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Guitar Pedal

Discussion in 'General Electronics Discussion' started by Dom G, Feb 25, 2016.

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  1. Dom G

    Dom G

    2
    0
    Feb 25, 2016
    My friend wanted me to build him a pedal. The basic idea of it is to have it be a switch pedal. Two inputs and one output, being able to switch between the two inputs with a 3pdt switch and indicator leds to show which input is hot. I have been struggling to find anything of the sort online or in store. I've got a rough schematic drawn up, but I'm not sure if I have everything correctly pinned out. The picture is attached.
     

    Attached Files:

  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Is his pedal stereo or mono?
    Anyway... if you need indicator LEDs, you will need a power supply. Use batteries, or be ready to fight against noise introduced by an external power supply.
    If you are using a power supply, you can always use a basic switch, and simply use the switch to drive one or more relays instead of finding a 3 pole switch
     
  3. Dom G

    Dom G

    2
    0
    Feb 25, 2016
    The way I have it drawn up, it's using stereo 1/4" jacks, but I can also use 1/4" mono jacks. I started to draw up something that had a dual power source ( battery and external) IMG_0427[1].JPG
     
  4. AnalogKid

    AnalogKid

    2,386
    663
    Jun 10, 2015
    I think the schematic has errors, but it might be that you are assigning switch pins in a non-traditional pattern. The common terminal (Pole) for a DT switch should be in the center between its two closed contacts (Throws). Please redraw the schematic indicating which contacts are the poles, which are throw position #1 (T1) and which are throw position #2 (T2). Also, indicate with arrows the direction of the switch handle movement.

    ak
     
  5. purj

    purj

    47
    7
    Feb 14, 2016
    I built something like this a few years ago. It works, but a big problem is that you get a "pop" noise every time it switches over. I understand there is a method of using a "pull up" or "pull down" resistor to fix this problem, but I've never pursued it. I just live with the pop whenever I play, which isn't often :cool:. Maybe if we get you building yours, someone will also tell us how to fix the pop and we can both benefit.

    I think what @AnalogKid (nice reference, BTW, I love the power trio) is asking for is clarification on the circuit so he knows exactly what you're looking for. Doing this would probably help you sort out your ideas as well. I would suggest that you think about a few points and re-draw your diagram.

    The first point is that the middle set of terminals on the 3PDT switch go back and forth between the outer two sets of terminals, depending on the position of the switch. The way you have it drawn, in one position the top row of terminals will be making a connection between the two (+) terminals of the separate input jacks (which will leave the output silent, except for the "pop" which will initially sound when you click the switch); in the other position this same row will be making a connection between the top input's (+) terminal and the (+) terminal on the output (which seems fine). A better solution might be to connect the output jack's (+) terminal to the middle switch terminal in that first row, and the input jacks' terminals on the switch's outer terminals.

    The second point is that you might use a dual-color LED instead of one which is either lit or dim. This way, the syntax of the display more closely matches an "a OR b" configuration rather than an "on OR off" one. The disadvantage is that the pedal eats up batteries no matter what.

    The third point is that another option would be to use a 9V power supply to drive 4PDT relays (as @AnalogKid mentioned) that switched between the "output" (I write it in quote marks because you can also turn the switch around and use the outputs as inputs, which would be more similar to your intent) jacks and reversed the polarity on the dual-color LED (that's how dual-color LEDs work: reversing the (+) and (-) leads changes the color of the light) all at once. If you're interested in this approach, here's how I have it wired:
    [​IMG]
    Notice that one set of poles goes unused.

    There's one last thing I would mention, and that's about the availability of such a switch in the commercial market. Hit up Google for "guitar A-B switch" and you'll come up with quite a few examples which will not only most likely cost less, but also perform better than your initial prototype is likely to. Of course, this takes away from the pleasure and learning that will come with building your own, so I would suggest that if you do go with the store-bought option, you might also still pursue the homemade path. Making stuff is always fun, and then if you want something custom, such as putting more than one switch in a single box, you can throw two of 'em into a single enclosure (as I did, actually). This would allow you to, for example, switch two guitars between two different sets of pedals on the fly. (Think a little about how this would be done...)

    Good luck!
     
    Angelwood likes this.
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