Series/SC-inside/Parallel/SC-outside/ indi-pup control--whew!

Discussion in 'G&L Bass Forum' started by fender3x, Jul 30, 2009.

  1. fender3x


    Mar 12, 2006
    Here's my attempt at the holy grail.

    This mod starts with DavePlayBass's (DPB) Series/SC-inside/Parallel, but makes a few changes. First, it eliminates the pup-selector switch. This is replaced with a stacked, concentric volume pot. No need to switch pups on or off. Just roll the vol up, down or off for each pup individually or together.

    DPB's mod replaces the stock 2-way 4PDT switch with a 3-way 4PDT switch. This mod replaces the the 2-way 4PDT switch with with two 3-way DPDT switches. One goes where the pup selector switch used to be. This one works like the top half of DPB's switch and controls the neck pup. The 2nd goes where the old S/P switch was. This one works like the bottom half of DPB's switch and controls the bridge pup.

    Other than that, I have tried to be faithful to DPB's diagram.

    There are a couple of other items however that are worth mentioning. I had to change the tone circuit path because of the additional volume control. Stock wiring goes from the pup selector switch to treble pot to bass pot to volume. My mod requires the the volume pots to come first, since they replace the pup selector switch. So, this is wired...


    My mod also replaces the stock Bass pot with a push-pull pot. With the pups in parallel, and the push-pull in the "up" position, this adds an SC-outside setting.

    Two other itty bitty changes to stock...

    There's a cap on the stock vol pot. I eliminated that.

    I added a resistor between the tone circuit and the pre-amp.

    The reason for those two changes have been discussed elsewhere...

    So, now that I have drawn it, and gone through it several times with a pencil, I thought I'd post it (a) to see if anybody finds something wrong with it and (b) for use by anyone else who'd like to try it.


    Couple of conventions to note... I don't have a great drawing program, so solder-posts are denoted by a black dot. All solder connections are at a black dot, except for connections that are grounded to pot housings, which are denoted by a green dot with a "down" arrow.

    Caps are orange footballs with the value noted.

    Resistors are pink circles with the values noted.

    All wiring colors are as close to stock as I could keep them...with one exception. used a blue (rather than white) wire between the state-selector switches and the volume pots. There are no blue wires in original G&L wiring. This was just to avoid confusing the white wire from the pups with the "out" wire to the tone circuit.

    OK, if anyone finds an error, I'll correct it and put up a new diagram--thanks in advance to anyone who does.

    If no one does, hope this is helpful to somebody ;-)

    This owes a huge debt to the meticulous wiring diagrams created by Ken Baker, and DPB's mod documents. Also to Ken, Dave, Jim and all the others who have patiently answered my questions in other threads.
  2. spideyjg

    spideyjg Supporting Member

    Mar 19, 2006
    San Diego
    My brain hurts. :D

    Nice diagram of your beast. Ummm how does it sound?

  3. fender3x


    Mar 12, 2006
    Good question! Won't know until I actually do it. Wanted to get it diagrammed before doing it...and vetted by the experts such as yourself. You think your brain hurts! ;-)
  4. My head hurts too! Looks good though!

    There are a couple things I'd recommend:

    1. Because you've spec'd ON-ON-ON coil switches, wiring to the diagram so that operation makes sense "on the bass" will depend on the orientation of the switch. For this reason, it's helpful to specify how the shank keyway is oriented. It's a minor niggle, but helpful in the end for those that don't have the switch pinout. This is easily done with an arrow and notation.

    2. Grounding in a G&L L series is a rather large pain when the stock preamp is used. Consequently, the various ground leads are hooked up wherever it's convenient. In a lot of cases, this means soldered to a pot's can or a terminal strip on the can (or God only knows where else). If the cavity has shielding paint the pot frames should be at pretty much the same potential, but I wouldn't trust it. If you're using the factory pots, the terminal strips will already be there and you'll have to rely on the flexibility of the person reading your diagram to use them. To be safe, I'd recommend making a notation that the pot cans should be connected together with a ground lead/strap and that this strap be connected to the jack's sleeve lug.

    That's a bunch of work you've done, and it's much appreciated.

    Thanks also for the kind words!

  5. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Denver, CO
    Very similar to my L2000, except that I sacrificed the inside single coils option on mine. I have gone back and forth between insides and outsides, and doubt I would really end up using both on a regular basis (especially considering that the switching limits the use of the second single coil option to only single coil- meaning putting either of the pickup coil switches in anything other than parallel with the bass pot pulled will just kill the sound from that pickup).
    I changed my treble control to a push/ pull- I don't think they make reverse-log taper 1meg pots in push/pull form to replace the bass control do they? I have another non-G&L bass wired with a similar bass cut using a normal log taper pot, and it cuts the majority of the bass in the 1st quarter turn of the pot the reverse-log pots like G&L uses are pretty rare birds!). Anyway, my push/pull changes the "single coil with bass boost" as seen in your diagram as "series" with actual "series" setting- ie no capacitors coming off the coil switches.
    I also recently removed the preamp from mine- I never used it, and have taken to leaving the battery out anyway. I plan to try a redeemer in there eventually just for the hell of it. I usually use a Sadowsky outboard pre anyway, so its not likely to matter much...

    You might consider changing the values of the volume pots and/or the treble pot though- adding the second volume control changes the loading of the whole system (it will sound somewhat darker), so using 500Ks for the volumes or a 500K for the treble control will help balance that out some (I chose to use 500K on all 3 in my L2000).

    Good mods though, I'm sure you will love it! Naturally (if you're anything like me), you will probably find 2-4 favorite settings and not really fuss with much else! I actually have been getting more mileage out of the different tones possible from different volume knob settings between the 2 pickups than coil changes recently- usually leaving the pickups in either single coil or single w/ bass boost.

  6. fender3x


    Mar 12, 2006
    Dude! I just realized that I did not credit you above... You were the first person I encountered who had used a stacked vol controls. AND the first person I encountered whose mods control both pups independently. Without your posts I would never have figured out how to get all four "states" and independent pup states without drilling new holes. Thanks for chiming in!

    Reverse log taper? The one meg pot on this page is the one I got:

    It says it's a 1 meg audio taper with a solid shaft. I guess that means I may end up with the problem you mention. Rats!

    I just wrote to the guys at Alpha Products since they seem to make most of the push-pull pots that people use. I asked if they make a 1 meg reverse log taper pot...or if one can be ordered.

    If not, is there a work-around? Can resistors be added or something?

    Do you use both settings?

    Did that--I am pretty sure it was at your suggestion that I got a stacked CTS 500K/500K concentric pot. Probably should have noted it on the diagram....

    I figure it'll be nice to have the options, even if you don't use them much--especially given how difficult it is to try out the settings in a real-world sort of way ahead of time.
  7. fender3x


    Mar 12, 2006
    Good suggestions!

    Will update the graphic at some point. I have put the switch in the diagram exactly the way it orients, viewed from the bottom.

    For now, though, thinking of the "0" as posts on the bottom of the switch...

    0-0 0
    0-0 0 switch toward bridge = Parallel

    0-0 0
    0 0-0 switch in middle = SC inside

    0 0-0
    0 0-0 switch toward neck = series

    Mine's not shielded well so I plan do do that when everything is out of there.

    Stock wiring is a birdsnest, and not really improved by my diagram, which seems to cause headaches (so it's not just me afterall ;-)

    I tried to do what you suggested, but it's still confusing...basically I just left it the way it is done "stock." Jack ground to the treb pot housing. Treb pot housing to the vol pot housing and the bass pot housing. Bass pot housing to the bridge. In my diagram all grounds (except for the battery!) should connect to one of the three green dots...and from the treb pot to the jack.

    Part of the confusion is that in stock wiring, sometimes grounds are green and sometimes they are black...and then there is the fact that one of the black wires coming off the bass pot is not a ground... I think this could be simplified, but I just tried to stay as close to stock as possible.

    BTW, I did one more mod which is not on here...actually the only one that is done at this time. I put in a battery box. This makes it easy to pop the battery completely out for when I don't want to use it--which, like Sunbeast, is most of the time for me.
  8. Yup - the green and black grounds are confusing. Again, this is a product of the G&L preamp. The preamp, switches, and pots are pre-wired outside of the cavity. Then they're dropped into place and the final connections are made. Any extra wires needed are added and those are just one color, and I think that's black. Anyway, it all adds to the confusion.

    A full re-wire to either passive or a different preamp can be useful to fix the issue, but it's a long way to go just for that reason.

    VERY COOL!!! We gotta see picture of the finished product. I'd like to see where you ended up putting it.

    Thanks for all your hard work!

  9. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Denver, CO
    I honestly had never even heard of the reverse log taper until I tried to put a similar bass cut in my Darkstar'd bass and noticed the difference in the taper. It seems like it is used for volume controls in some amplifiers, but I've never seen it used in another inner-guitar context. I also can't comment on how the 1 meg audio put will compare- it may fare better than the pot I used, which is really still useable, just a little tougher to control than the reverse log pot in my L2000 (it goes from full bass to most bass cut in a very small turn).

  10. fender3x


    Mar 12, 2006
    I don't cut the bass much...but your posts have made me think...and order a couple of parts. I found some CTS pots that have STSP push-pull switches. I ordered a couple of those, and I ordered a bass pot from G&L. I don't know if it's possible to switch out the wafers, but it'll cost me less than $20 to try. If I use two STSP switches (say, on the treb and the bass pots), I might get individual control for the outside SC mod... May not work, but I'll report back in any case.
  11. fender3x


    Mar 12, 2006
    Did a bit of research...and if there is a reverse log taper 1 meg pot with a push pull switch out there, I have not found it!

    Given the chart above, the easiest way to do the mod would be to put an audio taper 250K push pull pot in the treb spot, instead of putting a push-pull on the bass slot. I can only find split shaft, but that's no biggie. Call that option #1.

    Aahh! But there are other options, if I can do the wafer swap... Assuming I can do that, I could...

    ...make a concentric pot for both tone controls. All the pots would remain CTS and the proper values. Where the bass pot is I could put a three position DPDT swtich (like all the other). This would give me what a two position switch gives, plus the option of putting the neck pup in outside-SC, while leaving the bridge pickup with parallel/SC-inside/serial options. Call that option #2.

    ...Or, I can "make" two CTS pots with the proper values that have STSP push pull switches. This would allow me to put each pup in "normal" or "outside SC" mode individually. The only downside to this is that switch "up" would be "normal" mode and switch "down" would be "SC-outside" mode. That's fine, but a bit counter-intuitive. A tad easier to get confused in the heat of battle. Call this option #3.

    Assuming all options are possible...which would you do?

    Please feel free to comment if you think I'm going off the deep end ;-)
  12. millahh


    Sep 20, 2005
    Would it be possible to make a reverse taper 1 meg pot by simply flipping the wafer over? I haven't dissected one, so I don't know if the wafers have a native directionality.
  13. Based on pots I've taken apart over the years, no. The wafer itself is an insulating material, such as epoxy or phenolic resin board. The resistive compound is applied to the wafer on one side and the wiper only contacts the compound on that one side.

  14. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Denver, CO
    There are a couple online discussions about adding a resistor across the outsides of a linear taper pot to give it reverse log characteristics, but I don't know what value would work...If I were you, I'd just leave the bass control as is (or take the wafer out of the current one and put it in a concentric pot with the treble control as you mentioned), and do the push/pull with the treble control- works great on my L2000, and didn't require any further modifications apart from purchasing the 500K ohm push/pull pot.

    I wouldn't tell you that you're going overboard necessarily, but I know in my situation that the control that I have is plenty for me without the addition of the extra single coil orientation switch(es). If I did want to do that, I'd put it in place of the active/passive switch (which I never use, as I have a Sadowsky Outboard pre that simply does it better).

  15. fender3x


    Mar 12, 2006
    I think I will try the latter. I have a spare concentric pot, and have a proper 1 meg pot on order from GL... Have been curious about doing the wafer-switch.

    I toyed with the idea of just doing the inside coil setting...perhaps that would be enough... I as about to just do the push-pull pot as you suggested... but today I was cruising by my favorite electronic parts store and found a 4 position, three pole, rotary switch...which is about the size of a normal CTS pot. With that I think I will have Indide, outside, series and parallel settings for each pup individually AND the controls will look the same from the front, except there will be two concentric pots. I should be able to operate the rotary switch with the the standard G&L chrome knob.
  16. I was just reviewing and plotting and planning.

    There is no need to be concerned about orientation for the switches used here. They pinout the same regardless of how they're oriented.

    Please disregard my previous. Guess I was being overly cautious.