Questions about volume behavior

  • I hope you guys can help me understand a few concepts as I don‘t seem to fully grasp the volume behavior of drives yet. I’m not sure if this is solely Kemper related or might apply to real amps and pedals as well.


    1. When I use a dirt effect like the green screamer or kemper drive, raising the effect’s volume doesn‘t seem to raise the actual output volume of the profile. Instead, the sound becomes more saturated. There is a gain boost but not a volume boost. Is that correct?


    2. All drives have at least a gain and volume setting. If my first assumption was correct, both do in fact add gain. How can we explain the difference? Does stomp box volume push the amp profile and add gain to the power amp section, whereas stomp box gain is more like adding preamp distortion?


    3. Raising “amp volume” does not effect the profile’s gain or add distortion. Unlike the last case, this one does effect the profile’s output volume. Correct?

    4. Is it correct to assume then that “amp volume” does not exist in a real amp because a real amp’s volume would always also add gain to the power amp?


    What Kemper function would be closest to a volume knob on a non master volume amp, meaning it adds output volume and poweramp saturation? Or is that not possible due to the snapshot nature of the Kemper?


    5. If I use an expression pedal or the morph function on the remote to raise the volume of a profile (for a solo, for example), I need to raise the amp or rig volume, correct? If I’d raise the drive’s volume I’d get more saturation but might not get above the mix loudness-wise.


    6. In that case, what’s the difference between raising the “amp volume” or just the entire output volume? Is it best to leave the output volume at max (or -12db) and use “amp volume” instead? (I guess instead of amp volume I could boost “rig volume” as well.)


    7. I have the feeling that drives sound best if I raise their volume by 2 or 3db or so. Is that a common phenomenon (I think I read that somewhere here) or is it due to a number of varying parameters like pickup output, profile saturation and, of course, taste?


    Thanks!

  • most of what you have described is exactly how real valve amps also behave.


    1 - an OD in front of an amp will drive the front end of the amp harder if the Volume of the FX is higher than unity (i.e. if the fx output is louder than the guitar pickup signal). The basic tone set on the amp will determine how much the volume/gain changes. On a clean sound raising the FX volume will make the amp louder and possibly add a little hair to the tone. This happens because the pre amp has plenty of headroom to handle the added volume without clipping (distorting and compressing). However, the more overdriven the amp itself is, the less added volume you will get when you raise the FX volume. In this case the preamp is already distorting and compressing the signal so it has less headroom to get louder. Once the amp is totally saturated is it fully compressed and doesn’t have anywhere to go even if you slam it with more output from the pedal.


    You can test this effect easily by removing the FX and just reducing the guitar’s volume knob. On a clean rig the volume will drop but on a dirty rig the volume will stay much more consistent but the tone will clean up. Eventually the rig will be so distorted and compressed that turning the guitar volume down will work like an on/off switch as it won’t even clean up.


    2 - both are adding gain to the pre amp. However, the gain on the pedal is clipping and compressing the signal inside the pedal so isn’t going to add much level to the output being sent to the amp. The volume on the pedal isn’t adding any clipping internally but may supply enough extra signal to cause the amp’s pre amp to clip.


    3 - Yes


    4 - No


    5 - Yes


    6 - Raise Output volume to set over all level for the gig. Use amp or rig volume to control levels of individual rigs/performances. Amp and Rig volume are virtually identical unless you have a volume sensitive FX (like a drive or compressor) after the Amp block. In this case raising Amp volume will affect the Drive or Compressor etc whereas raising Rig will just make things louder. Neither is right or wrong it just depends what you are trying to achieve.


    7 - Yes and yes ?

  • Wheresthedug Brilliant, thank you!!


    I have to say I'm quite impressed that the Kemper knows what the headroom of a profile is so it can make the right decision to either have a pedal add volume or gain or both.


    Your explanation for my question 2 makes a lot of sense. Glad to finally know what the physical (albeit of course digital in this case) process is.


    You wrote "no" as reply to my question 4. Just to clarify, did you mean to say that my assumption was correct that Kemper's "amp volume" does not exist in a real amp?

  • I believe your assumption is incorrect.

    Hm, I'm not sure I can follow. A non-master volume amp's volume knob adds gain to the power amp. A master volume amp's master volume still adds gain to the power amp while the volume/gain adds gain to the preamp. The Kemper's "amp volume" only boosts volume but doesn't add gain to the profile. Where was I wrong to assume that a real amp doesn't have such an "amp volume" button while the Kemper doesn't have a normal amp's volume knob that adds both volume and power amp saturation at the same time?


    Thanks again for your input!

  • 4. Is it correct to assume then that “amp volume” does not exist in a real amp because a real amp’s volume would always also add gain to the power amp?

    I am not an expert on the inner workings of valve amps and their schematics but from what I understand a non master volume amp basically has the master volume of the power section on 10 all the time. Turning up the volume is turning up the preamp signal therefore you could be adding pre amp gain as well as poweramp gain with that control rather than just adding power amp gain in isolation. However, thinking about it now, it is also possible that pre amp input gain is preset and it is only the amount of this already gained up signal that is let through which increases the power amp volume. That would be like opening and closing a tap.


    Although I have read a lot and watched a good few amp makers videos etc I am not an amp designer but I believe some others in the group are (or at least have enough electronic knowledge that they could be) so hopefully one of them can provide a better explanation of this particular aspect.

  • The physics are indeed interesting but ultimately not that important to me. I’m more interested in what the Kemper behavior does musically. I see that many profile creators, including M Britt, raise the “amp volume” and I not do understand why. As I believe, the amp volume does not add saturation to the profile, it only gives more output. And if I’m not mistaken, that’s a function a real amp wouldn’t have since raising the output would always effect tone.

  • The simple answer to why commercial profilers raise the amp volume in some profiles is to make them louder and therefore stand out more when compared to other profiles. It is a sort of profiler rig loudness wars. When we hear to similar sounds our ears typically trick us into thinking the louder one sounds better. I don believe it has anything to do with musical choices or trying to capture the behaviour of the real amp.

  • I try to equate much of this to a regular amp - not always correct but usually pretty close.


    Increased volume/input at pre amp stage will give modest volume but also increase gain. To increase volume only it should be at the power stage.


    Non master volume amps can;t separate the pre and post, hence had to be cranked to get decent gain....hence the master volume revolution.


    My understanding is increasing the amp volume or putting a drive pedal in front of the amp or in the first 4 slots behaves as a normal amp putting it in the pre amp stage. therefore if you want to push the amp then this is how to do it.


    Master volume is rig volume.


    Now the KPA doesn't behave exactly like this I don;t believe ( I don;t use drive pedals etc.) but similar.


    Not sure if I've answered any of your question there :)