The first parts of this review went over the basics of Bias Desktop and we liked it. Slickly designed, it also sounded great. But now we come to most exciting aspect of Bias for Desktop – the Amp Match feature.

Now Positive Grid has been whetting our appetites for this for months with a series of videos where classic amps are modelled through Amp Match and then A/B’d. Could you tell the difference? Well, to an alarming extent you could. Would what was being touted as a software Kemper turn out to be a crushing disappointment?

The answer? No – it’s brilliant, addictive, often confusing and infuriating. It is clearly an enormous step forward for what an amp sim can achieve.

But first, Amp Match is only a feature on the more expensive Professional version of the software (that extra $100 also gets the additional amp packs as well). Now many out there are not happy about the level of pricing – but this is a desktop product and exists in a different price market and in that context is still great value – after all, no software does what this can.

So with that out of the way, how does it work?Bias takes a target amp tone (or, excitingly, a pre-recorded amp tone) into your DAW, the user then selects an amp as near as dammit to the original signal and strums away while the Amp Match module samples the signal and tries to get as close a match to the original as possible. With any luck, you’ll end up with a modeled tone identical to the target signal.

I do want to make a few points – I have grossly simplified the actual process which is not totally intuitive (Positive Grid have detailed notes on the process and there are already many helpful tuition videos on Youtube). The process also requires much more user input than the equivalent Kempler process – everything depends on selecting the correct amp in the first place and there is a certain amount of art in doing that. You also have to have as  clear a target tone as possible and be warned, the process can really show up the quality of your guitar interface as well – attempts with my venerable old Line 6 UX1 were not totally successful. The process really works best when you have your target amp either plugged in or miked up, it will work with guitar tracks on recorded music but they really need to be as isolated and effect free as possible. I tried to get Alex Lifeson’s tone from Freewill  down but that hint of modulation in it defeated me.

Certainly my initial attempts were some way from what I intended. But a bit of practice helped and within a few hours my modeled amp (my old Fender Twin) was sounding much more realistic.

What the technology behind this is, is a little vague. The magnificent Music App Blog suggest a powerful EQ algorithm rather than the more sophisticated technology in Kemper. It is certainly a process that relies more on the skill and ear of the user than Kemper but it is capable of producing magnificent results in the right hands. I suspect that Positive Grid, masters at polishing the user experience, will streamline the matching process

So after some hours spent with Bias what do we have? It’s a brilliant piece of design, it sounds superb and works with other VST effects very well. The $99 basic version is a bargain. But the extra $100 gives you Amp Matching – which is a genuinely inspiring tool. This may lack the sophistication and power of Kemper but it gives you most of the features for over  $1,000 less and in a DAW environment as well.

After the relative disappointment of Revalver 4,this is the desktop amp sim I was hoping for – another triumph for Positive Grid. Now if they can only design a Bias for effects………