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Experimental passive wirings/pre

Discussion in 'Pickups & Electronics [BG]' started by Frank Martin, Jul 15, 2005.

  1. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    So I'm thinking I'll do some funky uncommon experimental wirings for my upcoming 6.
    Initially I thought about getting Bart 90P46CBC dual coils for some series/parallel/sc goodness, but it looks like I can get LeFay Rough Crystals for almost half price... They are P4 shape, as well, so if I decide I still want to try the Barts, they'll go into my Corvette :smug:

    I'm not really an electronics expert, but luckily my Dad is an electro-engineer and likes experimenting and DIY things, and it looks like I can turn him on this subject, as well :D

    My ideas so far:

    Simple Volume

    Simple Blend

    A switch that bypasses blend and switches the p-ups to series or parallel

    A passive treble-roll-off with a twist: it has selectable freqs.
    The idea came from this article:
    However, I'd build it with a pot and a three-way switch, with the freqs being 2, 3 and 4,5 kHz.

    Output booster. Similar to Villex. Yes, passive.
    My Dad has some ideas how it works. When I first mentioned it to him, some days later he showed me a miniature transformer (a cube about the size of a thumbnail), he said he'll keep looking for a better one, this one is uneven in the lowest freqs.

    So, anyone have any more ideas?
    I'd like to keep this passive, so that's the limit. Oh and I don't want to cram the bass full with knobs *cough* Alembic *cough* :D
  2. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    No responses?

    What do you think about these ideas?

    Any more ideas to add?
  3. fookgub


    Jun 5, 2005
    Houston, TX
    Here are my thoughts:

    The series parallel switch is a neat idea. I use this on two of my guitars, and my MM equipped bass. I find the difference interesting enough to justify all the modes. Remember that with standard blend wiring, your pickups are essentially in parallel. Instead of bypassing the blend completely in series mode, you could switch it so that the lower coil (the one closest to ground) is still connected to its section of the blend pot. This would allow you to "dial in" however much of that pickup you want.

    I don't like the treble roll off idea much. I have tried a two-corner roll off on one of my guitars, and didn't find the difference useful. That said, I'm not fan of those types of tone circuits to begin with - I've removed them completely from many of my instruments. You can try this one out before you start modding. Just build it externally, and experiment with different capacitor values. To me you're sacrificing two holes in your bass to a circuit that's not really all that versatile.

    I've never played much with passive output boosting. Remember that there is no free lunch with these circuits. A transformer will indeed step up the output voltage, but by doing so, you're effectively reducing the load impedance seen by the pickups. This could lead to reduce high frequency response. Honestly, I don't see much point to this mod - your amp has a gain knob, doesn't it?

    My advice is don't do any irreversible mods to one of your good axes unless you *know* you want them. You're talking about 4-5 holes for this setup. Does your axe have 4-5 holes? If it does, then go ahead, but if not, don't drill any holes until you're sure you want this stuff. I've always done my experimenting on cheap instruments, and probably only 10% of the stuff I've tried has ever made it to one of my good axes.

    One other thing to keep in mind is that even mods you like will often have many useless options. I have one guitar that has 50+ switching options. Of those, I use about 5. To me, it's best to try the get the sounds you want with the minimal amount of extras.
  4. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    A reply, at last! :hyper: Thanks!

    That blend/swich idea seems promising. I'll look into it.
    I still think I'll try the vtc with multiple freqs.
    The bass is still under construction (actually, I'm just receiving the parts, and starting the body). First, we'll try these on the workbench with signal generators and scopes and the other things necessary. It'll only go in when everything is tested and works good.
    If this whole passive thing doesn't work out the way I'd like it to, I'll go with something like an Aguilar OBP-3 or a Noll 3-band, and those can take care of the extra holes. :smug: (and it's still better than what Alembics have... :D )
    The output from these p-ups is most probably in the low/medium range (I won't know untill I receive and test them). The auto-trafo will loose some highs, but at least it will bump the output back to normal levels; also, with ceramic p-ups, swamp ash back and ebony fingerboard, I think there'll be enough highs still ;)
    As for keeping it to a comfortable minimum... I think this is about it for me. Of all the controls on my basses, I use the blend (or vols), but rarely touch the active eq. The series/parallel switch should be quite useful from what I've heard; with this project incorporating brighter woods (ash, ebony) and p-ups (ceramics), I think the traditional low-pass tone control can be useful at times. So that only leaves the trafo, but if the p-ups are indeed low output, then it might be necessary. Otherwise, I'd have to go active with this one, too.

    That's about it.
    Thanks for the reply!
  5. fookgub


    Jun 5, 2005
    Houston, TX
    Sounds like you've got a pretty good plan there. I'm still not so sure about the transformer, but I don't see any harm in trying it. Hook it up to a push/pull switch so you can A/B it. My understanding is that ceramic pickups are generally hotter than alnicos, so you may find you don't need the boost.

    Good luck :cool:
  6. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Thanks! (sorry for the delay, I just got back home)
    I'll try the trannie on the bench first, if it is good enough without, then I think I'll leave it out.
    Ceramics I think have higher resonant freqs and therefore more highs, but I'm not sure about them being higher output... I'll find out soon, when this lame postal service delivers my p-ups at last :rolleyes: postal fees from Germany to Hungary for 2 p-ups plus a set of strings, insured was €38 and it's still not here in a week :rolleyes: