup­ply is iden­ti­cal, the out­put stage ditto. But that’s where the sim­i­lar­ity stops. Ev­ery­thing around the in­put stage in the power am­pli­fier sec­tion is new, and sig­nif­i­cantly up­dated. Even though this does not show di­rectly when com­par­ing the boards, there are many dif­fer­ences.’

the equip­ment

As with the RI-100, the RI-101 is avail­able in mul­ti­ple fin­ishes. My re­view model had a brushed alu­minium front panel, with brushed alu­minium push­but­tons and the front panel writ­ing was en­graved into that alu­minium, with no fill colour. This gave the am­pli­fier an in­cred­i­bly clean and stylish fin­ish but made it rather hard to read what each con­trol does. You can ap­par­ently op­tion­ally have the en­graved let­ter­ing ‘blacked-in’ to make it eas­ier to read. You can also or­der black but­tons, rather than brushed alu­minium ones. You can also or­der the RI-101 in black or gold… or, in­deed in any gloss paint colour. I have in­cluded some pho­tographs sup­plied by Vi­tus Au­dio to give you an idea of what’s pos­si­ble… but I sus­pect some of these im­ages are ac­tu­ally of an older RI-100, not the newer RI-10—as I said, you can’t tell the dif­fer­ence.

It’s also pos­si­ble to op­tion an in­built DAC with the RI-101. There were two cut-outs on the rear panel of my re­view model la­belled ‘Op­tional DAC Mod­ule’. If you op­tion in this DAC, the left-most of these will con­tain LAN and USB (B) sock­ets, and the right­most cutout will have AES and S/PDIF sock­ets. Op­tion­ing-in this DAC will cost you an ad­di­tional $5,990. Ini­tially—and be­cause In­put 5 of my re­view sam­ple was marked ‘In­put 5/RIAA’—I thought that it was also pos­si­ble to or­der the RI-101 with a built-in phono pream­pli­fier, as was the case with the orig­i­nal RI100.

How­ever, when an en­quiry was made of the Aus­tralian dis­trib­u­tor, Ab­so­lute Hi End, about the cost of do­ing this, the an­swer came back that: ‘No, it is not pos­si­ble to fit a phono stage to the RI-101.’ This be­ing the case, Vi­tus Au­dio should re­ally re-de­sign its rear panel art­work so as not to po­ten­tially mis­lead cus­tomers into think­ing it has a phono in­put, or that a phono stage can be fit­ted, be­cause it cer­tainly fooled me into think­ing this.

As for the DAC mod­ule it­self, ac­cord­ing to Vi­tus it uses the most ex­pen­sive IC avail­able from US-based chip man­u­fac­turer ESS Tech­nol­ogy. ‘ Many con­sider this the best-sound­ing DAC avail­able, and equally as many find it a bit “dig­i­tal and cold”, to which I do per­son­ally stand some­where in the mid­dle,’ says Hans Ole Vi­tus. ‘ It was cho­sen ini­tially based on our wish to fully sup­port DoP, which only very few DAC chips do for real. Ob­vi­ously we cre­ated a de­sign around the DAC which gave us the mu­si­cal­ity we al­ways strive for, seek­ing for all those emo­tions that all mu­sic has, but is so of­ten for­got­ten.’

When you se­lect any in­put, the se­lected in­put name ini­tially shows on the RI-101’s or­ange-coloured front panel dis­play as ‘In­put 1’, ‘In­put 2’ and so on. How­ever, by us­ing the front panel push­but­tons you can change these names to re­flect the com­po­nent type con­nected to any in­put (CD, Tuner etc) either by se­lect­ing from a pre-pro­grammed list, or by typ­ing in your own per­sonal iden­ti­fier, such as ‘Son­dek’ or ‘Pro-Ject’ (as­sum­ing you have con­nected a turntable by us­ing an ex­ter­nal phono stage, such as Vi­tus Au­dio’s own RP-102.)

Your abil­ity to cus­tomise each in­put does not stop there. You can also ad­just the gain of each in­put by up to ±12dB to en­sure that the vol­ume level of your speak­ers does not change when you switch from, say, your tuner to your CD player. Also, if you are not us­ing all five in­puts, you can in­struct the RI-101 to not show any un­used in­puts on the front panel dis­play. This is par­tic­u­larly handy be­cause you can’t se­lect in­puts di­rectly, either from the front panel or from the re­mote con­trol. If you’re us­ing In­put 1 and want to se­lect In­put 4, you first have to se­lect In­put 2, then In­put 3 (and vice versa). Yet an­other op­tion is that you can se­lect a par­tic­u­lar vol­ume level for any in­put, and then ‘fix’ it, so that that this vol­ume level will be used ev­ery time you switch to that in­put. If you do this, how­ever, the vol­ume con­trol will not be op­er­a­tional for this in­put: the vol­ume level is truly ‘fixed’. (Though you can ‘un­fix’ it any time you like, of course.) Although I am cer­tain that this fea­ture is pri­mar­ily in­cluded to en­able the RI-101 to be used in a multi-chan­nel sys­tem (likely pow­er­ing the front main speak­ers) I can think of other use­ful im­ple­men­ta­tions for it. For ex­am­ple, if you ‘fixed’ all five in­put lev­els, you could en­sure that a cer­tain vol­ume play­back level was never ex­ceeded in your lis­ten­ing room… at least un­til the kids work out what you’ve done.

Since I am men­tion­ing vol­ume lev­els, you can also pre­set a ‘de­fault’ switch-on vol­ume and a ‘re­sume’ switch-on vol­ume. The idea of the ‘re­sume’ vol­ume is that if you set it, when you turn on the am­pli­fier from Standby it will not only de­fault to the last in­put you used, but also to the vol­ume level you pro­grammed. If you do not set the ‘re­sume’ switch-on vol­ume, the am­pli­fier will al­ways de­fault to the last in­put, but the vol­ume it­self will au­to­mat­i­cally de­fault to –99dB… which is ef­fec­tively no sound at all!

The dif­fer­ence be­tween the ‘de­fault’ and ‘re­sume’ set­tings is that the ‘re­sume’ set­ting will dis­ap­pear af­ter a ‘no power’ event (such as the am­pli­fier be­ing un­plugged, or a mains power out­age) while the ‘de­fault’ vol­ume set­ting, on the other hand, will al­ways be re­tained.

Vol­ume level can be man­u­ally ad­justed by us­ing the ‘Vol­ume Up’ but­ton (the top­most of the three but­tons to the right of the front panel dis­play), or the ‘Vol­ume Down’ but­ton (the bot­tom-most of the three but­tons). The but­ton in the mid­dle is ‘Mute’. The three but­tons on the other side of the dis­play are (from top to bot­tom), In­put/Up, Menu/ Se­lect and Standby/Down and are used for In­put Se­lec­tion and Power Switch­ing, plus se­lect­ing and set­ting the pre­vi­ously-men­tioned in­put op­tions (about which I’ll say more later in this re­view).

The DAC mod­ule, ac­cord­ing to Vi­tus Au­dio, uses the most ex­pen­sive IC avail­able from US-based chip man­u­fac­turer ESS Tech­nol­ogy

Still on the sub­ject of vol­ume level con­trol, an­other in­ter­nal change on the RI-101 is the vol­ume con­trol cir­cuitry it­self, which now uses the same sys­tem that’s em­ployed in Vi­tus Au­dio’s SL-103 and MP-L201 (a re­lay-con­trolled switched re­sis­tor net­work) but a slightly dif­fer­ent im­ple­men­ta­tion of it. Be­cause Vi­tus en­cap­su­lates its power trans­form­ers, I was un­able to de­ter­mine if the one in the RI-101 was the same as the one used in the RI-100, and Vi­tus Au­dio says only that it: ‘ has the same rat­ing’ (which would put it at 1kVA, ac­cord­ing to the Vi­tus web­site) but that the com­pany has been able to: ‘ im­prove the ef­fi­ciency of the trans­former’… although the means by which it has been able to do this are un­known. Power sup­ply stor­age/smooth­ing ca­pac­i­tance is 216,000μF per chan­nel, up from the claimed 120,000μF per chan­nel in the old RI-100.

One as­pect of the cir­cuit de­sign that has not changed is the topol­ogy of the out­put stage, which is bridged ( aka ‘bal­anced’), which in this im­ple­men­ta­tion means that Vi­tus is us­ing two sep­a­rate am­pli­fiers per chan­nel, with each am­pli­fier pow­er­ing one leg of a dif­fer­en­tial sig­nal. This cir­cuit topol­ogy means twice as much volt­age swing and twice as much power (so the­o­ret­i­cally four times the power), plus lower noise.

How­ever, it also means twice the dis­tor­tion and twice the out­put im­ped­ance (and there­fore half the damp­ing fac­tor).

From a prac­ti­cal view­point as an end-user, the bridged de­sign means that the ‘neg­a­tive’ speaker ter­mi­nal is ac­tu­ally car­ry­ing volt­age, so it is not at ground po­ten­tial and should never be con­nected to any earth or any ‘neg­a­tive’ ter­mi­nal on any other elec­tronic com­po­nent (such as a pow­ered sub­woofer). To its credit, Vi­tus puts very large warn­ings on the rear panel of the RI-101 along­side both sets of speaker ter­mi­nals, how­ever the ter­mi­nals them­selves still use red and black-coloured speaker posts, whereas the con­ven­tion these days is to use red and blue colours (with the blue colour serv­ing as a vis­ual warn­ing to any­one who can’t read English that the ter­mi­nal is po­ten­tially not at earth po­ten­tial). It is also be­com­ing com­mon to put ‘light­ning bolt’ sym­bols along­side both speaker ter­mi­nals of an am­pli­fier with bridged out­puts as yet an­other vis­ual warn­ing to be care­ful, but these were ab­sent on our RI-101.

Although the Vi­tus RI-101 is phys­i­cally a very large am­pli­fier, mea­sur­ing 435×195×435mm (WHD), this doesn’t re­ally pre­pare you for its weight, which is 40kg, mak­ing it al­ways a two-per­son lift. A com­pli­cat­ing fac­tor when lift­ing the am­pli­fier is that the feet un­der­neath the case are very squat, so there’s only about a 13mm gap un­der­neath the chas­sis at the sides which means that you can’t eas­ily get your fin­gers right un­der­neath the am­pli­fier to lift it… only your fin­ger­tips. Fit­ting larger feet would make a huge dif­fer­ence.

The am­pli­fier’s war­ranty pe­riod seems rather short for a prod­uct of the Vi­tus Au­dio RI-101’s ob­vi­ous qual­ity, and the war­ranty con­di­tions a tad un­usual and un­set­tling. I sug­gest you read them very care­fully.

In Use and LIs­ten­Ing ses­sIons

Take a look at the pho­to­graph of the rear panel of the Vi­tus Au­dio RI-101 and you’ll see that Vi­tus has been very clever with the let­ter­ing printed on it, be­cause all the let­ter­ing for the one chan­nel is printed in red paint, and all the let­ter­ing for the other chan­nel in white paint. There are no ‘left’ or ‘right’ chan­nel in­di­ca­tions, so you could choose either, but we’d opt for the right chan­nel be­ing the one with the red mark­ings.

I did find, how­ever, that un­der less-than-op­ti­mum light­ing con­di­tions, I found it was al­most im­pos­si­ble to read the red print­ing, whereas the white print­ing re­mained per­fectly vis­i­ble. Maybe bright or­ange or yel­low would have been a bet­ter colour choice than red. I’d sug­gest that in the event of a change of heart about the colour scheme of the let­ter­ing, Vi­tus should also take the op­por­tu­nity to re­move the ref­er­ence to ‘RIAA’ from In­put 5, cor­rect the in­cor­rect spell­ing of ‘Im­proper’ on the ground ter­mi­nal warn­ing (you can check the mis­spelling on the pho­to­graph of the rear panel) and add the let­ter ‘s’ to the word ‘cir­cum­stance’ in the two speaker ter­mi­nal warn­ings in or­der to make the warn­ings gram­mat­i­cal.

All the rear panel ter­mi­nals are re­cessed a lit­tle, so there’s ex­cel­lent plug pro­tec­tion, but the speaker ter­mi­nals don’t have through­holes, and the ter­mi­nal heads don’t wind off fully. This means bare wires are a lit­tle dif­fi­cult to at­tach and that you can­not use eye­let-style (ring-style) con­nec­tors at all.

One as­pect of the cir­cuit de­sign that has not changed is the topol­ogy of the out­put stage

This means your speaker ca­bles re­ally need to be ter­mi­nated in either spade con­nec­tors or ba­nana plugs.

I was re­ally im­pressed by the re­mote con­trol Vi­tus Au­dio pro­vides as stan­dard with the RI-101. It’s a sleek, beau­ti­fully de­signed and beau­ti­fully-made re­mote con­trol that looks ex­actly like an Ap­ple TV re­mote. But it not only looks like an Ap­ple TV re­mote… it is an au­then­tic Ap­ple TV re­mote, made by Ap­ple it­self. Although the RI-101 Own­ers Man­ual says that it’s nec­es­sary to ‘pair’ this re­mote with the RI-101 be­fore it can be used, mine was us­able ‘out of the box’ so Vi­tus is ob­vi­ously do­ing the pair­ing at the fac­tory.

My first task was to set the in­put la­bels to match my re­view set-up, and to set the vol­ume con­trol de­faults. This wasn’t as easy as I thought it might be, be­cause I found it dif­fi­cult to nav­i­gate through the menus us­ing the front panel but­tons (and the re­mote can’t be used for menu nav­i­ga­tion). For ex­am­ple, do­ing some­thing as sim­ple as set­ting the de­fault ‘start’ vol­ume for a par­tic­u­lar in­put is a process that re­quires you to press the ‘Down’, ‘Up’ and ‘Se­lect’ but­tons 25 times, in an ex­act se­quence. Then to change the gain on that in­put re­quires a fur­ther 21 equally pre­cise pushes of var­i­ous but­tons. If you then want to change the name to, say, ‘Tuner’, you’ll be press­ing but­tons un­til the prover­bial cows come home. In­deed the var­i­ous pro­gram­ming steps and pro­cesses are so ar­cane that Vi­tus has in­cluded more than half-a-dozen step-by-step ex­am­ples of ex­actly what to do and how to do it in its Own­ers’ Man­ual. I would rec­om­mend you fol­low these ex­am­ples care­fully, and put aside a fair bit of time to get done what you’d like to do… or bet­ter still, just wimp out and get your dealer to do it for you!

One of de­signer Hans Ole Vi­tus’s stated in­ten­tions in re-vamp­ing the RI-100 de­sign to RI-101 sta­tus was, in his words: ‘ To bring the sound a bit closer to the SIA-025 “sound” if you like, and then even of a few tech­ni­cal as­pects— like the res­o­lu­tion of the vol­ume con­trol—a bit fur­ther!’

I was left in no doubt that he’s cer­tainly ad­vanced the sound qual­ity of the RI-101 a lot fur­ther in the di­rec­tion of the SIA025. Let’s look at the bass regis­ter just for starters. Whereas in Eso­ter­ica’s re­view of the RI-100 it was stated that the bass regis­ter was ‘gen­er­ous’ and ‘bloomy’, and that it brought ‘ex­cite­ment’ and ‘body’ to leaner record­ings, the same re­view men­tioned that bass-heavy pro­duc­tions could be­come a tad over­cooked.

The new RI-101 re­tains the ex­cite­ment and body of the bass de­liv­ery, but its per­for­mance is now in­de­pen­dent of the qual­ity of the record­ing, so that bass-heavy record­ings are still bass-heavy, but are never ‘over­cooked’ and like­wise record­ings that are lean in the bass are kept as lean-sound­ing as the artist and pro­ducer orig­i­nally in­tended. The new ver­sion of the RI-101 does not try to ‘fix things in post’… as they say.

The low-fre­quency dy­nam­ics and the dex­trous­ness of the tran­sient at­tack of the Vi­tus RI-101 are im­pres­sive and its pace, rhythm and tim­ing are ab­so­lutely spot-on. Lis­ten­ing to Black Cock­a­toos, which is the opener on Big Merino’s de­but al­bum, ‘Sub­ur­ban Wildlife’, you can hear the way PRAT is main­tained per­fectly, yet the mu­sic is still de­liv­ered with a lazy, laid-back feel. And when the more rhyth­mi­cally tight track How Can You Be So Sure fol­lows, you can hear the ‘feel’ of the track tighten.

It’s cru­cial that an am­pli­fier can de­liver the en­tire vo­cal range, from bass to so­pranino, with to­tal pre­ci­sion, and I found that the Vi­tus RI-101 did this ef­fort­lessly. I stuck with Sub­ur­ban Wildlife (a high ro­ta­tion al­bum at Eso­ter­ica HQ) and the sound of Stu­art Davis’ vo­cal on Turn This Boat Around was amaz­ingly ac­cu­rate… it was pretty much like I was lis­ten­ing to him live at the Peter­sham Bowlo: you can cer­tainly hear how well he honed his vo­cal skills with Tony Back­house’s Heav­enly Light Quar­tet.

I lis­tened par­tic­u­larly to the in­cred­i­ble trans­parency of the Vi­tus Au­dio RI-101’s sonic de­liv­ery in the open­ing bars of Turn This Boat Around as well as the su­perb stereo imag­ing (and the ab­so­lute sep­a­ra­tion be­tween the two stereo chan­nels) that was clearly audi­ble on Love Let­ter From A Fool, a track that also fea­tures the de­li­cious sound of guest bassist Jonathan Zwartz, plus some great lead gui­tar from Alex Craig.

Be­tween them, Davis and Craig wrote all the tunes on this al­bum, but I could not work out whether Love Let­ter was an homage to Leiber and Stoller’s fa­mous song Love Po­tion No 9, or just an un­wit­ting imi­ta­tion. Just lis­ten to Davis singing his lyric ‘ love hit me from be­hind’ and com­pare it to The Searchers’ John McNally singing ‘ love po­tion num­ber 9.’ Po­ten­tial kook­aburra con­tro­ver­sies notwith­stand­ing (!), this is a great al­bum, made even bet­ter by the pedal steel con­tri­bu­tions from Michel Rose and brass con­tri­bu­tions from James Green­ing… not to men­tion the tasty key­board work of John Gauci.

If your tastes lean more to New Age, you’ll be as­tounded by the way the Vi­tus RI-101 de­liv­ers the in­cred­i­bly lush sound­scapes that are cap­tured on ‘Flow’, which is a col­lab­o­ra­tion be­tween Will Ack­er­man (gui­tar and pro­duc­tion), Fiona Joy (pi­ano and vo­cals), Lawrence Blatt (gui­tars and uke) and Jeff Oster (trum­pet, flugel­horn) who, when play­ing to­gether, call them­selves ‘Flow’. The acous­tic gui­tars are close-miked, so you can hear fin­ger­tips mov­ing on metal strings, as well as the sounds of fret­ting. And be­ing New Age, there’s lots hap­pen­ing up in the high fre­quen­cies, in­clud­ing var­i­ous bird and en­vi­ron­men­tal noises. Joy’s pi­ano is recorded very close, with a re­veal­ing in­ti­macy. But ‘Flow’ is not all New Age. Wait­ing for Sun­shine is quite bluesy and Wa­ters Gather Ny­man-like, while Tenth Life seems to have En­nio Mor­ri­cone writ­ten all over it. I loved the mu­sic and was en­rap­tured by the son­ics, par­tic­u­larly as de­liv­ered by the RI-101. I could hear all the sep­a­rate strands of the mu­sic as the notes in­ter­leaved, and the back­grounds were to­tally si­lent, but with­out that ‘black­ness’ that can some­times deaden the acous­tic.

The Vi­tus RI-101 is an ex­tremely pow­er­ful am­pli­fier. There’s no way you’ll be want­ing for more power than it de­liv­ers, no mat­ter how de­mand­ing your loud­speak­ers. Orches­tral mu­sic is per­haps the most de­mand­ing on an am­pli­fier’s power re­serves, but the RI-101 was more than up to re­pro­duc­ing Beethoven’s Fifth Sym­phony at near-con­cert lev­els, with no hint of over­load and, when the orches­tra was not play­ing, re­pro­duc­ing very ac­cu­rately the minu­tiae of au­di­ence noise. Even Mahler’s Eighth Sym­phony, with its huge cho­rus and orches­tra, did not faze the RI-101 one iota, with the am­pli­fier de­liv­er­ing an ab­so­lutely match­less, in­tri­cately-lay­ered sound­field, ir­re­spec­tive of how loudly—or, in­deed, how qui­etly—I de­cided to play it. Even the more modern may­hem of Red Sea’s Bat­tlescar (track and al­bum both) could not un­set­tle the Vi­tus RI-101’s com­po­sure… though Pete Kelly’s ma­chine-gun drum­ming cer­tainly un­set­tled the com­po­sure of my loud­speak­ers’ bass driv­ers! Like­wise Kelly’s per­cus­sion work on Rap­ture, in com­bi­na­tion with the driv­ing bass gui­tar of At­tila Mu­rare, all over­laid by the al­most ethe­real vo­cal of Erica Bowron pierc­ing through as only she can, was de­liv­ered with a re­al­ism that was as jaw-drop­ping as it was ear-shat­ter­ing.

CON­CLU­SION

With all its prod­ucts de­signed and built en­tirely in Den­mark, Vi­tus Au­dio unashamedly spe­cialises in the über high-end of the au­dio world, a strat­egy clearly ev­i­denced by the fact that the RI-101, at $22,000—or $27,990 if you op­tion in the DAC—is the com­pany’s en­try-level in­te­grated am­pli­fier… its low­est-priced of­fer­ing. It’s also a high-per­for­mance in­te­grated am­pli­fier that sounds ab­so­lutely splen­did.

Read­ers in­ter­ested in a full tech­ni­cal ap­praisal of the per­for­mance should read the LAB­O­RA­TORY RE­PORT pub­lished on the fol­low­ing pages. Note that the re­sults men­tioned in the re­port, tab­u­lated in per­for­mance charts and/or dis­played us­ing graphs and/or pho­tographs should be con­strued as ap­ply­ing only to the spe­cific sam­ple tested.

Lab­o­ra­tory test re­port

Newport Test Labs mea­sured the power out­put of the Vi­tus Au­dio RI-101 with just a sin­gle chan­nel driven as be­ing just shy of Vi­tus Au­dio’s spec­i­fi­ca­tion of 300-watts per chan­nel, with the am­pli­fier on the lab’s test bench re­turn­ing a fig­ure of 292-watts right across the fre­quency band. This is close enough to the rated fig­ure (just 0.01dB shy) that it’s eas­ily ex­plained by slight dif­fer­ences in mea­sure­ment tech­nique and/or fluc­tu­a­tions in the mains volt­age, which Newport Test Labs doesn’t keep at a con­stant 240V dur­ing this test. The Vi­tus Au­dio R-101’s out­put power dropped when both chan­nels were driven into 8Ω loads, with the am­pli­fier re­turn­ing 277-watts per chan­nel at 1kHz and 20kHz, and 270-watts at 20kHz. When both chan­nels were driven into 4Ω loads, the RI-101 on the test bench de­liv­ered 400-watts per chan­nel ir­re­spec­tive of test fre­quency when both chan­nels were be­ing driven.

Dis­tor­tion was very low, with Newport Test Labs mea­sur­ing an over­all THD+N fig­ure of 0.037% when the RI-101 was de­liv­er­ing a 1kHz sig­nal into 8Ω at 1 watt and 0.089% at 292-watts. The spec­trum of this dis­tor­tion is shown in Graph 1, and you can see that there’s a sec­ond har­monic at –72dB (0.0251%), a third at –60dB (0.1%), a fourth at –93dB (0.0022%), a fifth at –83dB (0.007%), a sixth at –105dB (0.0005%). The other higher-or­der har­monic dis­tor­tion com­po­nents vis­i­ble on this graph are each more than 105dB down (0.0005%). The dis­tor­tion spec­trum when the am­pli­fier was driv­ing a 4Ω load at the same power out­put was al­most iden­ti­cal save for the tenth har­monic, which was much lower (Graph 2).

Dis­tor­tion in­creased con­sid­er­ably when the Vi­tus Au­dio RI-101 was de­liv­er­ing 20-watts into 8Ω and 4Ω loads, as you can see in Graph 3 (8Ω) and Graph 4 (4Ω), with the har­monic dis­tor­tion com­po­nents, both odd and even, stretch­ing right up to 20kHz. Again, the dis­tor­tion spec­trum is sim­i­lar, so I’ll ex­am­ine only the 8Ω re­sult, and you can see a sec­ond har­monic at –65dB (0.0562%), a third at –68dB (0.0398%), a fourth at –92dB (0.0025%), a fifth at –77dB (0.0141%), a sixth at –98dB (0.0012%), a sev­enth at –76dB (0.0158%) af­ter which the

higher-or­der har­mon­ics were be­tween –80dB (0.01%) and –112dB (0.0002%). You can see that, on balance, the odd-or­der har­monic dis­tor­tion com­po­nents are higher in level than the even-or­der har­mon­ics: it would have been bet­ter if this sit­u­a­tion were re­versed.

CCIF in­ter­mod­u­la­tion dis­tor­tion was rel­a­tively low at 1-watt, but the un­wanted dif­fer­ence prod­uct at 1kHz (the dif­fer­ence be­tween the 19kHz and 20kHz test sig­nals) was only 75dB down (0.0177%), and there was a sig­nal at 2kHz as well, al­beit down at 105dB (0.0005%) where there’s zero chance of it be­ing audi­ble. As with THD, IMD in­creased when out­put was in­creased to 20-watts, as shown in Graph 6, where the 1kHz sig­nal in­creases to –65dB (0.0562%) and the 2kHz sig­nal to –87dB (0.0044%). The skirt side­bands either side of the 19kHz and 20kHz test sig­nals are spread across the au­dio spec­trum, with the two high­est (at 18kHz and 21kHz) at around –71dB (0.0281%).

The Vi­tus Au­dio RI-101 is a wide-band de­sign, as ev­i­denced by Newport Test Labs mea­sur­ing the 1dB down-points of its re­sponse at 7Hz and 80kHz. The low-fre­quency 3dB down­point was be­low 1Hz and the high-fre­quency 3dB down-point was mea­sured at 135kHz. The fre­quency re­sponse across the au­dio band is shown in Graph 7 for both a non-in­duc­tive 8Ω lab­o­ra­tory test load (black trace) and a load that sim­u­lates that which would be pre­sented by a small two-way loud­speaker (red trace).

The Vi­tus RI-101 is a wide-band de­sign, as ev­i­denced by Newport Test Labs mea­sur­ing the 1dB down-points of its re­sponse at 7Hz and 80kHz

The dif­fer­ences be­tween the two traces sug­gest that the RI-101 would have a fairly high out­put im­ped­ance—as in­deed its very de­sign would sug­gest—and Newport Test Labs mea­sured that im­ped­ance as 0.49Ω, putting damp­ing fac­tor at a low-ish 16.3 at 1kHz.

Given the wide­band fre­quency re­sponse, I ex­pected the Vi­tus Au­dio RI-101’s per­for­mance with square waves would be good, and I was cor­rect, as you can see from the four that ac­com­pany this re­view. The 100Hz square wave shows some tilt, in­di­cat­ing the non-d.c. re­sponse, but no tilt, in­di­cat­ing good phase re­sponse and the 1kHz square wave is nigh-on per­fect—per­haps the tini­est bit of round­ing on the lead­ing edge. The 10kHz square wave’s shape is also ex­cel­lent. Par­tic­u­larly no­table is the re­sponse of the RI101 into a highly re­ac­tive load (8Ω par­al­leled with a 2μF ca­pac­i­tor) where there’s vir­tu­ally no over­shoot—per­haps one-eighth wave height—and only one cy­cle of ring­ing.

This type of per­for­mance is usu­ally a pre­dic­tor of am­pli­fiers that are found to ‘sound good’ in sub­jec­tive lis­ten­ing ses­sions.

Chan­nel sep­a­ra­tion was ab­so­lutely ex­cel­lent—more than 103dB right across the au­dio band—as was chan­nel balance, at 0.12dB. In­ter-chan­nel phase was also ex­cel­lent, as you can see from the tab­u­lated fig­ures.

The Vi­tus Au­dio RI-101’s sig­nal-to-noise ra­tios were also ex­cel­lent, with Newport Test Labs mea­sur­ing 97dB A-weighted re­ferred to rated out­put and 83dB A-weighted re­ferred to one watt. You can see that this was pri­mar­ily low-fre­quency noise by look­ing at the noise floors of the dis­tor­tion spec­tro­grams, where the noise floor be­tween 1kHz and 20kHz is around –120dB in the one-watt graphs and –130dB in the 20-watt graphs.

Mains power con­sump­tion was high, as you’d ex­pect from such a pow­er­ful am­pli­fier, so it will pull around 135-watts from your mains when you’re play­ing at av­er­age vol­ume lev­els, and as much as 728-watts at its max­i­mum out­put. Standby power con­sump­tion is very high, at 6.27-watts, fall­ing well out­side the Aus­tralian (and prob­a­bly all other) Gov­ern­ment stan­dards, so you’d be best ad­vised to switch the am­pli­fier off com­pletely when­ever you are not ac­tu­ally us­ing it. Steve Hold­ing

Vi­tus puts very large warn­ings on the rear panel of the RI-101 along­side the speaker ter­mi­nals, how­ever Vi­tus still uses red and black-coloured speaker posts.

Power sup­ply stor­age/smooth­ing ca­pac­i­tance is 216,000μF per chan­nel, up from the claimed 120,000μF per chan­nel in the old Vi­tus Au­dio RI-100.

Graph 5. In­ter­mod­u­la­tion dis­tor­tion (CCIFIMD) us­ing test sig­nals at 19kHz and 20kHz, at an out­put of 1-watt into an 8-ohm non-in­duc­tive load, ref­er­enced to 0dB.

Graph 6. In­ter­mod­u­la­tion dis­tor­tion (CCIFIMD) us­ing test sig­nals at 19kHz and 20kHz, at an out­put of 20-watts into an 8-ohm non-in­duc­tive load, ref­er­enced to 0dB.

Graph 2 . To­tal har­monic dis­tor­tion (THD) at 1kHz at an out­put of 1-watt into a 4-ohm non-in­duc­tive load, ref­er­enced to 0dB.

Graph 7. Fre­quency re­sponse of line in­put at an out­put of 1-watt into an 8-ohm non-in­duc­tive load (black trace) and into a com­bi­na­tion re­sis­tive/in­duc­tive/ca­pac­i­tive load rep­re­sen­ta­tive of a typ­i­cal two-way loud­speaker sys­tem (red trace).

Graph 3. To­tal har­monic dis­tor­tion (THD) at 1kHz at an out­put of 20-watts into an 8-ohm non-in­duc­tive load, ref­er­enced to 0dB.

Graph 1. To­tal har­monic dis­tor­tion (THD) at 1kHz at an out­put of 1-watt into an 8-ohm non-in­duc­tive load, ref­er­enced to 0dB.

Graph 4. To­tal har­monic dis­tor­tion (THD) at 1kHz at an out­put of 20-watts into a 4-ohm non-in­duc­tive load, ref­er­enced to 0dB.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.