FAQ    

How Does Profiling Work

It took us several years of research and development to have the Profiling algorithm up and running. This chapter might be of interest for the more technically-minded amongst you.

Initially, we focussed our attention on existing and well-documented techniques, most of which fall under the heading “Dynamic Convolution”. Even though these approaches seemed very promising at first glance, and certainly useful for recreating simple, soft distortion circuits, they were by no means adequate for complex guitar amplifiers with heavy distortion. Reality has shown that no other company has managed to create a profiling amp by these methods so far.

Other well-known modeling methods, such as a distortion devices framed by a pre- and post-equalizer, have been used in modeling amps of the first generation. They deliver reasonable results, but the sound still lacks complexity, depth and feel; furthermore, these methods don’t qualify for an automated profiling procedure.

So, we had to go much deeper and, in the process, developed our own technology. A tube amp has dozens of dimensions in sound; consequently, the equation of the profiling algorithm needed dozens of variables to exactly recreate the sound and feel of the original amp. We spent considerable time researching the dynamic behavior of the tube. It was also necessary to study the interactions between the tube and surrounding circuits, which become very complex when the tube starts to distort. We were lucky to find a way to extract this exact tube behavior by analyzing the intermodulation products of crossing sine sweeps. The relation between the intermodulations and the unprocessed sine sweeps tell us the full story about the distortion shape and dynamic of the tube and the behavior of the surrounding circuit. It can even deliver the information about several distortion stages in a row, so long as there is only one stage significantly distorting. This measurement is independent of the frequency response of the amplifier. Once the distorting part has been analyzed, it can be separated from the transfer function. The frequency response of the cabinet is then easy to determine and separate.

Aside from the ease of profiling the whole amp, there is another good reason not to analyze the amp part by part: we capture the sound of every component at the place where it belongs, including all interactions between the components.

Is it a Snapshot

In the previous section, we have seen that the Profiling Amplifier will not just take a snapshot of your tube amp, but give you the same, and often deeper, control of your sound than your original amp can provide.

Once you have stored your profile, you are free to capture more profiles of your tube amp. Try different microphone positions for different flavors, or maybe find another sweet spot of your amp's controls. If this is not enough for you, you can then step into the DNA of your profile and discover new sound possibilities, based on the amp that you are familiar with. An absolutely unique, and previously unknown, feature set is waiting to tweak the dimensions of your profile to unimaginable depths:

Amp Definition is a parameter that has been pre-adjusted by the profiling process; it tells you whether the sound leans more towards a vintage or modern direction. Increase this parameter to intensify the touch response of the virtual tubes.

Power Sagging will let the tubes breathe with your playing; damped strings will have more energy, and clean, picked notes will cut through better when you reduce the playing volume.

The Pick parameter will control the attack of your pick independently of the Gain setting, even through heavy distortion. Definitely a highlight of this feature set, this innovative parameter lets you decouple your pick sound from the natural compression of the distorting tubes and cut right through the mix. Works on clean sounds, too! Often attempted in the studio environment, this is an effect that cannot be achieved by any equalizer or compressor.

The Amp Compressor will sustain the clean guitar when you play soft, but lets the distorted sound through, unprocessed, when you revert back to normal playing volume.

The Cabinet Warp parameters will give you access to the formant frequencies and character of the cabinet sound. Change the virtual size of your cabinet, tune the bass resonance and control the character of your sound in an intuitive way.

Does this sound too scientific to you? It isn’t! With a few simple tweaks you can push your sound into as yet unknown realms of feel, touch-response and depth.

We have seen the expression of many a guitarist, when switching back to the original profile they started from - it's a look that says: "Why didn't I press Store?".

 

 

Work

The Profiling Amplifier captures the sound of a tube amplifier and speaker cabinet via a microphone; by this method you can permanently capture either a studio or live situation for future use. The amp to be profiled is attached to the effects loop of the Profiling Amplifier. The Send jack will feed the unprocessed guitar sound and the profiling test signals to the guitar input of the reference amplifier. The microphone sound will be sent back to the Profiling Amplifier's Return input. In this configuration, the Profiler has total control over the reference amp, and an A/B comparison between the profile and the original can be made easily with the Compare function

Gain

Yes and no. The gain control is likely to sound the same at different positions. On some tube amplifier models we have found that the original gain control will change the tone of the guitar a bit, which is not actually an advantage. Some cut the high frequencies of the guitar when you turn it up, and some cut the low frequencies when you turn it toward a clean sound, resulting in a somewhat thin sound. We have kept our gain control neutral, so you can find the sweet spot of your amp, and run this optimal sound at any gain level. If it is demanded by our users, we can easily provide appropriate gain models or ways to capture the whole gain behavior.

In addition to all this, our gain control goes far beyond the scope of classic tube amplifiers. On the Kemper Amplifier you can control the gain of your profile within an incredible range of 80 dB from crystal clean to insanely distorted - no need for an additional booster to create your favorite lead sound!

The Profiling Amplifier will capture the momentary settings of the tone controls that represent the sound you dialled on your tube amp. We were requested by many guitarists to develop a tone stack for the Kemper Amplifier that reacts like a classic tone stack, but with more impact and range. When you profile your amp, these new tone controls will be positioned in the mid setting. We have plans to add models of original passive tone stacks of popular amps; these can be chosen for profiling the corresponding tube amp and will give you the sound of your original tone controls at any position.

If you create and store a profile of your favorite amp with all the tone controls set to the middle position, we will later have the chance to create the corresponding tone stack, so you can add it seamlessly to your profile afterwards.

Updates

Absolutely! Our Virus Synthesizer range is based on a continuous development of 15 years (and counting!) - a legacy that is unique in synthesizer history. We have built our reputation on software improvements and updates that have been available free of charge on the internet since way back in 1996. We are not aware of any company providing free software improvements to their customers before we started doing so, and we feel a bit like the “inventor” of this service. We will certainly continue in that spirit with the Kemper Profiling Amplifier!

Who is Kemper

Kemper is new to the guitar world, but an old player in the keyboard world. In 2011 we are celebrating the 15th anniversary of developing and producing the Access Virus Synthesizer, one of the most successful line of synthesizers in history, and for which we have won numerous awards.

 

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