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Review: OLP MM3 - Parallel / Series Mod

Discussion in 'Pickups & Electronics [BG]' started by therealting, Jul 24, 2007.

  1. My OLP 5-string originally came wired with a vol-vol-tone setup, but would tend to hum if the two volume knobs were not set at exactly the same level. This was generally tricky to do, so I pretty much always had them both fully on or fully off.

    I decided to rewire the bass with a single volume and tone, and use a mini-toggle for parallel / split wiring on the humbucker. I ordered a DPDT switch (it was a pack on 5 on eBay), some cloth-covered push-back wire, and they arrived a couple days ago. While I was at it, I decided to get some copper foil to do a full shielding job.

    The soldering in the bass is pretty bad... I'm not very good at soldering myself, but I don't do it very often and certainly not for a living, but I think the wiring is neater now than it was, in spite of the added wires required for the switching.


    I quite like the new look - I replaced the middle pot, so it now has the two knobs on the "outside", with the mini-toggle between them. Plugging in, I found out that the cheap pickup in the OLP had incorrect colour coding, so I was getting phase-cancellation. Switched the wires around, no problem.

    End result - the bass sounds much better than it did! In parallel mode, it sounds just like it did before, except now I have full control over the volume without fumbling or hum. The series mode has a little more volume and has a nice midrangey quality which works well for fingerstyle. I think everyone who owns one of these OLP passive basses should consider this mod... it costs practically nothing and makes the bass much, much more versatile!
    klaymaster likes this.
  2. cash87


    Jun 26, 2006
    Louisville Ky
    I did a little mod to my OLP MM3, just attaching the back pickup wire to the first volume. This made were I only have to use one knob to control the volume.

    I know little to nothing about modding basses, but I think its still in parallel. I would like it to be in series but not sure how that should be wired. I dont care of having a parallel/series switch, I just want it in series. Could you tell me how to do that?
  3. That's easily done:

    First, detach the back pickup wires from the pots.

    Next, locate the two poles where the front pickup wires are attached. Detach one of them, and replace it with one of the wires from the other pickup.

    Finally, attach the two remaining wire ends together (you should have one from each pickup). The pickups are now in series.

    Plug in and see how it sounds. If it sounds thin and tinny, you've probably wired them in reverse phase... in which case you just need to swap around the wire connections for ONE of the pickups.

    I strongly recommend the series/parallel mod though, because you then get two very usable, but different sounds... and DPDT switches are so cheap.
  4. Hey therealting, I was planning on doing the exact same mod to my mm2 four stringer. Do you know of any site that has a wiring diagram for that set up? Thanks.
  5. Thanks for the links, looks like I'll be figuring this one out the hard way. Great job with your bass.

    Since the olp doesn't have the bare wire like in the diagrams, did you just ignore it all together, or did you do something different?
  6. Michael Vee

    Michael Vee Supporting Member

    Feb 3, 2004
    Knoxville, TN
    Yet another option for OLP MM basses is the five-way pickup selector switch from HAS Sound.

    "5-Way Rotary Pickup Selector, Prewired
    For two pickup guitars or 4-wire humbucker
    This prewired rotary switch offers the following pickup configurations:
    Position 1- Neck
    Position 2- Bridge + Neck, Series
    Position 3- Bridge + Neck, Parallel
    Position 4- Bridge + Neck, Series, Out of Phase
    Position 5- Bridge
    All you have to do is hook up your pickups. Can also be used with a 4-lead humbucker to switch between either coil by itself, or both coils in series, parallel or out of phase! Installation instructions included. PLEASE NOTE: Your pickups must have a positive lead and a negative lead to be used with this switch. Pickups with a single conductor plus braid cannot be used. Threaded bushing of the rotary switch is 3/8". Includes black or white chicken head knob. "
  7. I didn't use that part of the diagram. I wired the pickups to the switch as shown in the series/parallel switch diagram, then I took the two outputs from that diagram and connected them to the pickup inputs on the other diagram.

    That rotary switch looks cool... however I wasn't interested in getting either coil by itself because of the hum. The out-of-phase sound is also pretty useless to me, it just sounds hollow and thin... so IMO this mod gives me the two useful sounds from that 5-way mod, with much simpler switching.
  8. Man, I wired my bass up, but something just isn't right. I'm trying to attach the wiring diagram i made of it, so could you check that out and tell me what I did wrong? Thanks for any help.

    *Edit* I'm having trouble resizing it, Sorry for the delay.
  9. basslyon


    Jun 24, 2007
    Melbourne, Australia
    Non fosters drinking alcoholic.
    I've done a similar thing on mine but i replaced the pickup too. It's amazing the versitliy one little switch can add. it's actually almost a worthy stage bass now
  10. Argh, it took me 2 days but I figured out my pickup had incorrect color coding as well. I like the new sound, but I don't really see myself switching to parallel too often. I might just hard wire the pickup into series now.

    After I finished the wiring job, I noticed that my tone knob now works backwards. When I turn the tone knob clockwise it muffles the sound like it should if it's turned counter clockwise. Any idea where I might have gone wrong?
  11. chengann


    Apr 22, 2003
    i just picked up a used olp mm3.
    the "bridge" vol knob works fine.
    the "neck" vol knob seems to have minimal
    effect except a sudden vol cut off.

    is this the phase cancellation you guys mentioned?
    so, i should just swap the wires around
    (the red "hot" wire with the exposed "ground" wire)
  12. LegionHWP


    Aug 24, 2010
    Hot damn! I picked up an OLP MM3 off Craig's list locally for a song this week. Popped on here and decided to try the parallel/series toggle mod. I liked the sound when I turned down vol pot #2 but the hum really bothered me.

    After reading up on the various options (push/pull pots, single/parallel/series combos, etc) I decided I would be happy with losing the 2nd vol pot if it gave me a similar sound with no hum. I'm also more interested in one or two great useable tones that experimenting with every possible option. It's bass after all ;)

    I ended up using a single on/on DPDT toggle and like the poster in this thread took out the 2nd vol and placed the switch in between the vol and tone. Used a Diagram off the Seymour Duncan site but most of the other ones were the same. The only slightly tricky thing was figuring out the color codes since my MM3 PU has two sets of white/black wiring (white is pos, black is neg). Also the output jack has a 2nd ground sleeve wire on the white tip which also needs to be soldered to ground.

    This thread is old but if anyone sees this and would like I'd be happy to draw a diagram of exactly what the wiring should be for a stock OLP MM3. Not sure if there are more than one version of these but again mine had two vol, one tone, and two grounds on the output jack. Both vols were B500k (linear) and I couldn't read what the tone was but I needed up using two B500k pots anyway. Also the tone capacitor was a .1 uf (104) which I found odd since most diagrams and threads seem to mention a .047 or .068 uf. I ended up using a .047 anyway and it's not bad with the two tones I now have although at full off it does tend to be a little muddy and is a subtle change as you roll it on.

    Bottom line I am EXTREMELY pleased with this mod. The one setting is a bit trebly and gets a little woody as you roll down the tone. the other setting is a full round hotter signal and sounds very ballsy (especially on the low E and B). And best of all dead quiet with NO hum at all in all settings. I know a lot of folks upgrade the stock pickup in this but honestly I see no reason to at all now. it sounds *that* good.

    Cost was a few hours time researching, making a mock up with extras parts, and less that $5 in parts and it's like I got a whole new 100% useful bass. Highly recommended and super thanks for the various posts in this forum that made it happen!

  13. BassLife77


    Nov 13, 2009
    San Diego
    I would highly advise to replace the pickups, pots and wires in those OLP's if you are going to add switches. the stock electronics are pretty bad and the PU hums like crazy in single coil mode. if you upgrade the PU you will still get hum but not as bad as the stock one
  14. LegionHWP


    Aug 24, 2010
    Well I did swap the pots and wiring when I added the toggle. By doing the parallel/series on/on mod there is ZERO hum in either position so that solves that.

    I have a handful of great preamps and outboard gear if I want to beef things up so at this point I see no reason to swap out the stock pUp. With the mod it's actually quite useful.

    I WILL be putting some $$ into getting this a pro setup though. The neck and frets are in good shape and feel good but the action could be a lot better.
  15. ERIC31


    Jul 1, 2002
    Maricopa, AZ
    I love my OLP MM3. I'm going to try that mod. Anything that could make it better is ok by me! =)
  16. Legion, I'm glad you resurrected this thread. I have recently fitted an on/on/on switch to the Squier VM Precision (tb pickup) following Darkstrike's thread and am about to work on an OLP MM3; only one vol works properly, the other slightly and the tone not at all.

    My plan is to completely remove the lot and replace with a Warman overwound pup, EMG BTC (concentric), the on/on/on taking a pot hole and a fresh CTS 500k audio vol. I'll update the thread with my results but, if you have time, your diagram would be useful to others and perhaps (if my replacement pup doesn't live up) me, IMO.
  17. I've now wired up the Warman pup to the dpdt and thence onto the EMG BTC, CTS vol and the battery connections. Like the OP, I have EMI copper tape to shield things up. The whole switchover should be pretty soon. With fresh Elixirs as well, I realize a lot of variables have been introduced - there really ought to be an improvement. Still, I haven't spent a lot so I hope someone will find an update of interest.
  18. LegionHWP


    Aug 24, 2010
    Just a quick note to say I'm putting together a diagram and pics so should have something specific in the next week or so to share. Just ordered some new strings so I'll pop it open before dropping it off for a setup.

    Action isn't the best right now but I played it for a few hours using my old' trusty TC electronics bass compressor pedal. I've done a ton of recording direct with that and with the new switch in the OLP both the series and parallel tones are *fantastic* . Looking forward to getting this beast 100%!
  19. LegionHWP


    Aug 24, 2010
    Ok I put together a diagram of what I did on my bass. I'm pretty sure this is what the OP in this thread did. The mod as I'm presenting it removes the 2nd vol pot and uses a single on/on DPDT to switch between parallel and series wiring on the humbucking pickup. This eliminates any hum and gives you two different tones to work with. (You can still use the tone and vol knob on either setting of course.)

    I'm not sure if I'll be able to embed the diagram in this post so I uploaded it to: http://daedsound.com/OLP_MM3_Series_Parallel_Switch_DPDT_mod.jpg as well.

    A few notes:

    The MM3 is stock Fender jazz bass wiring stock. This has two vol (one of each pickup, and one tone. Instead of two single coil pickups the MM3 has two sets of wires from each side of the humbucker. You can use pretty much any standard jazz wiring diagram to see what this looks like.

    The OLP MM3 pickup has two sets of white/black wires. On my diagram I made the white wire orange in color so you can follow it easier. Same wire as the white on your pickups.

    The Green ground line on the diagram is soldered to the top of the vol pot along with the third leg of that pot.

    The first leg on the tone is left empty

    The output wiring from the jack on the bass had two strands on the tip. The center (white) is the signal and is wired as shown on my diagram. The outer is wired to ground. Note sure if all output jacks are like this or not.

    Finally in a previous post I mentioned I used a TC Electronics bass Compressor. My bad, I use a tech 21 bass compactor pedal not a TC. Sounds great on the OLP especially with this mod.


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