Unwanted Distortion When I Hit the Strings Hard

Discussion in 'Hardware, Setup & Repair [BG]' started by revelocience, Feb 4, 2021.

  1. revelocience


    Apr 22, 2020
    It's not fret buzz, I know that much. Whenever I hit the strings hard, and especially if I have the pickup dial all the way to the precision pickup and have the bass knob all the way up, it sounds like the signal is being overdriven/distorted like I have the gain too high. Gain's not the issue either, lowering it on my amp doesn't fix it. What's going on here?
  2. Jazz Ad

    Jazz Ad Mi la ré sol

    Dying battery or lack of preamp headroom
  3. revelocience


    Apr 22, 2020
    It happens even with a full battery. Wdym pre-amp headroom? What's that?
  4. Drifter8230


    Sep 4, 2020
    Have you tried lowering the pickup? I was searching for this topic today because I was getting an "overdrive" distortion. It sounded like a dying battery and/or slight distortion. It would happen when I really dug in on my B or E string. I thought it was the compression pedal at one point.

    When I lowered my pickups (EMG DC40s...very hot) the distortion went away.
    One Way and elgecko like this.
  5. 1958Bassman


    Oct 20, 2007
    How hot are the pickups? The first time I played my SD Curlee through my Tweed Bassman, it distorted pretty badly and I thought my amp had a problem. I switched to parallel and the distortion stopped. With hot pickups, the input can be overdriven. The bass has a DiMarzio Model One, which is their version of the Gibson 'Mudbucker'.
  6. jbrew73


    Dec 24, 2006
    Can you tell us what bass, strings, pickups, preamp, etc. you are using?
  7. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    Why is the bass knob dimed?

  8. kalle74


    Aug 27, 2004
    Preamp is running out of headroom, because bass is dimed. And/or amp´s preamp cannot cope with the input level. Ease bass boost on bass, crank it up on the amp. Also, as mentioned above, check pickup height and possibly lower them. I would also consider playing touch (i.e play softer, gain dexterity).
    Lammchop93, Warpeg and Drifter8230 like this.
  9. revelocience


    Apr 22, 2020
    I turned the bass down halfway and boosted in on the amp, that seems to have helped a lot, thanks! If I run into the problem again I'll check out the pickups then
  10. Jazz Ad

    Jazz Ad Mi la ré sol

    Why would you boost bass so hard ? Typically it turns to giant rattling and a blurry mix.
    It's cool if you play drone or dub, otherwise you avoid it.
    Try cutting mids and highs instead of boosting lows. As a consequence you will get more gain and a tighter tone, with less headroom issues.
    Lammchop93 likes this.
  11. rolleharris


    Nov 10, 2002
    Falun Sweden
    Thats the problem right there.
  12. dwizum


    Dec 21, 2018
    Headroom basically refers to how much of the preamp's available power you're using. I'm simplifying here, with the goal of making this more understandable.

    Imagine you're jumping on a trampoline. The height you jump to represents the output of your bass - how loud it is. Turning volume or EQ controls up means you start jumping higher - the signal gets louder. (of course, in the example of adjusting EQ, the signal only gets louder in some frequencies - but for the sake of explaining headroom, that doesn't matter - we can just discuss "louder" in general).

    Now, imagine you put the trampoline in your living room, and start jumping on it. The height of your living room ceiling is your headroom. If you've got 20 foot ceilings, you'll have no problem jumping 5 feet high. Or 10 feet high. Or 15! But if you've got 20 foot ceilings and you try to jump 22 feet high, you're going to have a problem.

    Jumping on a trampoline and hitting your head on the ceiling is equivalent to your preamp running out of headroom. You've asked for MORE than the available power it has. On the trampoline, you get a headache. On your preamp, you get distortion.

    Now, let's look at a few of the comments in this thread in light of that analogy.

    1) Your preamp's headroom is partially determined by your battery voltage. If your battery is dying, that's like your ceiling suddenly starting to sag towards the floor. You might be fine jumping 18 feet all day long, but once your 20 foot ceiling sags two feet, you will suddenly, out of nowhere, start hitting your head - even though you're playing the same as you always do.

    2) The signal your pickups send to the preamp will get bigger - louder - as you play harder. Consider the aggressiveness of your playing style as equivalent to how hard you're jumping on the trampoline. Easy analogy there. Start playing REALLY HARD and you might run out of headroom.

    3) Your pickup height also influences the strength of the signal sent to your preamp. Closer to the strings means the signal will be stronger. Think of this as the height of the legs holding the trampoline up - if you have a 20' ceiling, but your trampoline is 18' high, you won't be able to jump hard before running out of headroom. This is why pickup height comes up in these discussions. It sets a baseline for the strength of the pickup signal. If you're constantly clipping the preamp, even when playing what you consider to be gently, you can check your pickup height or just try lowering them.

    4) A bass with powerful EQ controls (like, perhaps, the bass knob you're turning all the way up) is like adding springs to your feet. You may jump 10 feet high all day long, but then if you turn the bass knob all the way up, and try to jump 10 feet high again, you find that you're suddenly jumping 25 feet even though you're exerting the same effort! The EQ knobs on your bass are analagous to the springs that give your trampoline it's "bounce."

    Someone designing a pickup and a preamp has to consider all of those things. You want a bass that is easy to control and versatile, but which won't misbehave and distort all the time. The problem is, as a designer, you have no control over things like how aggressively someone plays, how they set the knobs, how high their pickup is, how old their battery is, and so on. So, you sort of shoot for the middle ground, and then expect that bass players will be reasonable and adjust as needed. Some designers choose to keep their controls fairly tame, to avoid issues. Other designers will build systems with tons of headroom. Or they make other changes. It's part of what makes different preamps behave differently, and some are more or less appropriate for different situations.

    One last word on headroom, in case this isn't obvious. More headroom isn't inherently better unless you actually need more. If you're jumping 10 feet, it doesn't matter if the ceiling is 30 feet or 500 feet high. You will still jump 10 feet. Similarly, if you aren't using the headroom in your preamp, switching to a preamp with more headroom won't generally make a difference. I'm mentioning this because sometimes there tends to be a trend of "more must be better!" which drives things like people swapping to 18v preamps, or things like trying to mod a preamp to accept three batteries, when it's not really needed and won't make a difference.

    Actually, a second last word. Every gain stage in your signal chain functions under these rules. If you have an active preamp going into an "amp" with a preamp and a power stage, you've basically got three stages, each with headroom. As you found when you turned down the bass on the onboard preamp and cranked it up on the amp, sometimes you can "solve" issues with one stage by taking advantage of a different stage.
    ak56 likes this.
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