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Kemper Profiling Amp - a thousand flawless guitar amps in a box

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August 25, 2011

The Kemper Profiling Amp

The Kemper Profiling Amp

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Musicians are generally liberal souls but when it comes to their equipment they can be ultra-conservative - particularly guitarists. Getting their personal 'tone' and a particular 'feel' from a system of wood, wire, pickups, effects pedals, amplifiers and speakers can become a life-long struggle of incremental experimentation and bouts of pure voodoo. Over the decades certain combinations of (usually) tube amplifiers and speakers recorded using certain microphones have become known standards that feature heavily in everybody's record collection. It can be a prohibitively expensive however to keep a stable of classic tube amplifiers and, since the late 90s, the holy grail of music technology companies like Line 6 and others has been to digitally re-create these amplifiers so that hundreds of iconic tones could be stored in one box and used in the studio or live.

Unfortunately, the dynamic behavior and feel of a tube amp is an extremely complex system to understand and while many thousands of guitar amp modellers have been sold due to the sheer convenience, they could not be said to be entirely convincing. The very best available today, the stunning AxeFX from Fractal Audio, has required the mathematical modelling of almost every single component (resistors, capacitors, tubes, transformers etc.) and their interactions within a guitar amp plus the addition of some special 'chaotic' maths (hence the company name) to create credible sounds in a somewhat expensive and complex unit. In September, a new product will hit the streets that aims to do away with that complexity and within 30 seconds perfectly re-create any guitar amplifier.

Christoph Kemper is not exactly new to making digital circuits sound analog. For fifteen years his company has been making one of the finest sounding series of digital synthesizers, the Access Virus. Although not a guitarist, Christoph had always been fascinated by guitar distortion and a few years ago decided to try and finally accurately re-create a distorting guitar amplifier digitally. Rather than take the component modelling route like programmer Cliff Chase at Fractal, he and his team looked for a dynamic form of convolution (the digital imposition of one signal's characteristics onto another that is used a lot in reverberation simulations).

After a couple of years they were able to parametize what actually needed to be simulated to re-create the dynamic behavior of a tube and it's surrounding circuits. The problem was that the equations were so complex it would take an age just to model one amplifier, never mind a collection. It was at this point that Christoph decided that the amplifier being simulated could solve those equations itself and the concept of an amp 'profiler' was born, though it was another two years before a working system was produced.

To profile a given amplifier with the rather splendid-looking (and definitely Germanic) Kemper Profiling Amp you simply play through the Kemper into your amp and adjust eq, speakers, mics etc. until you have the sound you want coming out of your studio monitors. The Kemper is fed back that finished sound and switched to profiling mode. In that mode it puts a number of strange sounds through the amp chain - a low frequency 'wobble' sweep that gets louder and louder. This signal enables measurement of the dynamic behavior, frequency response and distortion of the amp. A second signal, a collection of higher frequency sine waves, allows the measurement of intermodulation distortion. When that is compared to the original sine waves a number of equations can be solved for the frequency response of the speaker on it's own. Very clever stuff and of course much of the process will remain clouded in mystery for commercial reasons.

The Kemper Profiling Amp

When the process is complete, in around 30 seconds, you can immediately compare playing through the Kemper model to your original amplifier with the press of a button - something that no other amp simulator gives you. In demonstrations the sound of the two is spookily close. But there's more. Because the process separates out several amplifier parameters those characteristics can be manipulated well beyond what a physical amp would be capable of. The gain and distortion of relatively clean amps can be pushed, power "sagging" can be manipulated for a more modern or vintage feeling amplifier. The guitar pick sound portion can be increased or the amp compressed for greater sustain. The speaker cabinet size and tone can be manipulated independently and there are of course a set of traditional Bass Middle Treble Presence tone controls.

Rounding off the features are four virtual effects pedal slots before the amp sim, modulation, delay and reverb slots after the amp sim and an external effects loop to provide a complete guitarist's rig.

As you might imagine there is considerable excitement amongst guitarists to see whether the Kemper Profiling Amp performs as promised. The possible downsides are the "handbag/lunchbox" form-factor, that you really need access to a decent studio set-up to profile amplifiers properly (though of course a whole collection of amp profiles will be supplied with the unit), and the price, which at a projected US$1,900/1,900 euro is a little more than was originally suggested and not far off from the deeply capable AxeFX2 at $2,600. That said, the AxeFX is made in relatively small numbers and is only available directly from the manufacturer. The Kemper will be mass produced and the price projected is the full retail so street prices will be lower. If this unit truly feels like a classic tube guitar amp to play then it will represent something of a seismic shift in the conservative world of guitar gear.

About the Author
Vincent Rice Vincent Rice has been an audio-visual design consultant for almost 30 years including six years with Warner Brothers Cinemas. He has designed several large retail installations in London and a dozen major nightclubs across the world from Belfast to Brno to Beruit. An accomplished musician and 3D computer graphics artist, Vince also writes for AV Magazine in the U.K. and the Loudscreen digital signage blog.   All articles by Vincent Rice
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13 Comments

Well, I forced myself to listen to all of this and finished up non-the-wiser! Possibly because I couldn't hear most of the commentary behind the constant guitar playing.

Please tell me if I'm thick, but I can't see the point behind the set-up. Can anyone explain what's going on?

Ian Colley.

TexByrnes
26th August, 2011 @ 09:25 am PDT

Hi Tex,

I agree - the guy playing the guitar was really annoying; he kept playing at completely unnecessary points in time (perhaps Dave thought it was really all about him?).

Also, I got the sense he didn't really understand the main point either - which was primarily about creating a profile of the original amplifier. The most important demonstration should have been that, after profiling, the sound should have been the same when switching between the Kemper amp and the original Tyler amp. That point was really lost in the racket he was making.

The other video is more helpful. Somewhere around 2:30 the explanation of how the process works is given. The following is what I inferred anyway:

You connect the Kemper to the original amp, the original amp drives the speaker cabinet. The speaker cabinet is mic'ed up and the mic' connects back to the Kemper.

The Kemper generates a set of reference signals into the original amp and analyses the result coming back from the microphone. Chris doesn't really make it clear whether it's also necessary to generate some signals by also playing the guitar into the loop (surely, otherwise why connect the guitar until after the profiling process). During that analysis, it calculates a set of key parameters for that sound that will be used in its own digital synthesis. Then I think it does some iterative looping, starting with that initial set of parameters, driving the original amp again, measuring the result, and refining the parameter value set.

By the time it is finished, it should be possible to plug in the guitar and switch between the original amp, and the output generated by the Kemper through the same speaker cabinet and the sound is, ideally, indistinguishable in each case. That is, you should be able to disconnect the original amp and use the Kemper instead and have an effective replica of the original.

Then, as they say, you could go on and fiddle the parameters determined by the Kemper - away from the original sound or, perhaps, to further fine tune it based on your own ear rather than just the smarts of the Kemper.

And, finally, there's the idea that you could download parameter profiles for any amp as created by other people doing the analysis using their own profiling amps, to effectively give you "many amplifier models in one box."

That's my take anyway.

martin
26th August, 2011 @ 09:18 pm PDT

martin:

you should be their public relations rep. you did a much better job of explaining it then mr. kemper did!

also, to me, the big plus would be that you could download other amps. otherwise you have to go around finding amps to record.

hopefully in the real world, it doesn't sound digital like the line6 equipment, which is much better than nothing, but still not the holy grail.

thanks for your explanation as it sure helped me!

mikeB.

muscmp
28th August, 2011 @ 12:03 pm PDT

Imma gonna profile a Kemper Profiling Amp profiling a Kemper Profiling Amp.....Ad infinitum! Muahahahaha!

Ken Witwer
28th August, 2011 @ 12:16 pm PDT

I wonderful if I could profile my voice? Then I could get other people to sing or talk for me and I could go on vacation!

Brent Joseph Peterson
29th August, 2011 @ 11:11 am PDT

So now that I have this amazing and expensive device, I have two amps that sound exactly the same. Im lost, why buy something to recapture what you already had? You could have bought another amp altogether... Just saying

Jamie Palmer
30th August, 2011 @ 03:16 am PDT

Jamie,

I'm sure it'll come loaded with a bunch of the classics (standard procedure these days),

and any time you run into a great sounding amp at a jam or something...well, you can pretty much steal it. And tweak them all to taste.

Seems like an excellent tool to have, especially if you're still looking for that tone in your head that is your voice.

FastGuy
1st September, 2011 @ 07:18 am PDT

Jamie, how about having all your rigs, other famous rigs, your friends' rigs etc. on stage in one package ... or in your bedroom or at practice.

that concept has some appeal

phill
2nd September, 2011 @ 10:36 am PDT

Hi Martin,

Thanks for your detailed analysis, I'm still not happy about how the information gained from using reference signals is meant to be used however, surely playing the unit in series/tandem with any other amplifier would introduce many other variables, so bringing you back to square one?

I'll have to mull this all over and get back!

Thanks again, Ian Colley [Tex].

TexByrnes
3rd September, 2011 @ 02:23 am PDT

Hello everyone

But I think we're forgetting one small detail ... With what will reproduce the sound? Surely this device will work well for the profiling of the amplifier, but in order to listen in the best way, you should pay particular attention to the monitor used for playback ...

It 'easy to conclude that not sound like a real amp simply is bad because we used the monitor ...

gbrdnl
19th September, 2011 @ 08:15 am PDT

A wonderful concept. Very impressive indeed.

Roger Glyndwr Lewis
23rd September, 2011 @ 03:49 am PDT

cool, just found the website where you can buy the original kemper amp case with the kemper logo! check http://megacase.com ...seems that this german case company build the orginial case for kemper

Object Dyed
3rd February, 2013 @ 05:40 am PST

Another failed attempt at emulating things you cannot. Unless you are tone deaf or just enjoy cheese, you cannot put enough effects on the amp to cover up the horrible soul destroying tone it emits.

Kenneth Liddle
10th June, 2013 @ 06:52 pm PDT
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