Think Pos­i­tive

From soft­ware to hard­ware, the Bias Amp con­cept is pos­i­tively amaz­ing – check out the colos­sal 600-watt Bias Head and its smaller si­b­ling

Guitarist - - First Play - Words Nick Guppy

dig­i­tal amp sim­u­la­tions have ma­tured at a scary speed over the past few years, and Pos­i­tive Grid has un­der­lined its rep­u­ta­tion as one of the best with a re­cent new ver­sion of its megapop­u­lar Bias Amp soft­ware. The bril­liantly de­signed app works on iOS and Win­dows plat­forms, al­low­ing users to build their own vir­tual amp from scratch as well as tap­ping into the thou­sands of ready-made patches on Pos­i­tive Grid’s ToneCloud app. Bias Amp has proved so pop­u­lar that some gui­tarists were plug­ging into au­dio in­ter­faces and us­ing it live. So, it was a nat­u­ral step for Pos­i­tive Grid to in­tro­duce its own in the shape of

the Bias Head, which prom­ises prac­ti­cally zero-la­tency op­er­a­tion, as well as the op­tion of a whop­ping 600-watt power stage. The hard­ware range has also re­cently been ex­panded with the scaled-down Bias Mini, of­fer­ing ded­i­cated ver­sions for gui­tar and bass and a 300-watt power stage.

Both heads are exquisitely de­signed and as­sem­bled; the in­ter­nals are PCB-based and un­sur­pris­ingly look more like a com­puter than a gui­tar amp. The toaster-sized Bias Head’s front panel con­trols in­clude re­as­sur­ingly fa­mil­iar knobs for gain, bass, mid, tre­ble, pres­ence and mas­ter vol­ume, while over the top of these is a sec­ond row that al­lows in­stant tweak­ing of amp type, num­ber of vir­tual tube stages, power amp topol­ogy and more.

Around the back there are bal­anced and un­bal­anced stereo out­puts, a head­phones jack, MIDI in/out/thru sock­ets, footswitch sock­ets, two ex­pres­sion pedal jacks and a send/re­turn for the pro­gram­mable ef­fects loop, USB socket and a wire­less but­ton that al­lows the Bias Head to com­mu­ni­cate with the Bias Amp mo­bile app via Blue­tooth. Tucked away in the bot­tom cor­ner are use­ful tog­gle switches that let you run the amp’s speaker and line-outs in se­rial or par­al­lel mode, for wet/dry rigs, and footswitch cal­i­bra­tion.

De­spite be­ing much smaller, the half rack-sized Bias Mini man­ages to keep most of the es­sen­tial rear panel func­tion­al­ity, while front panel con­trols stick to the es­sen­tial amp type, gain, tone and vol­ume, with a clever out­put level knob gov­ern­ing sep­a­rate lev­els for line-out, speaker, head­phones and FX send.

As both heads are pur­pose-built in­ter­faces for the Bias Amp soft­ware, you’d ex­pect in­te­gra­tion to be fault­less, and for the most part it is. On­line ac­ti­va­tion and reg­is­tra­tion is fairly straight­for­ward, with both amps hook­ing up to an iPad with­out any prob­lems. PC own­ers may need some up­dates; Bias Amp worked fine with a mod­ern Win­dows 10 lap­top, but failed to run on an older Win­dows 7 ma­chine, so check out fo­rum posts on com­pat­i­bil­ity.

The app it­self is su­perb, with beau­ti­fully drawn art­work adding to the il­lu­sion that you’re cus­tomis­ing real amps, rather than shuf­fling ‘0’s and ‘1’s in­side a DSP. Ef­fects are no­tice­ably ab­sent, how­ever, but there’s a noise gate, hum re­duc­tion and sev­eral ex­cel­lent re­verbs, with a choice of room, plate and hall al­go­rithms along­side a su­perb cham­ber. Up­grade from the stan­dard app and you can ac­cess a very tempt­ing Ce­lestion-li­censed cab mod­ule and load your choice of IR patches, as well as play

The coolest part of both heads is the way they quickly in­ter­face with desks to pro­vide that same qual­ity di­rect to a house PA or a record­ing track

with the Amp Match func­tion. Sav­ing pre­sets is quite straight­for­ward – once you’re happy with a par­tic­u­lar sound, click on ‘Save to Head/Rack’ in the pre­set menu and you’re good to go.

Both the Bias Head and Bias Mini al­low real-time tweak­ing from the front panel con­trols like any reg­u­lar gui­tar amp, and with the Bias Head you can play with more es­o­teric fea­tures, such as power amp topol­ogy, or the num­ber of preamp valve stages. The Bias Head comes with 25 pre­sets out of the box ar­ranged in five banks ac­cord­ing to type, while the Bias Mini has 16, ar­ranged in two banks of eight called Red and Green. Turn­ing the pre­set knob se­lects the patch, while tap­ping it swaps from Red to Green and back again.

Feel & sounds

The over­all qual­ity of the pre­sets on both heads is ex­cel­lent; your idea of what con­sti­tutes a per­fect AC30 or tweed Bass­man may not al­ways line up with other peo­ple’s, but there’s plenty of flex­i­bil­ity in the soft­ware to deal with that. What’s more im­por­tant is that the core tones are very us­able for both live and record­ing sit­u­a­tions, with plenty of in­stant-grat­i­fi­ca­tion patches in the ToneCloud for those oc­ca­sions when time is in short sup­ply.

The higher-gain dis­tor­tions keep noise down to re­spectably low lev­els, helped by the noise gate. We’re also very im­pressed with the lower gain voic­ings, par­tic­u­larly the glassy tre­ble com­plex­ity of the ‘’64 Bri­tish J45’ patch and the touch-sen­si­tive midrange throat­i­ness of ‘Tweed Lux’.

The coolest part of both heads, though, is the way they quickly in­ter­face with desks to pro­vide that same qual­ity di­rect to a house PA or a record­ing track. While ef­fects have to be added sep­a­rately, the built-in re­verbs pro­vide all the am­bi­ence you need for ex­cep­tional re­al­ism; the rooms, halls and plates are all very adapt­able, while the cham­ber em­u­la­tion is one of the best we’ve heard and es­sen­tial for re­cre­at­ing the vibe of early gui­tar sounds from both sides of the At­lantic. Both heads have vol­ume to spare for any size gig.


What­ever your opin­ion of dig­i­tal modelling, prod­ucts such as the Bias Head and Bias Mini def­i­nitely have their place, now and in the fu­ture, mak­ing it easy to get con­sis­tently great sounds on stage and in the stu­dio, while by­pass­ing the te­dium of tweak­ing EQs and mic po­si­tion­ing.

The play­ing ex­pe­ri­ence comes very close to the real thing, con­vinc­ingly repli­cat­ing the re­sponse and dy­nam­ics of a real valve cir­cuit. The new Bias Mini Gui­tar (and Bass) heads will open the dig­i­tal door for many new cus­tomers – they’re more ac­ces­si­ble and com­pact, mak­ing for a pow­er­ful and por­ta­ble tool, ideal for small to medium-sized gigs. They’re not cheap, but you’re not just buy­ing the hard­ware; the price also in­cludes the won­der­ful Bias Amp soft­ware and en­try to Pos­i­tive Grid’s fea­ture-rich ToneCloud por­tal.

If you’re think­ing of go­ing dig­i­tal, there’s never been a bet­ter time to think Pos­i­tive.

Photography Olly Cur­tis


This is the pow­ered ver­sion of the Bias Head, fea­tur­ing a pow­er­ful 600-watt RMS Class D am­pli­fier 1. The Topol­ogy switch lets you swap be­tween dif­fer­ent out­put stage types, such as sin­gleended and class AB push-pull on the fly

3. The Bias Mini’s Pre­set knob ac­cesses all 16 of the Bias Mini’s on­board patches, ar­ranged in two banks of eight 3

2. The Bias Mini’s clever Out­put level knob con­trols sep­a­rate lev­els for head­phones, speaker out, FX send and line-out 2

4. Both heads fea­ture seam­less edit­ing and hook-up with the Bias Amp mo­bile app, us­ing Blue­tooth wire­less con­trol 4

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