Relay to turn amps on - Someone please double-check me

Discussion in 'Archived Threads 2001-2004' started by Michael_Hml, Nov 19, 2002.

  1. Michael_Hml

    Michael_Hml Stunt Coordinator

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    I'm 99.99% sure I calculated this correctly, but I guess I'm just looking for a second opinion before I go and hook this all up.

    I've got a pair of Audisource Amp Two amps that need remote turn-on. They have signal-sensing auto power, but I'm finding that during movies when there isn't much activity in the side or rear surround channels, one or both of the amps will shut down.

    So, my idea was to add a relay turn-on to a power strip, then plug the amps into that and run a 12v control line from my pre/pro to the relay. The issue with that, is the 12v out on my pre/pro is a max of 50mA, and all of the power relays I've been able to find with a 15A rating have a coil load of more than 50mA. That left two options, either use dual relays, an external power source and step up to a larger power relay to control the power strip, or go to a smaller relay for the strip.

    I found a miniature power relay that has a 30mA 12vdc coil and is rated at 10A/120VAC at RatShack - catalog # 275-248.

    According to the back panels, each amp draws 350w - so at 700w for the pair, am I correct in calculating that the load comes out to a bit under 6A and this relay should be sufficient to handle this?

    Also, it's got PCB contacts on it - should I be concerned about soldering 12g stranded wire (from the AC cord on the power strip) directly to the leads without a PCB?

    Overall, is this the right way to go, or should I really just do this with two relays/external power and use a larger main relay with spade terminals?

    Thanks for any advice.

    -Mike
     
  2. Will Orth

    Will Orth Stunt Coordinator

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    Well what i would do is probally get a buddy or if you know how to do this, is get a switching transistor then use that to turn on a bosch relay- those do about 30-40 amp's and you wont have any problems.

    As the
    30mA 12vdc coil and is rated at 10A/120VAC at RatShack - catalog # 275-248. may burn out as you said you needed a 15 amp rating.

    Next I would look to a electronics-audio guru in your area as they may have somthing like that ready for you on hand as i see these items all the time in the surplus catalogs.
    Will
     
  3. Michael_Hml

    Michael_Hml Stunt Coordinator

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    Will,

    Thanks for the reply!

    The only reason I was specifically looking for a 15A relay was to ensure that the relay matched the full capacity of the power strip.

    If my calculations are correct (which is one of the things I'm questioning), I think I'm within the 10A load rating of that relay (assuming, of course that I'm reading all the specs on it correctly :).

    -Mike
     
  4. Mats Kellberg

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    You may experience a rather short lifespan of the relay - due to the amps having large transformers (i.e. an inductive load). What I would do is look for relays rated for both resistive and inductive loads, for example the rating might look something like this; 120V~/15(6)A.
    Which basically means it can handle inductive loads up to an approximate equivalent of 60A resistive.

    Good luck

    Mats Kellberg
     
  5. Wayne A. Pflughaupt

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    Michael,

    I got the impression from your initial post that the problem was the amps are shutting down during long quiet passages. How is powering the amps remotely via relays going to eliminate this situation?

    I’m probably missing something here…

    Regards,
    Wayne A. Pflughaupt
     
  6. Michael_Hml

    Michael_Hml Stunt Coordinator

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    Wayne,

    If I turn off the "auto power" feature on the amps and just leave the power on, I can then switch them with a relay from the AC line.

    -Mike
     
  7. Wayne A. Pflughaupt

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    Got it!

    There are more “elegant” ways to accomplish this (albeit more expensive). Some power conditioners from Panamax and Adcom have switched outlets for amps that can be triggered from the receiver’s switched outlet. And I’ve seen people mention that Sears sells a power strip fairly cheap that can do this as well.

    Regards,
    Wayne A. Pflughaupt
     
  8. Steve Schaps

    Steve Schaps Auditioning

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    I use my DSP A1 switched outlet to turn ON all of my equipment through a relay. It is so easy to do if you can use a switch outlet. That way my amps stay ON no matter what. Rather than use the 12volt output that limits the current available to use multiple relays. One remote command turns everything OFF as well.

    Hope this helps.
    Steve
     
  9. Michael_Hml

    Michael_Hml Stunt Coordinator

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    Wayne,

    Yes, definitely, there are elegant and pre-built ways to go about this. Niles makes products that will do exactly what I'm looking for. I'd prefer to build it myself, though. I think I may have found something at AllElectronics that will work pretty well.


    Steve,

    Unfortunately my Ref50 has no switched outlets, so that's not an option.

    -Mike
     

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