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Passive/Active/Preamp Questions

Discussion in 'Pickups & Electronics [BG]' started by Nugun, Jan 2, 2012.


  1. Nugun

    Nugun

    Dec 31, 2011
    Mesquite, TX
    Hey all, before I start I already tried the search function and could only find a headache since there wasn't much covering the questions I had.

    I just recently registered here (first post actually :hyper:) even though I've been lurking for awhile. Anyway, I am a senior about to graduate soon and as the first to graduate high school on my fathers side I decided to undergo a custom Warmoth build as a graduation gift to myself ;). Since I have a lot of capital left over from saving up for college (Army ROTC scholarship ftw! :D) I have decided to spare no expenses as this will probably be the only bass I get for a long while.

    Now that that is out of the way, my big issue here is electronics. I am really wanting to go with passive pickups and an active preamp, but I really don't know where to begin to be honest. I want to be able to shift between active and passive with the flip of a switch seeing as I am not ready to make the commitment to immutable active electronics on a bass. I'm also trying to avoid the onboard eq as to not overwhelm myself with knobs and switches and the like.

    My question is would this be doable with passive pickups and an active preamp? How would I go about doing this and what kind of circuitry and electronics would I need to do this? Would there be enough room in a front routed body or would I have to go rear routed? How many control slots would I need to have routed on the front of the body if I'm routing for a side mounted jack? Any help or advice is very much appreciated and welcome.

    P.S. Sorry for such a long post, thought I'd get the introduction out of the way as well. Also expect more questions as I progress on this project. ;)
     
  2. mikezimmerman

    mikezimmerman Supporting Member

    Apr 29, 2001
    Omaha, Nebraska
    Yes, you would definitely be able to use passive pickups and an "active" (there is no other kind) preamp. In fact, that's the way it's normally done, unless you decide you really like the sound of active EMG pickups. You generally start with pickups that have the basic sound you want, then add a preamp--there are lots of prewired preamp harnesses that include all the pots, an active/passive switch, etc.

    However, most preamps include an onboard EQ. If you specifically don't want an onboard EQ, what is it that you're looking for out of a preamp?

    Mike
     
  3. Nugun

    Nugun

    Dec 31, 2011
    Mesquite, TX
    I'm pretty much looking for something to give me that little extra volume without all the extra boost/cut, mids/highs, scoop and score mumbo jumbo that can kinda complicate things pretty quickly. Except I also want to be able to turn it off when it is not really all that necessary. Is there any kind of circuit sorcery that can accommodate a system like this? I'm fairly sure there is, but I'm next to no-good when it comes to the advanced (in my opinion) electronics work when it comes to preamps and the like... Willing to learn though.
     
  4. Lee H

    Lee H

    Nov 30, 2011
    Redding CA
    I have two J basses in which I have added active/passive preamps to dimarzio ultra jazz pickups


    Personal opinion only...right now I am liking the Nordstrand preamp I got from another TBer better than the fender American Standard deluxe preamp, I bought from a fender dealer... but that may be because it is the "new" toy, and I may just be wanting to like it...time will tell
     
  5. mikezimmerman

    mikezimmerman Supporting Member

    Apr 29, 2001
    Omaha, Nebraska
    There aren't a whole lot of boost-only preamps out there that don't also include an EQ, though there are a few.

    What have you been playing up until now? Is there some particular reason you think that you'd need extra volume/boost on an otherwise passive bass, rather than just going for hotter passive pickups?
     
  6. Nugun

    Nugun

    Dec 31, 2011
    Mesquite, TX
    Well as I mentioned earlier I'm heading off to Uni next year (Tarleton State to be exact) and it is known to host a few events (be it tailgate parties or open mic nights) that can get a little on the loud side and I'm just wanting to be prepared for any situation that may arise if I want to get in on that.

    I haven't really owned anything (owned being the key word) really nice myself, but I have had and taken many opportunities to play a lot and suffered an early onset of GAS. That's why my mission here is to create a truly versatile bass. Hence the want of the ability to be able to enable or disable a volume boost at any given moment. I know I might be being over-optimistic but if you shoot for the stars you could hit the moon right?
     
  7. Lee H

    Lee H

    Nov 30, 2011
    Redding CA
    no, what you want is pretty easily attained

    In theory, when an active preamp has adjustments centered, it is bypassed so far as the sound is concerned. . It just gives you more versatility on the instrument. The same thing can be done with a pod, but then you are tied to it. I like the freedom of more on the bass, and a wireless
     
  8. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    When you need to play a loud show, a little volume boost from an onboard preamp IS NOT ENOUGH. That kind of boost is meant for when you want just a skosh more volume during a solo, or to drive your signal along a very long cable. To play a loud venue, you need a loud amp, or good PA support--and neither of those things has anything to do with whether your bass has a preamp onboard.

    Even the quietest passive bass will rock any massive stadium, with the appropriate amp and PA support. Put a preamp in it, and have an inadequate amp or PA, and prepare to feel tiny and weak.

    That said, what you're describing is an active/passive switch, and it is utterly commonplace. Very easy to install, and many active basses come with that feature already.
     
  9. Nugun

    Nugun

    Dec 31, 2011
    Mesquite, TX
    I really do appreciate all the responses. I understand that the matter of volume is left primarily to the amp and PA system, but it is a link in the chain that I would like to be involved. Besides, experimentation on a bass is the only way I'll get anywhere and I figure it couldn't really hurt (I pray I don't live to regret those words).

    I believe Mike Z had stated that there were a few boost-only preamps. Has anyone used any of these and have any recommendations for me to try out? Or if there are any preamps with onboard EQ that anyone here is willing to go to bat for? I figure since you guys have more knowledge than me in the matter, the issue of not having the onboard EQ might seem trivial, but I'm just trying not to overwhelm myself all at once.
     
  10. Lee H

    Lee H

    Nov 30, 2011
    Redding CA
    I think that any of the more reputable companies make good preamps...I personally have Fender, Bartolini and Nordstrand preamps with active/passive switches. I there is nothing I really don't like about any of them
     
  11. Nugun

    Nugun

    Dec 31, 2011
    Mesquite, TX
    How transparent would you say the Nordstrand preamp is? I've heard alot of good things about them, but I want to keep the bass as true to the pickup types as possible. I know there will be some sound shaping but not too much hopefully.
     
  12. Stealth

    Stealth

    Feb 5, 2008
    Zagreb, Croatia
    If you want a no-frills, volume-boost-only preamp, your best bet is to go DIY and assemble either a Tillman FET preamp, a Fender Precision Elite preamp clone, an Alembic Stratoblaster preamp clone, or an AMZ op-amp buffer. All four are relatively simple circuits that don't require that much soldering, each uses a single field-effect (FET) or bipolar junction (BJT) transistor or an op-amp chip, and most have a component that sets the gain (boost), usually a resistor. All pre-amps will give you not only a small to moderate amount of boost, but will also restore the highs you lose whenever you plug in a purely passive bass into an amplifier using a long (10'/3m) cable. I'll explain the circuits a bit.

    The Tillman FET preamp is a is a simple buffer with a small loudness gain (3 dB), made in a FET common drain configuration.

    The Fender Precision Elite preamp is likewise a small buffer with a small loudness gain and some slight tone shaping, made in a BJT common emitter configuration.

    The Alembic Stratoblaster preamp is another common-drain circuit that's somewhat similar to the Tillman, but you have a potentiometer so you can dial in the extra gain.

    The AMZ buffer is one more buffer, but it doesn't use discrete transistors, instead it uses an operational amplifier (op-amp) that's made in inverting op-amp configuration. This one might be a bit more complex to build, and though the default schematic doesn't have gain control, you can add a 1 MΩ potentiometer in series with R2 (the existing 1 MΩ resistor) to get variable gain from 0 dB (no boost) to 3 dB. In fact, while you're at it, check the whole AMZ page - they have a nice page on boosters, and one of those would probably fit into a bass.

    Check around the Internet for details and additional explanations, schematics or circuit boards if these aren't clear. The gain-changing control is usually a potentiometer. Swap that with a trimpot - basically a potentiometer made for rare adjustments, it's physically much smaller and once you're happy with the gain setting you can just leave it as it is.

    You'll also need a two-way switch wired like this that bypasses both the input and the output of the preamp so when you turn the booster off, the preamp circuitry won't still partially be connected to the signal (something that happens in certain pedals, for instance, and sucks at the tone, sometimes massively).

    Switch image courtesy of line6man.
     
  13. Nugun

    Nugun

    Dec 31, 2011
    Mesquite, TX
    I really appreciate all the help guys. Since I want this to come out perfect when I finally do complete all the planning and preparation I don't want to have to rush any of the details before the summer is out.

    With that being said, I think I'm going to give myself more time until I know EXACTLY what it is I would want out of this Warmonstrocity. I probably won't have every detail ironed out for awhile, but that will also give me time to refine my tastes a bit. I'm just gonna keep grooving and picking up information from time to time until I have a crystal clear view of MY dream bass, so for now, the Warmoth project is going to be put on hold.

    Thanks again for all the help guys. :hyper:
     

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