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OT: Schematic for DIY 3.5mm audio switch box

Discussion in 'Burnt Fingers DIY Effects' started by Armchair Bronco, Dec 28, 2009.

  1. Armchair Bronco

    Armchair Bronco Tele-Meister

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    I'd like to build a simple 3.5mm audio A/B switch box housed in something like an Altoids can. I want to use a DPDT switch and three 3.5mm stereo jacks -- 2 inputs and one output.

    How do I wire this up? I found a company that sells these, but they want $24 + shipping. Figure I can do it myself for under $10...something like this:

    [​IMG]

    The instructables website also has an article, but the photos aren't detailed enough and there's no schematic.
     
  2. Armchair Bronco

    Armchair Bronco Tele-Meister

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    On the Harmony-Central site, someone suggested I should use a 3PDT switch instead to eliminate popping sounds when switching circuits. I think I'll go that way instead.
     
  3. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    OT? If you mean a transformer isolated ABY box, it'll cost you more than $10.
     
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  5. Armchair Bronco

    Armchair Bronco Tele-Meister

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    Not sure what you mean. I just need to build an A/B switchbox to take output from my computer ("A") and output from my small 19" HDTV ("B") and let both sources share a single set of Boston Acoustics computer speakers.

    Anyway, even if I have to spend $20 on this, I'd rather go the DIY route than spend the same amount of cash on a ready-made switchbox. I haven't built anything in a few months, so this will be a fun project.
     
  6. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Cool.

    I thought you were referring to an ABY box for guitar...
     
  7. Armchair Bronco

    Armchair Bronco Tele-Meister

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    Here are some additional details on this. Still need someone to tell me how to wire this up correctly. I want to build a simple A/B audio switchbox that has two 3.5mm stereo inputs and a single 3.5mm stereo output. Obviously, for my needs I'll be using *either* A or B but never both at the same time.

    I want to use a small enclosure and 3PDT switch from Small Bear and use three 3.5mm stereo jacks from Mouser.com

    Here are the parts I plan to use:

    3PDT toggle switch:
    [​IMG]

    Hammond 1590A enclosure:
    [​IMG]

    3.5mm Stereo connector (three of 'em):
    [​IMG]

    So: how do I wire this up? Let's say that the 3PDT switch has the following contacts:

    Code:
    1 --- 2 --- 3  
    4 --- 5 --- 6  
    7 --- 8 --- 9 
    And let's say that the three 3.5mm stereo jacks each have contacts labeled:

    Code:
    G (for ground)
    R (for ring)
    T (for tip)
    Finally, let's say that two input jacks are labeled "1" and "2", respectively, and the output jack is labeled "X".

    So, we have:

    Code:
    1G, 1R, 1T
    2G, 2R, 2T
    XG, XR, XT
    Can someone please tell me how each of the jacks should be connected to the switch? Thanks!
     
  8. Armchair Bronco

    Armchair Bronco Tele-Meister

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    Solved. Someone over at OffsetGuitars.com just posted this for me:

    [​IMG]
     
  9. eyd84

    eyd84 TDPRI Member

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    The switch has to be a 3PDT switch. If you take a look at it behind the switch there should be 9 terminals. When it's all said and done there should be 9 wires attached to the switch. Got it? Good. This is important.

    For those of you out there with a voltmeter you may want to meter it out before you even begin to solder. This will guarantee yourself what terminals provide a closed circuit. The potential to provide current is there and finding out what terminals would or could be open is a plus. In other words you'll touch the terminal that is located in the center with one lead and with the other lead touch either the terminal to the right or the left the voltmeter will beep so what does this really mean?

    The middle row or column what have you is always on no matter the position of the switch i.e. moving the switch to the left or right. This means the middle row will be labeled output. This is where I plug in my speaker wire. The ps3 and the computer in conjunction with a set of brand new Audioengine A5's make use of this 3.5mm switch. Is this beginning to make sense? I hope so.

    Every part but the 3PDT switch I purchased at radio shack. I found the 3PDT switch for $3.00 at a local electronic store. From start to finish this took me no more than 45 minutes and total cost less than $15.00. Ask friends if they have a soldering tool to borrow. Anyway the mount jack I bought at radio shack contains three terminals and if the package reads phone jack this is okay. The mount jack I bought at radio shack was labeled phone jack and it works just fine. A male jack can be broken into parts; tip, ring, and sleeve. This relates to left, right, and ground thus three terminals.

    What I'm about to explain next is really important. If you don't follow these directions carefully the switch will not work. Take into account the arrangement of what wire goes where. When the first row is soldered to the jack terminal repeat for the second row in the same orientation. Take note what terminal on the jack is soldered to what terminal is on the switch. The first row must duplicate itself to the second row with separate set of wires for all three mount jacks. Oh did I tell you you need three mount jacks? You need three mount jacks.

    Let me put it this way. This is to provide a representation for a practical purpose. Pick a terminal on the jack. Solder the wire to the terminal on the jack then solder this wire to the switch terminal at the bottom left this means for the next jack you have to solder the same terminal but different jack then solder to the switch terminal middle left. I'll see if I can upload a picture. Please don't pay $40.00 for a switch when you can save a lot of money by making one yourself. Set aside an hour or two on a weekend and just do it. I say an hour or two because you actually have to go out and purchase the parts so you either need to google a local electronic shop and make the drive which means it could either a 20 minute drive or more. It's instant gratification when you're finished making the switch and finally connecting it to your speakers or whatever figuring out that it works. If it doesn't work then it's not instant gratification it's just put on hold because you'll figure it out. This is a simple project anyone can do. You just have to put in a little effort.
     
    Last edited: Mar 7, 2010
  10. eyd84

    eyd84 TDPRI Member

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    [​IMG]

    Notice the first row of the switch is connected to separate jacks but are the same in regards to what jack terminal is attached. This is what I want to emphasize when it comes to making one of these things. The terminal that is soldered from the switch to the mount jack is arbitrary. You don't have to follow these schematics exactly but if you do you have a good chance making this thing work granted everything else is done correctly but however if you don't follow this diagram just make sure the orientation remains the same. I'll take the extra time to make another picture with color so it would be easier to translate what goes where if I get a lot of traffic. I'll make the picture better if a lot of people get confused looking at this picture. Good luck.
     
    Last edited: Mar 7, 2010
  11. eyd84

    eyd84 TDPRI Member

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    Last edited: Mar 7, 2010
  12. theorymatt

    theorymatt TDPRI Member

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    thanks for posting this. I had asked how to build this kind of selector but I didn't explain it very well. I will be building this this weekend, only using 1/4 jacks for a guitar pedal. Thanks again!
     
  13. theorymatt

    theorymatt TDPRI Member

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    Could someone explain the differing diagrams above? The second with the 3PDT is self explanatory, but what about the first diagram with the DPDT switch with all grounds connected? will both work, but one is inherently better than the other for some reason...?
     
  14. eyd84

    eyd84 TDPRI Member

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    Glad to help. I'm not quite sure if Armchair Bronco's schematics work. I haven't built one the way he's mentioned how to build one. I can tell you I have an ear for sound and this was a concern in terms of using a switch. Much like using a splitter for cable there are some decibels that happen to lose its way ultimately compromising some frequency but after listening to music with the switch I can't hear any difference in the quality of sound whatsoever. ;)
     
  15. eyd84

    eyd84 TDPRI Member

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    Why can't I edit the post instead repost? What I want to do is rectify that last paragraph. At least this way it doesn't contradict the pic. :)

    Let me put it this way. This is to provide a representation for a practical purpose. Pick a terminal on the jack. Solder the wire to the terminal on the jack then solder this wire to the switch terminal at the bottom left this means for the next jack you have to solder the same terminal but different jack then solder to the switch terminal bottom center. I'll see if I can upload a picture...
     
  16. Schiz0

    Schiz0 TDPRI Member

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    Why exactly is the 3PDT switch required?
    Since what i had already in the garage was the type of switch that Armchair posted, i tried it and that way works, however I get a noticable amount of noise. Is this because of the type of switch I used or the type of wires I used?
     
  17. Mumphrey

    Mumphrey Banned

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    This wasn't off-topic as far as I can tell. Seems to be what "Burnt Fingers"
    is about.

    I think as long as it somehow relates to soldering and guitar electronics, you're okay.
     
  18. ibobunot

    ibobunot Poster Extraordinaire

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  19. eyd84

    eyd84 TDPRI Member

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    I've empirically tested Armchair Bronco's schematics before I even posted instructables.com. I'll explain my experience as to why this 3PDT switch works for me. This is totally worth it. You save at least $30.00 doing it yourself.

    Once the switch-box was built I plugged it in my Ipod Touch. The sound was absurd. Naturally I presumed it was incompetence due to my average dexterity more than anything else. I was wrong. Every wire was where it needed to go and the soldering was adequate. More research online concluded in my final decision to replace the switch with a 3PDT. Imagine stepping out the door with your morning coffee in hand, steam bellowing from your cup. The scent is fresh and off to the horizon the view is good but visible only twenty-five feet away. The view is tolerable but unattractive. Now imagine yourself replacing the switch with 3PDT. Just do it. The view is excellent.

    Objectively the sound is distorted and incomprehensible before the switch was replaced. I've read it works for others but simply it just didn't work for me. Hope this helps.
     
    Last edited: May 31, 2010
  20. Schiz0

    Schiz0 TDPRI Member

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    No offense, but no that did not help at all.
    Because you said it was important, I assumed you had actual backed up reasons to why it was neccesary, and thus wanted to know what it was.
    You say you had research conducted online that influenced your decision. Did this research reveal technical explainations, or was it just alot of unhelpful (to me) "i did it this way, it works!" forum posts?
    I don't doubt it works, I just wanted to know WHY it worked better than the other kind, so i'd know if it was something I actually needed to spend money/time on, or if I could just keep tinkering.
     
  21. eyd84

    eyd84 TDPRI Member

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    Thanks for the reply. Please let me explain. A TRS connector also called 3.5mm jack if you're interested take a closer view of this jack reveals there are three divided sections namely tip, ring, and sleeve. This corresponds to its characteristics left, right, and ground which at first I thought all I needed was a 2PDT switch because I had a speaker that sat to the left of the computer monitor and a speaker that sat to the right of the computer monitor so to solder to ground I didn't know if it would do anything but more importantly why I would need to solder ground.

    Some background information the speakers came with a 3.5mm audio wire which makes sense because they were intended to plug into my computer. Armchair Bronco's diagram completely registered in my mind this could work because his diagram shows a switch servicing the left and right speaker. Yes it looks like ground is being shared but unfortunately I think this is the problem in my case. Apparently it works for others I have read testimony his diagrams prove to be effective so this isn't a pejorative attempt to say the least to do nothing but articulate the events to the best of my knowledge what I have observed. On a side note for the sake of experiment I've tried just soldering the left and right wires on the jack mount leaving ground out of the system, this proved to be unsuccessful.

    Since my contingency plan went off course and after some research off the internet I've learned that a 3PDT switch means triple pole double throw and upon viewing the mount jack there were three terminals so it made sense to me to purchase the switch and hope for the best. It worked.

    In short, I'm someone who gives the benefit of the doubt. I already mentioned there were testaments his diagram works so I'll leave it that. It didn't work for me but perhaps that doesn't mean it doesn't work for anyone be it as it may. Hope this helps.
     
    Last edited: Jun 3, 2010
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