Shavano Music Online

    Using Switches Creatively

    6/01 updated 10/03 and 12/03 - Jens Moller - http://www.colomar.com/Shavano/spkr_switch.html
    Here are some quick and simple (as well as fairly common) setups that allow you to select more than one set up. I use these combinations on my speaker systems as needed. Please note: recess the switches so that you don't accidently switch them when you are using the gear (except the Switched Input Selector - you would probably want to be able to switch that one easily).

    The following is a quick refresher on how to hook the female jacks up in the cabinets or cases.


    As used where the + and - appear in the drawings (below)

    		For 1/4 inch (and 1/8 inch) phone jacks, you need to verify which solder tabs go to the + and - connections, 1/4 (and 1/8) inch phone jacks have no standard for which of the solder tabs goes to what. Open cased Jacks are easy to verify - just look at it. In an enclosed Jack, you may need to use a VOM/Digital Multimeter to check which connection goes to what.

    Do not push more than 500 Watts thru a 1/4 inch Phone Jack. If you need more power, look into Bannana Jacks or the Nuetrik Speakon connectors. RCA jacks are really designed for low level signals, not power outputs for amplifiers, however they are used commonly on 25 watt or less power amps. Avoid more than 50 watts running thru an RCA connector of any type.

    The + and - relate to how the speakers are connected. The speaker should have a colored dot on it to indicate + or it will be marked with a +. For Low level audio, the + will be the signal, and the - will be signal ground.

    Here are 2 ways to enable/disable a built in first order cross-over network. This is useful if you sometimes bi-amp your PA setup - You can disable the built in passive cross-over when you are actually using an external active cross-over with seperate power amps. When you need to use them on a simpler system where you need the passive cross-over network, its a simple matter of selecting the mode you want.

    See First Order Cross Over Networks for more information about what the capacitor is used for.

    You would be surprized how well a cheap SPDT switch that is used for house lighting works for this. They are easy to kick on and off with your foot and can be bought at any hardware store (as well as the metal box to mount it all in. Use it to switch inputs to your guitar amplifier or mixer. Simple and handy. If you are using the home wall switches, they will have a 'common' and 2 other connections. Buy a new one for this purpose and remember that the switch ' common' goes to the output. The ground connections all connect together (usually thru the metal case that the switch is mounted in).

    Sometimes it would be nice to be able to select the impedance that your multi-Speaker cabinets operate at. Its not hard to do with a DPDT switch. These examples allow you to select between 4 and 16 ohms in both a 2 speaker and 4 speaker configuration. These only work with the speaker impedances shown. Marshall used a lot of 16 ohm speakers to provide this functionality in some of their 4 speaker cabinets (except they did it with switched jacks - very expensive and not as reliable over time, but certainly possible - Mouser Electronics sells switched 1/4 inch phone jacks).

    Example of translating a DPDT Jack to/from DPDT Switch (Your Switched Jack may be different)

    NOTE: The Ring Connection would be left open for all examples shown above

    A regular DPDT switch will not include NO and NC markings - this is because either position is its normal state. The Switched jack, however, is a momentary contact switch, as as such, when nothing is plugged into it, the NC positions are what it is set to. When you plug a cable into it, the NO positions are what it is set to. Use this logic to figure out what mode you want the Default switch configuration (ie. when nothing is plugged into the jack) when you wire up the jack to the speakers. The NO and NC markings are on the drawing to give you an better cross-reference perspective.

    Be aware that if you use a stereo mode switching jack along with a regular mono phone plug, you have to push the plug in all the way (as you will feel the first detent - about 1/4 of an inch (approx 6 mm) before the jack is plugged in all the way) in order for both the switched connections to end up properly switched.

    Sometimes its nice to be able to switch from Stereo to Mono easily.

    Plug into the Left channel when operating in Mono mode.

    With 8 ohm speakers; In mono mode this will be a 4 ohm load, in stereo mode you will have 2 8 ohm loads.

    With 16 ohm speakers; In mono mode this will be an 8 ohm load, in stereo mode you will have 2 16 ohm loads.

    NOTE: For all DPDT switches shown - I suggest 5 Amp (or higher), 120V rating

    Plug into the Left channel when operating in Mono mode.

    With 8 ohm speakers; In mono mode this will be an 8 ohm load, in stereo mode you will have 2 16 ohm loads.

    With 4 ohm speakers; In mono mode this will be a 4 ohm load, in stereo mode you will have 2 8 ohm loads.

    NOTE: We do not work on Home or Car Audio. We work only with Pro-Audio applications. We cannot help you with Home or Car Audio questions.

    Questions? Comments? .

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