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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


4 posters

    Speaker AB Switch

    rwbaker
    rwbaker


    Posts : 3
    Join date : 2021-01-20
    Age : 63
    Location : DFW Texas

    Speaker AB Switch Empty Speaker AB Switch

    Post by rwbaker Thu Aug 17, 2023 4:31 pm

    I want to test some speakers with my M125's and therefore need a speaker AB switch. I already know the AB switch is going to impact the sound, but it will give me a relative comparison between my Forte' IIs and Definitive Technology BP9060 speakers. I promise not to leave the switch permanently installed.

    So, my concern is finding a switch that will provide a load to the amps while switching. Does anyone make such a switch? Some have suggested add a resistor between the 8 ohm post and the ground, can this be left permanently? Is there a downside to leaving the resister installed?

    Thanks for any help you can provide,
    Rick
    peterh
    peterh


    Posts : 1861
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Speaker AB Switch Empty Re: Speaker AB Switch

    Post by peterh Fri Aug 18, 2023 5:07 am

    rwbaker wrote:I want to test some speakers with my M125's and therefore need a speaker AB switch.  I already know the AB switch is going to impact the sound, but it will give me a relative comparison between my Forte' IIs and Definitive Technology BP9060 speakers.  I promise not to leave the switch permanently installed.

    So, my concern is finding a switch that will provide a load to the amps while switching.  Does anyone make such a switch?  Some have suggested add a resistor between the 8 ohm post and the ground, can this be left permanently?  Is there a downside to leaving the resister installed?

    Thanks for any help you can provide,
    Rick

    If you want to switch speakers during load you should have a make-before-brake type. This will connect both speakers a short while before disconnecting one.
    Using a switch that breaks-before-make will have the amp unladed for a short while and that might cause flash-over and possibly damage the amp.

    If you insist on using a break-before-make you could solder a 100 ohm resistor between the 16 ohm tap and ground ( and leave it there.)

    Roy Mottram, pedrocols and rwbaker like this post

    Roy Mottram
    Roy Mottram
    Admin


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    Join date : 2008-11-30

    Speaker AB Switch Empty Re: Speaker AB Switch

    Post by Roy Mottram Fri Aug 18, 2023 5:44 pm

    something like this should work fine
    https://www.amazon.com/Monoprice-108231-Speaker-Selector-Control/dp/B007N43T5Y
    to be sure you always have a load on the amp, I would either add a resistor from the 8 or 16 ohm taps to ground (100-220 ohms 2w)
    and make sure at least one pair of speakers is always connected
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    Dale Stevens


    Posts : 203
    Join date : 2014-07-06
    Age : 75
    Location : Loris, SC

    Speaker AB Switch Empty Re: Speaker AB Switch

    Post by Dale Stevens Fri Aug 18, 2023 6:02 pm

    Peter, what wattage for the 100 ohm R ? Dale
    peterh
    peterh


    Posts : 1861
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Speaker AB Switch Empty Re: Speaker AB Switch

    Post by peterh Sat Aug 19, 2023 12:52 am

    Dale Stevens wrote:Peter, what wattage for the 100 ohm R ?   Dale

    5w is ok.

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