Unwanted Distortion on Clean Rigs

    Please don't shoot me for asking this. I've read and read and read and I can't find the answer.


    My guitar distorts the KPA on clean sounds. The Clean Sens doesn't help. The only way to fix it seems to be to reduce the volume on the output of my guitar.


    I have a preamp in my guitar. It's powered by 18 volts, and the gain is set for an output swing of around 10 volts (peak to peak) when playing hard. Distortion on clean sounds has never been a problem before now. On the AXE FX (as my example) I can set the input trim (or whatever it's called) to prevent distortion. Same on every other digital device I own.


    At what voltage do the input electronics clip the input signal? Please don't tell me the guitar output doesn't matter, it does. Surely if I amplified the signal going into the input up to 100 volts peak to peak the KPA would distort, correct? If that's true then what's the maximum input level before clipping supposed to be?


    I really don't want to change the preamp gain. If I do, the guitar won't adequately drive +4dB level inputs for a decent noise floor. Using the volume control is no good either since it can't be consistently reproduced.


    Solution?

    I don’t inow the answer unfortunately but would be interested to know.


    Anyway, is the input light going fully red at the same time? I’m just trying to rule out the possibility that the distortion is happening after the input converters. Ie is it in the software domain which should be fixable either by finding the right parameter(s) or by Kemper making a tweak in the OS, or is it really a hardware issue?

    I am sorry but you MUST reduce the volume on the output of your guitar without feeling that you are cutting your sound ....


    Think about this like a car... you dont need to to press the gas pedal to max all the time right?


    So go easy with the volume of the guitar unless you want a distorted heavy signal (like many ''musicien'' here)


    Just simply think :

    Clean tone volume 5

    Distortion tone volume 10


    You wont cut or change your tone you'll just avoid to sound like sh-t with your clean tones

    Personally, I use my KPA's master volume to get a similar effect on purpose. Maybe you don't have enough headroom in whatever you are using as a power amp. Headroom carries all the way through the signal chain, so you should check it at each stage.


    Input

    Stomp

    Stack

    FX Loop

    Effects

    Power Amp (I use a powered cab)


    Try disabling everything between the input and Power Amp, except the "Stack" section. This should give you the loudest, clearest output from your profile. Then one at a time, turn the other sections on, and note what they do to your overall level. You may find that something in the chain is drastically lowering the overall KPA volume.


    I had a similar problem for a while, and I found out it was a shorted cable in my FX loop, which was causing the problem. Once replaced, the overall volume jumped significantly. I've also had similar findings with stomps (some of which have their own volume) that for some reason had there volume set very low.


    Disabling and starting from just the Stack section should give you some ideas. If there is no problem in the signal chain, you may just need more headroom in whatever amp you are using. This way, you can turn down the KPA master, and still have enough output volume.

    I think the solution here is to reduce the output of the guitar like Gforce suggests. Turning the volume down on the guitar solves the problem but like I mentioned in my post, turning a volume pot down can't be reproduced exactly.


    My final solution is to make a resistive voltage divider to attenutate the signal by about 6dB, or down to 5 volts P-P instead of 10 V P-P, and put in in a little box with input and output jacks. That cleans it up. It's not a big deal. My passive guitars don't have this problem. Just the one I use the most that has a preamp distorts the clean sounds. I could turn down the gain of the preamp but then I'm raising the noise floor by 6dB when running directly into my audio interface which I do when tracking the guitar to record the clean signal.


    Thanks for the suggestions. Much appreciated.

    I’ve never had a problem with the noise floor so can’t comment directly on that. However, the obvious solution to lack of consistency with volume knob settings is to stick a volume pedal with a min setting pot in front of the input. In this case the heel position will be a fixed level of reduction rather than off completely.

    Quote from Wheresthedug

    I’ve never had a problem with the noise floor so can’t comment directly on that. However, the obvious solution to lack of consistency with volume knob settings is to stick a volume pedal with a min setting pot in front of the input. In this case the heel position will be a fixed level of reduction rather than off completely.

    My opinion:

    The noise floor when recording the guitar directly into an audio interface it critical IMO if it's going to be used for reamping with high gain rigs. Also the input impedance is typically 10K so you can't just plug a passive guitar into an audio interface without degrading the tone (unless it has a high-Z input). You need a preamp. When using high gain rigs, just a little bit of hiss gets amplified a lot. A +4dB input requires more than 20 volts peak to peak (IIRC) to take advantage of the full dynamic range of the interface. It doesn't matter if it's a 16 bit or a 24 bit system. The solution you suggest is a good one as long as it's a passive pedal. An active pedal will introduce more noise. The preamp in my guitar is home brew with a S/N ratio greater than 110dB so it adds little if any noise.


    I've got the parts for an attenuator that will do exactly what you suggested but with the flick of a switch. I'm putting a bypass switch on it to allow either attenuation or full volume.


    Thanks for the suggestion.

    Quote from sampleaccurate

    The noise floor when recording the guitar directly into an audio interface it critical IMO if it's going to be used for reamping with high gain rigs. Also the input impedance is typically 10K so you can't just plug a passive guitar into an audio interface without degrading the tone (unless it has a high-Z input).

    As far as I am aware the input of the Kemper is expecting to see a high Z unbalanced input just like a regular guitar amp. This is part of the reason it reacts so well to changes from the guitar volume and tone pots as well as picking dynamics. It then sends a Low Z signal to the DAW through the Git or Studio output options for DI, making the Kemper the DI box itself so no need for an additional DI box. When reamping it handles the conversion back, and impedance matching too, so again no need for reamping boxes etc.

    The noise flood of 24 bit digital audio is plenty high enough for passive pickups in my experience but others may have different eperiences or more discerning ears.

    Quote from Wheresthedug

    making the Kemper the DI box itself so no need for an additional DI box

    This is what I may end up doing after reducing the volume of the guitar to a more "normal" volume. It may allow to replace the direct box I use now for passive instruments going into my DAW. I need to try out some things. Thanks!

    The studio output from the Kemper is specifically intended for sending a high signal level for DI so definitely worth trying. I use SPDIF just for convenience (not because of any belief that skipping one set of AD/DA makes a significant sonic difference). I haven't used a DI box for recording/reamping for years. Prior to the Kemper I used a Torpeod Reload which also incorporates the DI and Reamping solution within a single integrated unit.

    Quote from Wheresthedug

    The studio output from the Kemper is specifically intended for sending a high signal level for DI...

    ... and its level is tied to that of the input via the Clean Sens setting if you use Gtr Studio as opposed to Gtr Anlg.


    So, if the OP rolls back his guitar-level pot and optimises the level at the KPA's input, the DI signal will indeed be perfectly-hot. Even if using the Gtr Anlg mode, this "optimum" level will be reflected at the DI out, although he'll need to use a DI or Hi-Z input on his interface or desk.


    All this doesn't negate the observation he made that technically the noise floor increases relative to the peak signal emanating from any guitar as you roll the volume pot back. IOW, a given guitar's S/N ratio's gonna be better at full tilt than when dialled back; this is true for any analogue-audio device.

    I use a Xitone Michael Britt powered 1x12 cab and when first adjusting to it many of the clean sounds had an unwanted fuzzy or distorted tone and I was considering returning it because I thought it was defective. Through email with Xitone and Michael Britt the following is what was suggested. Don't know if it will work for you but perhaps worth a try.


    The things that eliminated the issue were:


    1. make sure all cables are correct and functioning

    2. adjusting the Kemper input to avoid clipping

    3. reducing the extreme highs in the global EQ

    4. adding an IR to the stack in the very last position (this made an amazing difference)