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    Are there any subs for 5AR4

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    pedrocols

    Posts : 62
    Join date : 2014-11-24
    Location : Western MA

    Re: Are there any subs for 5AR4

    Post by pedrocols on Wed Mar 25, 2015 10:35 pm

    Cubdriver wrote:
    sKiZo wrote:PPS ... Bob mentioned the "quick power blip" problem and how it can kill amps. The TDI board gives you a delayed start up and allows the caps to discharge properly instead of creating a destructive surge. Another option - a NON-LATCHING (that's the important part) GFCI adapter ...

    TRC 90033 Shockshield White Portable GFCI Plug with Surge Protection



    The GFCI part isn't important here. Truth be told, that feature probably doesn't even work on a two prong plug - not that I've ever tried a direct short to see what happens. The NON-LATCHING feature means it stays off until you manually reset it. That allows you to let it rest for a couple minutes before restoring power.

    I got mine for around $20 ...

    sKiZ - the GFCI should work with or without a ground connection.  It operates by sensing the current going out and the current coming back, and trips if the difference is more than a few milliamps.  They actually sense by using the two power leads as primary windings for a transformer.  Since during normal operation, I out = I in, the magnetic fields generated by the two wires cancel one another out (same current flowing in opposite directions means equal and opposite magnetic fields which effectively equals NO magnetic field) and there's no voltage output from the transformer.  

    If there's a ground fault, some of the current that's flowing out finds its way to ground through an alternate path - you, for instance.  When that happens, there's less current flowing 'back' through the return conductor, and the magnetic fields generated by each one in the transformer primary no longer cancel completely.  This means that there now IS a magnetic field in the transformer primary, generating a voltage across the secondary which the circuitry in the GFCI senses.  When it exceeds the amount equal to that few milliamp threshold, the device then trips and opens the circuit.

    -Pat
    So does that means is a good solution? Kind of late to ask because I ordered two...

    Cubdriver

    Posts : 68
    Join date : 2014-01-21
    Age : 51
    Location : Southeastern Litchfield Co, CT

    Re: Are there any subs for 5AR4

    Post by Cubdriver on Wed Mar 25, 2015 11:38 pm

    It will certainly help in the event of a brief power glitch.  In that case it acts as a self-latching relay that holds itself closed using the line power. If line power drops out, the contacts open and stay open until manually reset. This will prevent hot starting the amp in a power failure situation.

    -Pat

    ETA - self latching meaning that the power to hold it closed is fed through a set of contacts that are held closed when the relay is powered. If power is lost, when the relay drops out, those contacts open, and prevent the relay from resetting itself when power returns. It must instead be reset by the manual closure of a switch that is in parallel with the now open contacts. As soon as this switch is closed,the relay pulls in and again closes the contacts and the reset switch can then be opened again.


    Last edited by Cubdriver on Wed Mar 25, 2015 11:45 pm; edited 1 time in total (Reason for editing : Clarify description of relay operation)

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Are there any subs for 5AR4

    Post by mantha3 on Thu Mar 26, 2015 7:29 am

    mantha3 wrote:Bob,

    Will a 5U4G from Emission Labs work in an ST120 having only the voltage drop issue?


    http://www.emissionlabs.com/datasheets/EML5U4G.htm

    When you say "the amp WILL lose power" do you mean the Watt Per Channel will be reduced at that is the only issue?

    So do ya think this wold work as a sub?

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Are there any subs for 5AR4

    Post by Bob Latino on Thu Mar 26, 2015 9:22 am

    mantha3 wrote:
    mantha3 wrote:Bob,

    Will a 5U4G from Emission Labs work in an ST120 having only the voltage drop issue?


    http://www.emissionlabs.com/datasheets/EML5U4G.htm

    When you say "the amp WILL lose power" do you mean the Watt Per Channel will be reduced at that is the only issue?

    So do ya think this wold work as a sub?

    Yes - Any 5U4 will work in any VTA amp as a rectifier. The VTA ST-70 has a 5 volt @ 4 amp rectifier line and the VTA ST-120 and M-125's have 5 volt @ 5 amp lines. The loss of power in each amp is slight (maybe 10 %) and most people won't even notice the slight power loss. All the amps will have to be rebiased if you switch to a 5U4 for a rectifier.

    Bob

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