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Outboard power supply for active electronics: wattage?

Discussion in 'Pickups & Electronics [BG]' started by Captain_joe6, Jan 22, 2006.

  1. I'm starting to get together a bunch of ideas for the electronics for my next bass (fretted 6), and one thing I really would like to do is be able to run the active electronics from a phantom-powered, balanced XLR cable. The hardware isn't really a big deal, I've got the necessary connections as far as building is concerned. One thing I do need to know, however, is what wattage of power supply I am going to need, and any other specifics that it should have in order to run an 18 (or maybe 27) volt system comprised of one (1) very unique 5-band preamp and pickup select/blend system, three (3) EMG active pickups (bridge to neck: 45J-45TW-45DC), and one (one) piezo bridge system, all capable of running off internal rechargeable batteries or the external power supply, and outputting to XLR, 1/4 (for when you've got to run on battery), and 13-pin MIDI (so I can get individual signals for each string, and then really go wild). Complicated and almost certainly unnecessary, I know, but I really really want it, and would like to do as much of it myself as possible.

    So, to recap: what wattage of power supply should I look for in order to power all that stuff up there at 18 to 27v? What other special characteristics (if any) should I look for? Thanks!
  2. Trevorus


    Oct 18, 2002
    Urbana, IL
    It's not so much wattage, thought you can figure that if you have the amp draw of your electronics. I would say that 200 mA would be more than enough for most circuits. Phantom power would not be the greatest idea, but an external power box would be good. A built in double switch jack that charges the batteries when plugged in to the power supply, then turns everything off when unplugged. Also, it'll need to run normally when plugged in without the external power box.
  3. Exactly what I'm going for, but the battery electronics will be switched on via an actual switch so that I can leave the bass plugged in. And when I said phantom power, I suppose I meant power box. Either way, the body of this thing is going to be huge, but its a sixer, so thats no big surprise. It seems that every time I start reading through the electronics forum I add things too it.
  4. Design/Build your circuits first, then design/build the power supply to suit.
  5. A9X


    Dec 27, 2003
    Sinny, Oztraya
    Make sure you're PS is regulayed as EMG tech help told me that they don't like very much above 27V as an absolute max, so you need to account for turn on/off surges, poor stage power etc. I'd suggest 24V as I've run EMG's off my modified Alembic external PSU.

    The pickups and pre will draw very small currents, lets say (I don't have the specs in front of me but EMG publish them) 0.25 mA per pickup and a couple of mA for the pre for a total of ~3mA. Most linear regulators will hate such a low load, so maybe shunt an amount of current to ground after the regulator via a big power resistor to keep the reg happy. Wastes a couple of watts, but who cares?

    The big advantage I see of having external PSU's is that you're no longer limited to using the absolute crap low voltage and current opamp designs, but, if you have the ability, you can design much, much better sounding circuits. Discrete is my fave, but an NE5532/4 (minimum decent opamp) will sound a whole hell of a lot better than a TL062.
    You can also run +/- rails and get rid of some caps.
  6. Going by the EMG specs of .8 milliamps per pickup (there will be 3 of them), and allowing for, oh, lets say 2.5-3 mA for the preamp, I get a total draw of between 5 and 6 mA. Then the only question mark is how much the 6 piezo saddles in the bridge will suck up. Anybody have any ideas?

    Another idea I've been toying with is using 3 custom-wound (provided they'll do such a thing) Q-tuner BL pickups. I don't know much about running low Z passive pickups versus active EMG's, and how they would each have to interact with the preamp. It was my understanding that an active pickup is just a low impedance passive one, but with more electricity run through it. Am I anywhere close to being right on that one?

    Now, for the power supply, am I going to want a linear supply, or a switching one? If they'd both work, which would be better? I might have a source on a couple (not that I'd need more than one) medical-grade switching power supplies for a decent price, and am wondering if they'd be the thing to go with?

    Now, being no electronics guru myself (but I know a couple of guys who are great with that stuff), what do you all consider the absolute best components to build the preamp with? Dharmabass mentioned that a discreet system is his pick, what does everyone else thing. The basic idea behind the preamp is that I will be able to select and mix signals from 4 pickups, cut or boost the entire frequency range by 12-15 db over 5 bands, and then send it to one of 3 different outputs (XLR, 1/4", 13-pin). Anybody have any other features they think it should have that I haven't already mentioned in this thread? I'd love to hear them!

    Thanks again!
  7. I do believe you're lacking the kitchen sink, a pair of little pull out scissors, a toothpick and a nail file.
  8. Agreed. :p

    Maybe I'll route a power socket to the upper horn and run a gooseneck light from it. Or better yet, I'll take the Rickenbacker 331 "Lightshow" concept and go all out, build a computer-controlled light array into the top using a massive, high-res LCD screen under a sheet of bulletproof glass (just in case), and it will require a custom built computer module to controll it and a fiber optic cable as big around as a quarter to run it all.

    Or I'll just run it to a 1000 watt power source and have a hidden keylock switch to turn all that juice on and off to the strings.


    Seriously, though, I would like very much to take this thing to the outer limits of tonal versatility, power, and quality. Alembic better watch their back. The collective power of TalkBass is nipping at their heels!

    Peace out.