18v vs 9v ?

Discussion in 'Pickups & Electronics [BG]' started by The Unit, Dec 21, 2013.

  1. What is the advantage of a 18v over a 9v preamp in laymans terms?
  2. More headroom I would think. A bit of a cleaner output but someone correct me if I'm wrong.
  3. eddododo

    eddododo Supporting Member

    Apr 7, 2010
    Basically you get more 'headroom' i.e. you can have a larger input spike before distorting/other nastiness.
    Imagine a blind man walking with his can undulating left to right- if the hallway is 9 ft wide he may occasionally smack the wall with his cane (i.e. the waveform), but with an 18 ft wide hallway, he is significantly less likely to tap the wall

    its possible that perhaps there are configurations in which more voltage allows more gain, but I think it is more likely that, again, you get more clean gain before distorting
  4. Randyt

    Randyt RAAPT Custom Wood Productions

    Jul 21, 2010
    Barrie, Canada
    not all on board preamps can do 18V...but you are correct...more headroom.
    outside of that the subtleties are very minimal. (audible)
  5. eddododo

    eddododo Supporting Member

    Apr 7, 2010
    Important point! Definitely don't go and slap in a second 9v without some research!!
  6. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I've tried it and immediately yanked it. I heard no appreciable difference, and the headroom gains didn't impress me at all. So I stick with 9v in my EMG loaded basses.
  7. smperry

    smperry Moderator Staff Member Gold Supporting Member

    Nov 3, 2003
    Bay Area, CA
    Endorsing Artist: Martin Keith Guitars
    moved to pickups and electronics
  8. eddododo

    eddododo Supporting Member

    Apr 7, 2010
    actual preamp EMG's or the 'active pickup passive setup' EMG's?
    mostly just curious, but indeed EMG's are WELL set up to run off of 9v, especially the pickups.
  9. bassbenj


    Aug 11, 2009
    Boomie is right. Increased headroom will be totally un-noticible unless you pickups are VERY hot and you like to "dig in" a lot. A system (like EMG) where the pickup output is matched to voltage levels with 9 volt supply will work just fine and never clip.

    Plus 18 volts does mean two batteries to replace and deal with. Sometimes that can mean double the battery life, but not always. Most preamps keep the current the same when you double the supply voltage so you still have batteries drawing the same current!

    Like Boomie I've done the 18volt thing just for grins and found basically zero difference. Remember that improving the headroom on the bass just lets it put out more output which your amp may not have the headroom for! In fact I've got a bass which came with 18 volts is hot and I always have to plug it into the "active" jack to keep from overloading the amp. So what's the sense? You put in two batteries to boost the output then put it into the "active" jack to pad it back down? exercise in futility.
  10. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Actual preamp EMG's. I have the BQC in two of my basses and a BTS in one.
  11. eddododo

    eddododo Supporting Member

    Apr 7, 2010
    Well... a couple thoughts
    EMG'S likely do fine with 9v because they often NEED gain to be brought up to a more usable level- granted I'm talking about certain models only and only about the pickups, but still, there are absolutely pickups that would clip some 9v preamps. Whether these are good preamps is another discussion..

    Having 18 volts has usually nothing direct to do with output gain.. gain is almost unanimously a product of a feedback resistor/ trimpot in the opamp circuit, or a similar setup. My Roscoe runs 18, and a yamaha junker i have is balls hotter than the Roscoe, even with the gain trimmed full on.

    Whether its worth it is a question of perks, value, and engineering merit; no dOubt there are some 9v setups that are great, but emg's are a unique example for other reasons, and don't forget that headroom in terms of onboard pre's also contribute to NOISE FREE EQ boost, and noise floor in general
  12. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Never noticed any increased noise in my EMG's when boosting at 9 vs 18v. Sure, there's a little, but that's typical of boosting any frequency range, as it boosts its noise floor as well. And since EMG's are the only active systems I even like, I tend to be EMG-centric.

  13. pacojas

    pacojas "FYYA BUN"

    Oct 11, 2009
    tell ya what,.. the EMG's in my Steinberger start clipping at just a hair below 9v! my kid was playing it last week and stated i needed a fresh battery. i didn't notice the distortion at first (i only hear up to 14k). so, i listened very carefully and yes, clipping!
    i was expecting my battery to be maybe 8.5-8.75v, but it more like 8.9!:confused: maybe the bat. in my meter is low, also.
  14. huckleberry1


    Jul 1, 2013
    Mesquite, Texas
    I've got a Fender Jazz V with an 18 volt preamp with Nordstrand split coils and I love it. The batteries just died but I can still play it passively for now. It seems to sound fuller than my other basses but that could be the pickups.
  15. 8.9V is a bit low, depending on the type of battery. Despite the name, new 9V batteries often put out about 9.6V
  16. .
    I love that analogy! :D
  17. okcrum

    okcrum in your chest Supporting Member

    Oct 5, 2009
    Verde Valley, AZ
    RIP Dark Horse strings
    There are also preamps around that use an onboard DC-DC converter to raise a single 9V battery supply to 18-24V for the electronics, so make sure your 9 ain't really a stealth 18...
  18. eddododo

    eddododo Supporting Member

    Apr 7, 2010
    Yea, but i imagine charge pumps would eat up too much current to be practical onboard.. not sure if there are any but it would nt be my first instance of ignorance
  19. RobbieK


    Jun 14, 2003
    I used to work for a large guitar company that has acoustic preamps with two AA batts (3v). The circuit has a charge pump and a voltage invertor, so the circuit sees +/- 6Volts - IOW a 12v circuit. The reason being that two AA's have a higher energy density than a single 9v, plus they are cheaper. They have been doing this for many years.

    The onboard bass pres I design are generally optumised for 9v use. I mostly use discrete transistors instead of the ic opamps that 99% of bass preamp manufactures use, and I'm guessing that a lot of preamps that sound better at 18v is more to do with older hifi opamps that are actually designed to work best at 30-36v. These days there's lots of audio opamps that are designed for low voltage use, probably because of all the usb (5v) and portable digital audio devices around.

    The best way to increase headroom in a pre is to reduce its gain. If your pre has a hifi type opamp, it will almost certainly start sounding pretty average at 7.5 volts. Having two batteries generally means higher battery life, as you can run them right down to 4 or 5v before you start running out of headroom.

    If you like to slap and you run a preamp as well as hot or active pickups, plus you run your onboard bass boost cranked, then I would strongly recommend an 18volt system for most preamps, provided it's within the manufacture's max voltage spec. (I'd also recommend chasing an endorsment from a speaker manufacturer, as you'll be cooking them fairly regularly.)
  20. I had an interesting conversation with a Gent named Means on here who explained to me that if you are running active pickups as well as an active pre, then changing from 9 to 18volts doesn't actually give you more headroom because you are upping the output/headroom of both, so the ratio between them stays the same...

    What he recommends in this situation is running an 18volt system but with the pickups wired off from between the two batteries so that they run at 9volts while the pre gets the full 18, thus allowing you the increased headroom

    And to all those that don't hear any difference between 9 and 18volts, the headroom is much like running an amp with more watts that you aren't really using... Some can hear a difference, some can't, do whatever suits your tastes and ears...