1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

9V vs 18V onboard preamps?

Discussion in 'Pickups & Electronics [BG]' started by organworthyplayer337, Mar 14, 2016.


Tags:
  1. organworthyplayer337

    organworthyplayer337 Professional Hack

    Oct 28, 2014
    Charlotte, NC
    Why do some preamps only run on 9v when others need 2x 9v batteries? My stingray has a 3-band EQ and only requires one 9v. Another bass has a 2-band EQ and needs 18v


    Why is that? And is there any advantage to requiring more volts?
     
  2. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    The vast majority of preamps can run on either 9v or 18v. The only advantage of an 18v preamp is you get more headroom.
     
  3. organworthyplayer337

    organworthyplayer337 Professional Hack

    Oct 28, 2014
    Charlotte, NC
    Excuse my ignorance but what is headroom? I think I have an idea but not completely sure,

    Thanks!
     
  4. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    Same principal as headroom in an amp. You can push it harder with no breakup. Its the reason that when a battery in an active instrument starts dying, the bass starts to sound over driven.
     
  5. 40Hz

    40Hz Supporting Member

    You can also design a circuit to multiply the voltage internally. So just because a pre uses a 9v battery, you can't assume it's also running at 9v.

    And as others have previously mentioned, higher voltage usually equates to better headroom in a properly designed preamp.
     
  6. In general, headroom is the ONLY difference between 9V and 18V operations. 18V would be preferred for maximum headroom, while 9V would be preferred for having fewer batteries.
     
  7. organworthyplayer337

    organworthyplayer337 Professional Hack

    Oct 28, 2014
    Charlotte, NC
    Does headroom affect tone?
     
  8. Will_White

    Will_White

    Jul 1, 2011
    Salem, OR
    Generally no, but taken to the extreme yes, alot of distortion pedals use ICs that are taken beyond what they can cleanly amplify with their given voltage, in this case upping the voltage reduces the amount of distortion, the same applies to onboard pre amps but since they aren't distorted to begin with usually it doesn't do much, it might gve you a little bit extra battery life as the two batteries in series can dip to a lower voltage then just one battery.
     
    organworthyplayer337 likes this.
  9. It depends on how you look at it. Most of the time, it will not. When you hit notes that are loud enough to distort a preamp with lower headroom, then a higher headroom preamp will pass the signal more faithfully. That could be seen as an improvement in tone.
     
  10. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    Only if you run out of it. Personally I never boost a preamp enough to push it into distortion with 9v.
     
    Geri O likes this.
  11. bassbenj

    bassbenj

    Aug 11, 2009
    This is basically it, but there is a design subtlety here I will briefly mention. The signal out of your bass is AC and is centered about ground. That means it goes positive and negative usually a couple volts or so max. If the IC or circuit of a preamp runs off a single battery some way must be found to split that voltage into positive and negative sources. There are a couple ways to deal with this. One is a floating active ground clamped half way between 0 and 9 volts. The other is to just ignore the problem and amplify all signals as positive voltages and then use a capacitor to block the DC and bring the signal down to centered on 0 volts. If you don't quite get all this, it's OK. The point here is that these options require some large and expensive capacitors to work properly at the low frequencies a bass puts out. Manufacturers don't like to use these parts because they cost more money. Hence there is a tendency to cut corners. And these cut corners can negatively affect tone.

    On the other hand, many analog IC chips are designed to run on dual plus and minus supplies. Typically this is what is found inside your amp. So if you just put in two 9 volt batteries wired with a ground between them you can get essentially a plus and minus 9 volt dual supplies and you don't have to deal with the above voltage shifting. This simplifies a lot of things and eliminates the need for large value blocking capacitors. For this reason a preamp designed for dual 9 volt batteries (MIGHT...no guarantees in life) be better than a straight 9 volter.

    Of course if both preamps are properly designed then only difference should be that the dual battery one has more headroom. I can say that for my style of playing even with my super hot MFD pickups I can't recall running into headroom problems, but I'm sure it can occur.
     
  12. lz4005

    lz4005

    Oct 22, 2013
    In talking about preamps it may be easier to think of it as 18v systems sounding less compressed than 9v systems. It's pretty rare to hit an onboard preamp hard enough to really distort it, unless the battery is dying. But to a lot of people, myself included, the difference in sound is like having a small but noticeable amount of compression on the 9v as compared to either an 18v or a passive system. Some people like what that sounds like, some don't. It's one of the reasons people get into passive vs active arguments all the time.
     
    organworthyplayer337 likes this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.