Help me mod my pedal!

Discussion in 'Effects [BG]' started by RobinC, Oct 2, 2016.

  1. Hello pedal gurus, hopefully this is in the appropriate forum.

    I want to mod my Loopmaster A/B pedal to accommodate three inputs, one from EB ("A" in the diagram below) and two from DB (B1 and B2), as well as add a second mutable output (Y2) to be controlled by the TUNE switch.

    The background is that I'm now using a recently acquired Krivo magnetic pup on the DB for my stage sound, and only sending the piezo to FOH where the engineer will blend the piezo signal with the pup signal. The problem with just tapping the piezo with a DI and going strait to FOH is that I have no control over muting the signal when I need to tune. I know there are DIs out there with a mute, but most of them seem overkill for what I want to do and more importantly, I'd like to be able to control everything with a single click from the Loopmaster.

    pedal diagram-01.jpg

    My electrical engineering experience consists of basic soldering- if this is a relatively easy mod than I am game to tackle it myself. If it gets complicated, however, I'll probably outsource the work. Really this post is more about "is this possible?" than "how do I do it?" at this point.

    One major question I have is if it will even work to have a phantom-powered DI with a 10 meg-ohm load on one side of the Loopmaster and the piezo pup on the other?

    The pedal currently looks like this:
    True Bypass with Tuner Out and AB Inputs 982005.JPG

    Last edited: Oct 2, 2016
  2. I should also mention that I have not settled on a DI, but have been leaning towards the Radial unit. Other suggestions welcome!
    Last edited: Oct 2, 2016
  3. jez79


    May 2, 2004
    So the green and red paths are already functioning as you want?
    You'd be adding the blue paths/hardware to what's there already?
    You'd run into a problem connecting the blue path with the green and red at the tuner out, all paths connect so you'd send everything out the blue output (Y2)

    I think your best bet would be keep the blue path fully separate, add a pole to your tuner stompswitch (3pdt instead of dpdt, 4pdt instead of 3pdt) and have that extra pole cut the blue path or connect it.
    You don't need the blue path feeding the tuner anyways
  4. Right, the Red and Green paths are the existing A and B, respectively.

    Exactly right.

    So if I understand what you're saying, modify the tuner switch to connect/disconnect Blue. Tuner-off would connect so that Y2 output is engaged, tuner-on would disconnect to cut Y2 output. The tuner itself would never see a signal from Blue, but green is there for tuning the upright anyway.
    Last edited: Oct 2, 2016
  5. jez79


    May 2, 2004
    There will be 6-9 connections on the tuner stompswitch. You'll have to connect everything identical on the new bigger foot switch, and connect your extra jacks to the extra switch poles (three extra switch connections, but you'll only use two, the center and one edge)
  6. Ok, just for fun, would it be possible to add a toggle switch that would allow me to put the Blue path through the fx loop? Open would be just A or B1, closed would be B1 and B2. Or would this have the same issue as connecting the blue path to the tuner output as describe above?
  7. You could add a toggle that would turn on/off a buffered splitter on the blue signal, sending one split to Y2 and the other to the FX loop but the return is going to go to Y1. If you want to keep your piezo out of the amp, then you'd need to resort to a stereo TRS effects loop (jacks and cabling). Tip would be for the regular FX loop, Ring would be for the piezo's loop.

    That's just at the switcher box, at the FX end...

    Your piezo won't be able to use the same effects as the Krivo and EBG (while maintaining separation of piezo from amp). Solutions:
    separate FX just for the piezo,
    stereo effects,

    Some FX don't like having a TRS inserted into them when they're only really capable of TS. So even if you turn off your red/green in the loop, the blue "ring" may not be well accepted by whatever you're plugging it into.

    The splitter (and mixer if required) can be had on DIY PCBs from Fuzz Dog, Musikding, GGG etc, or you can find vero plans at tagboardeffects. Search "Buff n Blend".
  8. Thanks for the detailed response @Feral Feline, that makes sense. Sounds like it's more trouble than it's worth for this project, especially considering I never really use fx on the upright anyway. In the end, if I ever do use fx on the upright, maybe having a wet and dry signal will be a good thing...
  9. I opened up the pedal last night to see what is going on in there. Both the input selector switch and the tuner switch are 3pdt. That means I'd need to replace both of those with 4pdt switches to have an extra set of poles for the new blue path, right?
  10. Post a gut shot?

    Just curious.
    jez79 likes this.
  11. IMG_6068.JPG
  12. In terms of a parts list, I think i'll need two jacks, some wire, and two of these:

    1 x 4PDT Stomp Foot / Pedal Switch Latching - USA Seller - Free Shipping

    What I'm not totally clear on is the wiring. Conceptually I *think* what I have to do is just copy the existing wiring on the 3pdt switches to the new 4pdt switches, and add a path for the piezo (blue) path. This will need to be done on the tuner switch and the input selector switch. My understanding is that the 4pdt switches should come with a wiring diagram, so maybe that will clarify the next steps...
  13. Some 4PDT switches are paired rows of six

    1, 2, 3 — 4, 5, 6
    7, 8, 9 — 10, 11, 12


    Bien sur, most 4PDT switches are four columns of 3.

    1 4 7 10
    2 5 8 11
    3 6 9 12


    Here's a thread about the two 4PDT types, with some "alternative" numbering system.

    Here's the functionality of the two different switches, and you can see how the numbering system I've used works well transferring between them because the pole-groupings share the same exact numbering:


    Ignore position 2 in the above diagram, it's for the middle position of a toggle 4PDT; stompers are on/on, ie positions 1 and 3 in the above diagram.

    Due to space constraints, you may find the 2x6 4PDT better fits some situations, as it is somewhat narrower than the 3x4 4PDT, though it is taller. Looking at your gut shot, I think you'll be fine with the 3x4 4PDT you've selected.

    As you noted, use the first 3 columns as a direct transfer of your 3PDT's wiring, then use the last column as though it were a SPDT. So really, the wiring diagram you need for the blue piezo path is a SPDT diagram.


    I'm no good at drawing up these types of diagrams, the above was the only SPDT diagram I could find, but you've got the basics and can figure out the rest. As Jez79 said, you'll only be using two lugs of the "blue-piezo" pole per switch.

    SUGGESTION! Since you're re-doing the wiring of two of the switches, maybe consider a complete rewiring and COLOUR-CODING all of them. Looking at all those black wires is bloody confusing. There are several DIY online shops that sell multi-coloured hookup-wire sample kits if you can't source it locally. It will make any debugging you may have to do much easier. For me, I keep power to red, ground to black, signal to white and use other colours if-when I need more diversity.

    Like painting, prep is the key. Map out in advance what coloured wires do what; copy the current layout on paper, then lay out your colour version on paper. Then label the wires with masking tape, all before picking up the solder-iron and even then maybe do one wire path at a time. I also like to use shrink tube for bundling of wires all going from one common location to another common location (but I always forget to put the shrink-tubing on before soldering the wire, or leave one wire out of the bundle by mistake :laugh:)

    Also, if you get buzzing issues, maybe consider sending the blue-piezo entirely to ground (*I don't know if that'll work, and of course only do this after checking everywhere else for the source of hum-buzz – cold solder joints, bad power etc). Your project has been educational for me, thanks.

    Do it! FX sound great on DB (IMO): I use reverb, chorus, delay, flanging, even dirt – in most cases I keep it super subtle where you don't really notice it until you turn it off and then realise how much it was adding ), +1 to maintaining a dry signal and sending both wet and dry to FOH.
    Teijo K., RobinC and jez79 like this.
  14. Great feedback, thank you!

    I think I'll order parts tomorrow and get this thing rolling. :thumbsup:
  15. Forgot to thank you for the Gut Shot.

    Thanks! :cool:
    RobinC likes this.
  16. No prob!

    So I went and ordered a pack of 24 gauge wire (multicolored!). Then I noticed that the pedal actually uses 22 gauge wire. D'oh! Will that be problematic?
  17. Ok, I attempted to draw up a wiring tonight. This is with the existing circuit unchanged, just with the addition of the blue path and the new 4pdt switches at TUNE and A/B as discussed above. I can't say I totally understand everything thats going on, but I do feel that it helped.

    In particular, I can't wrap my head around whats happening with the first two sets of poles on the A/B switch. Why are they crossing each other? And whats up with the jumper at the 3rd set of poles at the tune switch?

    pedal diagram2.jpg
    Last edited: Oct 11, 2016
  18. No problemo.

    The skinnier wire is slightly harder to handle while working on the pedal, but is preferred for working in tight spaces when there's not a lot of room inside the pedal. The amount of power going through pedals ... 22 or 24 – neither is going to have a meltdown. Really, you've only got 9v wired up for the LEDs.

    Most DIYers are using 24, from what I've discerned previously researching what to get. I've got some pre-tinned stuff in 24, and picked up some non-tinned 26awg for 1590A builds (would've preferred it tinned but oh well).
  19. I sure wish some of the more experienced solder-jockeys would weigh in here. Oh well, us newbs gotta stick together and help each other out. Hopefully someone will step in and correct me when I'm wrong...

    "I can't wrap my head around whats happening with the first two sets of poles on the A/B switch. Why are they crossing each other?"

    As near as I can tell, and I'm sure I'm not saying anything you haven't already figured out, but sometimes things make sense when said "out loud", so that's what I'm doing to try and have it make sense to me – this crossing of signals on the first two sets of poles is where the actual swap-over happens [all the switching between A/B (EBG/URB respectively) is happening on that second pole]. If you've kept the colour-convention of your previous posts, then the EBG is red and the green is URB... The crossing over of wires is confusing to me as well, but I suspect that whatever's on the bottom of the pole is going to ground in position 3 and vice-versa when in position 2 in the diagram below. I'm guessing the crossovers are just to maintain circuit continuity, maybe it helps with cancelling hum or ???


    So ignore #2 in the diagram again and focus on 1 and 3. According to your diagram, the "up" position is your EBG signal going through (URB "muted") – and the #1 diagram is your URB going through, ergo I think your blue piezo should be attached NOT to lugs 10 & 11, but rather 11 & 12.

    "... whats up with the jumper at the 3rd set of poles at the tune switch?"

    Again, I suppose it's to bleed off signal to ground so you don't get a ghost signal from whichever one is "muted".

    This continues to be a good exercise for me, trying to wrap my brain around it all. However...

    I'll have to come back to this later, I've run out of time and have to go pick up some PCBs from the local BYOC rep! :smug:
  20. Ok, cool. And I assume that it won't be a problem to mix gauges if I leave some of the original 22 gauge?

    Hmm, now that is confusing! I based the position of Blue off of the LED indicators for Red and Green. I was reading it as EB is the "down" position and UB is the "up" position because I figured that when the LED is lit, the corresponding channel is engaged. So wouldn't it make sense that Blue should be on the same side as the Green LED, i.e. the "up" position?