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    power consumption

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    dmagazz

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    power consumption

    Post by dmagazz on Mon Jul 16, 2018 11:38 am

    can someone enlighten me as to what a 200 watt amp(such as the st70) would use as far as electrical watt/power consumption at various levels of loudness? i assume 200 watts is idle with no signal to the output. i know 3 amp fuse and 117 volt, pretty much indicates the protection at 350 watts going by ohms law, so is that to say it will only consume up to 350 watts if i were blasting it full on?
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    peterh

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    Re: power consumption

    Post by peterh on Mon Jul 16, 2018 12:15 pm

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    dmagazz

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    Re: power consumption

    Post by dmagazz on Mon Jul 16, 2018 3:53 pm

    ahhhh. ok, thanks Peterh. so its safe to assume that the 190 watt labeling is basically the full load watt use.
    so then a 3 amp fuse is over rated by at least 45%.
    on the cusp,but i should be ok putting a 2 OR 2.5 amp fuse in there then for added protection.
    ive been getting some voltage fluctuations lately, due im sure from the tornadoes we had a bit ago here in ct, and im thinking there is some collateral power damage that hasn't fully reared its ugly head. i dont want my amp to be subject to stray rebel electrons.lol
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    peterh

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    Re: power consumption

    Post by peterh on Mon Jul 16, 2018 4:10 pm

    dmagazz wrote:ahhhh. ok, thanks Peterh. so its safe to assume that the 190 watt labeling is basically the full load watt use.
    so then a 3 amp fuse is over rated by at least 45%.
    on the cusp,but i should be ok putting a 2 OR 2.5 amp fuse in there then for added protection.
    ive been getting some voltage fluctuations lately, due im sure from the tornadoes we had a bit ago here in ct, and im thinking there is some collateral power damage that hasn't fully reared its ugly head. i dont want my amp to be subject to stray rebel electrons.lol
    One must consider the turn-on surge, that's why 3A slow-blow ( at 110V) is used.
    You shoud consider a device that breaks power when power is interrupted, it has
    been shown several times here ( some kind of ground-fault interrupter with manual
    reset )Maybe that should be a frozen topic on this forum ?
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    sKiZo

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    Re: power consumption

    Post by sKiZo on Mon Jul 16, 2018 5:16 pm

    Yup - manual reset required, so it provides protection against those BLIP BLIP overloads from intermittent power that doesn't provide time for the amp to drain properly.



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    dmagazz

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    Re: power consumption

    Post by dmagazz on Mon Jul 16, 2018 7:28 pm

    yep, i do know of the power on surge.but id wondered if 2.5 is enough for that.and thats a good idea.(the plug in/socket breaker) ive not seen many things that have been discussed. but somehow more often than not when i use the search it comes up dead.
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    PeterCapo

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    Re: power consumption

    Post by PeterCapo on Mon Jul 16, 2018 7:38 pm

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    dmagazz

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    Re: power consumption

    Post by dmagazz on Mon Jul 16, 2018 7:44 pm

    actually, the rack my amp is plugged into has a surge protector and 15 amp push reset breaker in it.
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    sKiZo

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    Re: power consumption

    Post by sKiZo on Mon Jul 16, 2018 7:52 pm

    Big difference between a standard power strip with surge protection and these adapters is the manual reset. If your house blinks and the strip doesn't trip (which it won't) you still get a shiny new slug of power pushed into an amp that hasn't had time to discharge the caps properly. That can reek all sorts of havoc.
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    dmagazz

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    Re: power consumption

    Post by dmagazz on Mon Jul 16, 2018 9:48 pm

    so those trip at just a tweak of currant flux? hmm
    just checked it out actually. didn't realize the link before.
    gfci adaptor. ill pick one up and put it on the main to the rack.
    my harman kardon 730 is rather delicate too.
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    Peter W.

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    Re: power consumption

    Post by Peter W. on Tue Jul 17, 2018 7:32 am

    OK - I will give my patented mini-rant on fusing electronic equipment:

    a) Slow-Blow fuses (those with a spiral-wound element on a small ceramic stick inside) are the invention of the devil, and fit only to protect real-estate, not the equipment they serve. If one reads the specifications on these wretched beasts, they are able to tolerate a 100% overload for 10 seconds, and a 20% overload pretty much indefinitely. So, your 3A fuse will pass 6 A for 10 seconds. And, 3.6 A for as long as it takes to cook a transformer or two.

    b) Yes, tube equipment has a significant starting surge before the filaments heat up - and that surge may be as much as 200% of the standing load.

    c) So, if the standard operating load is 190 watts, and the surge as much as 380 watts for about a second, and one is operating at 120 V at the wallplate, technically, the fuse must be able to take ~3.2A for about a second.

    d) After which, it really only needs to be able to handle about 1.6 A.

    Now, there is something called a Dual Element Fuse. It is able to tolerate very high loads very briefly, such as motor starts and similar applications. These are available in fractional amperage values down to 1/10A and up to whatever. These fuses have the ability to actually protect the equipment where a standard fast-blow fuse big enough to withstand the starting surge, or a conventional slow-blow WILL NOT.  These fuses are expensive, but not relative to a transformer. What happens is that they behave as a slow-blow for the start, then as a conventional fast-blow during operation. NOTE: These fuses  do not like to be short-cycled.

    What I do 'at home' is determine the exact load of the equipment at peak, and then size the fuse to that value. I am running my Vintage 70 on a 2A MDQ fuse.

    https://www.mouser.com/datasheet/2/87/Bus_Elx_DS_2044_MDQ_Series-335854.pdf    


    Note that fuses are wearing parts - and will sometimes blow spontaneously - especially if sized close to the actual load (as they should be).
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    Dave_in_Va

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    Re: power consumption

    Post by Dave_in_Va on Tue Jul 17, 2018 9:33 am

    Peter W,
    Do you know if this would also be the appropriate fuse for a VTA ST 70?

    https://www.mouser.com/datasheet/2/87/Bus_Elx_DS_2044_MDQ_Series-335854.pdf
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    Peter W.

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    Re: power consumption

    Post by Peter W. on Tue Jul 17, 2018 9:55 am

    Dave_in_Va wrote:Peter W,
    Do you know if this would also be the appropriate fuse for a VTA ST 70?

    https://www.mouser.com/datasheet/2/87/Bus_Elx_DS_2044_MDQ_Series-335854.pdf    

    It would, in the correct range. I happen to have an iso-variac with a very fine-pitch ammeter that allows me to get the precise (and accurate) steady-state power draw. And from that, I size fuses.

    https://forums.qrz.com/index.php?attachments/img_9297-jpg.394181/
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    Dave_in_Va

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    Re: power consumption

    Post by Dave_in_Va on Tue Jul 17, 2018 12:55 pm

    So without an "iso-variac with a very fine-pitch ammeter" I can't really tell if the 2 amp MDQ fuse is the one that would work for my VTA 70, right? I'd just be gussing?

    https://www.mouser.com/Search/Refine.aspx?Keyword=2A+MDQ+fuse
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    Peter W.

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    Re: power consumption

    Post by Peter W. on Tue Jul 17, 2018 1:03 pm

    Dave_in_Va wrote:So without an "iso-variac with a very fine-pitch ammeter" I can't really tell if the 2 amp MDQ fuse is the one that would work for my VTA 70, right? I'd just be gussing?

    https://www.mouser.com/Search/Refine.aspx?Keyword=2A+MDQ+fuse

    Do you have a VOM with an AMPS setting? IF you put that in series with your amp and the receptacle - which should be good enough. Hot side, and done with care.

    You can also measure across a fixed resistor and calculate.
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    dmagazz

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    Re: power consumption

    Post by dmagazz on Tue Jul 17, 2018 2:57 pm

    peter,thats exactly what i put in my dynaco. an mdq 2a. i didnt think of the variac + meter thing before, i modded my variac into a small contained unit that give's me live amps and volts out(2 separate meters-both fused). i can plug in my st70 and see EXACTLY how many amps and volts its drawing as its running.

    StevieRay

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    Re: power consumption

    Post by StevieRay on Wed Jul 18, 2018 11:31 am

    Peter W. wrote:OK - I will give my patented mini-rant on fusing electronic equipment:

    a) Slow-Blow fuses (those with a spiral-wound element on a small ceramic stick inside) are the invention of the devil, and fit only to protect real-estate, not the equipment they serve. If one reads the specifications on these wretched beasts, they are able to tolerate a 100% overload for 10 seconds, and a 20% overload pretty much indefinitely. So, your 3A fuse will pass 6 A for 10 seconds. And, 3.6 A for as long as it takes to cook a transformer or two.

    b) Yes, tube equipment has a significant starting surge before the filaments heat up - and that surge may be as much as 200% of the standing load.

    c) So, if the standard operating load is 190 watts, and the surge as much as 380 watts for about a second, and one is operating at 120 V at the wallplate, technically, the fuse must be able to take ~3.2A for about a second.

    d) After which, it really only needs to be able to handle about 1.6 A.

    Now, there is something called a Dual Element Fuse. It is able to tolerate very high loads very briefly, such as motor starts and similar applications. These are available in fractional amperage values down to 1/10A and up to whatever. These fuses have the ability to actually protect the equipment where a standard fast-blow fuse big enough to withstand the starting surge, or a conventional slow-blow WILL NOT.  These fuses are expensive, but not relative to a transformer. What happens is that they behave as a slow-blow for the start, then as a conventional fast-blow during operation. NOTE: These fuses  do not like to be short-cycled.

    What I do 'at home' is determine the exact load of the equipment at peak, and then size the fuse to that value. I am running my Vintage 70 on a 2A MDQ fuse.

    https://www.mouser.com/datasheet/2/87/Bus_Elx_DS_2044_MDQ_Series-335854.pdf    


    Note that fuses are wearing parts - and will sometimes blow spontaneously - especially if sized close to the actual load (as they should be).

    The absolute Gospel Truth.  Amen!
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    dmagazz

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    Re: power consumption

    Post by dmagazz on Wed Jul 18, 2018 4:30 pm

    ok with my variac / DC voltmeter( i divide by.636)to get ac/amp meter, i have a switch on it as well so i can leave the variable  setting and just turn it on, so i turn it on at 100%, it goes to 1.9a, down to .8 amps, warms up and goes to 1.6, i ran it for a couple hours, it stayed 1.6 all the way up to when i started to push it. when the bass gets hard and heavy, the amp meter shows it bump the needle with the bass thumps as expected,but it never went over 1.8. so its safe to say a mdq 2a fuse is right on the cusp when its pushed. i like it Smile
    here is the variac unit i made a couple years back.


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    CletusB

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    Re: power consumption

    Post by CletusB on Sun Aug 12, 2018 10:55 am

    This is what the power-monitor my VTA ST-120 is saying this morning (and this is very typical)
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    dmagazz

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    Re: power consumption

    Post by dmagazz on Sun Aug 12, 2018 2:52 pm

    as id expect, the 120 uses a bit more than my st-70,it doesn't seem to go past 1.8a with a sweet sounding load. im rolling on a safe mdq 2a fuse.

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