18 Volt power?

Discussion in 'The Stomp Box' started by pete-strych, Apr 18, 2015.

  1. pete-strych

    pete-strych Tele-Holic

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    What's the benefit of running an Overdrive or Distortion pedal at 18 volts instead of 9 volts.
     
  2. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    Increased headroom/dynamic range.
     
  3. Mr. Lumbergh

    Mr. Lumbergh Poster Extraordinaire

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    I have a compressor that advertises it runs better at 18V, but 18V for me just caused a terrible buzz. If they advertise it can run at 18, try it, otherwise don't mess with it.
     
  4. motwang

    motwang Tele-Afflicted

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    18 volts ACor DC, it makes a difference!!!
     
  5. pete-strych

    pete-strych Tele-Holic

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    Uuugggh...DC
     
  6. Coop47

    Coop47 Poster Extraordinaire

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    +1 - Don't try it unless you know for sure the pedal can handle it.
     
  7. jmclaren

    jmclaren Tele-Holic

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    I've read many times that using 18 volts into an OD pedal that's built for it will produce more headroom. Why would anybody want more headroom in an OD pedal?
     
  8. drmcclainphd

    drmcclainphd Tele-Afflicted

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    For dynamic range. So you can get the OD sound whether you're playing quiet or loud. Think "Oh Well" by (old) Fleetwood Mac. This overcomes the tendency of OD to compress.
     
  9. Tim Bowen

    Tim Bowen Poster Extraordinaire

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    The differences can vary from circuit to circuit (pedals), but often we're talking fairly subtle. When playing at home it probably doesn't matter all that much, at least in my opinion.

    When the additional headroom starts to matter is somewhat cumulative. Playing live with a loud rock band with a heavy hitting drummer, with an amp that's breaking up moderately but doesn't have a ton of headroom to spare - that's a recipe for benefit from additional headroom from gain-additive circuits, in my experience. I particularly found this to be the case with an old 90s Fulldrive II I was gigging during that period; and even with all of the voicing/compression options of the FDII, the difference of 18V vs. 9V was what was needed to cut the live mix in that particular situation.

    Your question is about ODs, but I'd like to say as well that I have always favored delays with additional headroom.
     
  10. RyanJH

    RyanJH Tele-Meister

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    I'm no electronics engineer, but here's my simpleton understanding of it.

    Consider we're feeding our transistor/opamp with half supply voltage (4.5V with a 9V supply, 9V with an 18V supply). This allows the voltage to swing equally in both directions, meaning that it will clip at both extremes equally.

    Assume the initial pick attack through a medium output humbucker is ~1V, which quickly drops to less than 100mV as the note decays.

    Assume the transistor/IC has a gain of let's say, 10.

    This means that the device is going to take that 1V initial input and try to swing it 10V.

    With a 9V supply we get clipping of those 1V peaks, since the device is trying to produce a higher voltage than our supply can provide.

    With an 18V supply, we get no clipping (but wait, don't we Want clipping in an overdrive/distortion pedal?). This is where dynamic range comes in.

    This clean but much hotter (higher output voltage) stage can push the following stages into clipping, but you can control how much with your picking dynamics, or volume control.

    You're using a small voltage (your guitar's output) to control a bigger voltage (the transistor/opamp output). Where else does this principle apply? Tube amps. The small (1V peak) voltage from your guitar on the grid controls the large (200-400V) voltage on the plate.

    Basically, with a lower supply voltage, you're probably clipping right from the start. With a higher supply voltage, you've got an initial clean stage that lets you decide if it clips the next stage or not.

    /End uneducated explanation

    To those who know what they're talking about (Read: 11G), please correct me if I've absolutely butchered this.
     
  11. DaveKS

    DaveKS Friend of Leo's

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    A easy way to demo what higher voltage does is to play with other end of the spectrum, starving a pedal of voltage.
    [​IMG]

    This end of the power philosophy gives a very poignant example of how voltage applies to a pedals performance, where as when you increase voltage the effect is more subtle as you increase it, cutting voltage to 7.5v you'll hear dynamic range wane, you'll hear harmonic overtones shift into more odd order rather than smoother even order ones. Beyond the dynamic and higher headroom aspects already mentioned, harmonic overtones usually shift a little more to even order side as you go up in voltage with a pedal, making them sound and perform in a more amp-like fashion for lack of a better word to describe it.

    There are few fuzz pedals out there which have voltage starve trim pots built in and it's very easy to hear what varying the voltage does to them.
     
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