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  1. #1
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    Sep 2010
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    Default Using switched 1/4" jack....switching guitar cab from stereo to mono

    Ok so I never really knew the purpose of a switched 1/4" jack, now I sort of get it.

    I need to make a 2x12 guitar cab stereo/mono switchable just using 2 1/4" jacks. If you plug into one input, both speakers are run in mono, if you plug a jack into both inputs, it will be stereo, left and right. Has to be possible with a switched 1/4" jack, no??

    Or if I even have to use 3 jacks.


    Another use is to provide alternative mono or stereo output facilities on some guitars and electronic organs. This is achieved by using two mono jacks, one for left channel and one for right, and wiring the NC contact on the right channel jack to the tip of the other, to connect the two connector tips together when the right channel output is not in use. This then mixes the signals so that the left channel jack doubles as a mono output.
    Bleh???

  2. #2
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    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    I made a crude drawing of one (also crude) way to accomplish this. It may be just what that quotation you included was trying to describe (it's a little hard to tell).

    Anyhow, what I've drawn is one way to do it, but it's not the best way.

    Mono operation is just fine using this method (plugging into either jack and leaving the other unused). And you can run stereo using this wiring, safely, AS LONG AS the left and right drive signals share the same ground. The jack grounds (hence, speakers) are common in this wiring. So, it will be safest when your drive signals also share a common ground. If you're using a stereo amplifier to drive the cab in stereo, no problem. I wouldn't use separate amps, just to be safe.

    A better (safer) wiring would be to use jacks that have NC switched contacts on both the tip and ring. That would allow you to safely run whatever you like with only minor mods to the wiring I've given.

    Hope this helps!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  3. #3
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    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Hey thanks. Now is the left connection in your drawing one of these switched 1/4" jacks or a stereo jack?

  4. #4
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    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    BTW, My gut feeling on this is that it would just be more reliable to just wire the cab in stereo and make a speaker cable that connects the two jacks in parallel for mono operation. Agreed?

  5. #5

    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Quote Originally Posted by killersoundz View Post
    Hey thanks. Now is the left connection in your drawing one of these switched 1/4" jacks or a stereo jack?
    50 watt head's way is the way to go! I've wired cabs like this myself. As he states, you just need to make sure:
    1.) The lower of the two jacks in the drawing is used for mono. Using just the upper jack will only run the speaker it is connected to, not the lower. Of course you might only want to use one speaker, but to use both in mono, use the lower jack.
    2.) The amp you are using has a common gound for speaker outputs. Most will be okay, except for some "dual mono" setups. Using two individual mono amps could be a problem.

    And yes, you need to use a switched plug, not a TRS. TRS plugs can be used as a "switched" plug in cases where power is supplied on the same ground bus as signal ground. For example, in many effects pedals, the ground lead from the 9v battery (or power supply) is tied into the "ring" terminal of the TRS. Common ground is on the sleeve. When using a mono plug, the ring and sleeve are connected by the mono plug's shaft, completeing the circuit. Same applies for many instuments with active pickups.

  6. #6
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    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Ok thanks!! Now a switched 1/4" jack has 3 contacts??? I didnt know that.

  7. #7

    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Quote Originally Posted by killersoundz View Post
    Ok thanks!! Now a switched 1/4" jack has 3 contacts??? I didnt know that.
    Yes and no.
    There are 3 different types of NC switched jacks. Switched to sleeve, switched to tip, and independent switch.

    You need to make sure the jack you use is switched on the positive lead to follow 50 watt's diagram. These will usually be used in applications where the jack is used for a headphone jack/aux speaker jack, cutting the internal speaker in the process. (Will work differently in your application of course.)

    You could also use the jack that has an independent switch with a minor adjustment to the diagram.

  8. #8
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    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Quote Originally Posted by LSV8 View Post
    Yes and no.
    There are 3 different types of NC switched jacks. Switched to sleeve, switched to tip, and independent switch.

    You need to make sure the jack you use is switched on the positive lead to follow 50 watt's diagram. These will usually be used in applications where the jack is used for a headphone jack/aux speaker jack, cutting the internal speaker in the process. (Will work differently in your application of course.)

    You could also use the jack that has an independent switch with a minor adjustment to the diagram.
    Thanks again, this is coming across far too complicated to me for something that is so simple. I've followed a tube amp schematic easier than this!

    Here are the jacks in question, and I haven't found much actual info on them:


    http://www.parts-express.com/pe/show...number=092-120

    http://www.parts-express.com/pe/show...number=092-118

    http://www.parts-express.com/pe/show...number=092-120

    Oh they say "all contacts switched". Meaning what exactly? God I feel stupid today

  9. #9
    Join Date
    Nov 2006
    Location
    New Hampshire
    Posts
    6,647

    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Use mono switched jacks. Wire the ground always on, connect the switches so that plugging into either jack alone leaves both hots connected, while plugging into both isolates them.

  10. #10
    Join Date
    Jun 2008
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    Arizona
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    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Quote Originally Posted by killersoundz View Post
    Yes, this jack (I'm 98% certain) will work for what you'd like to do.

    I updated the drawing to illustrate true isolated/independent stereo operation. The Rean jack in the link above has NC switched contacts on both tip and ring, and can be used for this wiring (or, for the wiring in my earlier diagram).

    I personally don't like to use plastic jacks in high-current positions (e.g., amp outputs, speaker inputs), but Marshall and plenty of other British-style and boutique people regularly do it and have so for many years. I've never heard any complaints. It's just a personal preference of mine to use open-frame jacks in this position. The Rean part in your link looks very close to the Cliff jacks typically found in guitar amps and gear.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by 50 watt head; 10-30-2010 at 02:58 PM. Reason: forgot to add the drawing

  11. #11

    Default Re: Using switched 1/4" jack....switching guitar cab from stereo to mono

    Quote Originally Posted by killersoundz View Post
    Thanks again, this is coming across far too complicated to me for something that is so simple. I've followed a tube amp schematic easier than this!

    Here are the jacks in question, and I haven't found much actual info on them:


    http://www.parts-express.com/pe/show...number=092-120

    http://www.parts-express.com/pe/show...number=092-118

    http://www.parts-express.com/pe/show...number=092-120

    Oh they say "all contacts switched". Meaning what exactly? God I feel stupid today

    Again, 50's answer above is right on. I'm also not a fan of plastic jacks... but as long as the connections are sound, I suppose it shouldn't heat up much at all...

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