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Topic # 239570 24-Jul-2018 10:20
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Hi all,

 

I have purchased LG sound bar SK5Y from US.

 

The main unit is 100-240v, 50-60hz which is fine to use with an adapter, however the sub woofer come with it says 110v only.

 

 

 

From the manual:

 

Impedance: 3 Ω

 

Rated Input Power: 200W RMS

 

Max Input Power: 400W RMS

 

 

 

Is this requires a step down to use or can I just plug this in?

 

If so, what wattage of step down should I be looking at?

 

 

 

Many thanks!


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Banana?
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  Reply # 2061578 24-Jul-2018 10:35
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Definitely needs a stepdown if it does not say 100-240V (or similar).

 

You will release the magic smoke if you plug it in.


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  Reply # 2061628 24-Jul-2018 11:31
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From the internet, looks like the sub consumes 33w power, so 50-100w stepdown to be safe?


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  Reply # 2061641 24-Jul-2018 12:02
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Look for the power consumption label on the subwoofer (not RMS), double that, and you should be good to go.

 

 





I reject your reality and substitute my own. - Adam Savage
 


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  Reply # 2061801 24-Jul-2018 16:44
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nickb800:

 

From the internet, looks like the sub consumes 33w power, so 50-100w stepdown to be safe?

 

 

How can a sub with claimed 200W rms output consume 33W max/0.5W standby?

 

(Yeah - I checked the specs and that's what LG claim. What a p!ss-take.)

 

It's class D amp apparently, which are very efficient of course, but it's probably a "30W RMS" sub - not a 200W sub.


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  Reply # 2062531 25-Jul-2018 19:20
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Fred99:

nickb800:


From the internet, looks like the sub consumes 33w power, so 50-100w stepdown to be safe?



How can a sub with claimed 200W rms output consume 33W max/0.5W standby?


(Yeah - I checked the specs and that's what LG claim. What a p!ss-take.)


It's class D amp apparently, which are very efficient of course, but it's probably a "30W RMS" sub - not a 200W sub.



They make the claim based on the amplifier only outputting the claimed power for a very short time. I still think that those claims are still completely misleading though.

Then they sometimes measure the power output with the amp way over driven. (crazy high distortion).





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  Reply # 2062548 25-Jul-2018 20:08
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Output wattage is not equal to input wattage at different voltages.

A 5 volt 1 amp rated dc power supply will mean a rating of 5 watts

It’s not going to consume 5 Watts nor 1 amp of your 230 volt mains.

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  Reply # 2062572 25-Jul-2018 20:42
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MadEngineer: Output wattage is not equal to input wattage at different voltages.

A 5 volt 1 amp rated dc power supply will mean a rating of 5 watts

It’s not going to consume 5 Watts nor 1 amp of your 230 volt mains.


Mad indeed.

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  Reply # 2062666 25-Jul-2018 22:38
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MadEngineer: Output wattage is not equal to input wattage at different voltages.

A 5 volt 1 amp rated dc power supply will mean a rating of 5 watts

It’s not going to consume 5 Watts nor 1 amp of your 230 volt mains.

 

Actually - it shouldn't consume much more than 5 watts, switchmode PSUs and even transformers are very efficient.


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  Reply # 2062668 25-Jul-2018 22:41
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Aredwood:

They make the claim based on the amplifier only outputting the claimed power for a very short time. I still think that those claims are still completely misleading though.

Then they sometimes measure the power output with the amp way over driven. (crazy high distortion).

 

It's nuts all right.  The "very short time" wouldn't be more than a fraction of a second of a low E note on a bass guitar.


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  Reply # 2062708 25-Jul-2018 23:22
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MadEngineer: Output wattage is not equal to input wattage at different voltages.

A 5 volt 1 amp rated dc power supply will mean a rating of 5 watts

It’s not going to consume 5 Watts nor 1 amp of your 230 volt mains.

 

My understanding is, (and I haven't done any of this for years so I may be rusty - please correct if wrong),

 

If it's rated at 33W, it's 33W (P=IV). For AC, assuming rms values, sine wave, and 100% power factor. I say sine wave, but, if true rms values (and not lookup based on pp voltage with an assumption of sine wave), that shouldn't matter.

 

The current for a given wattage will differ for different voltage. If the current is the same, the wattage will increase if the voltage increases.

 

33w for 5 V would be 6.6A

 

for a 240V rms supply, that would be only 137.5mA, still 33W.

 

There will be conversion losses if you change voltage.

 

For a 200W rms subwoofer, you would have to be able to supply 200W continuously.

 

I could see it having 200w pmpo (peak momentary power output) by having capacitors charge up and be able to supply the current for these brief periods, however, if it needs to supply 200w continuously, it would have to draw a lot more than what it supposedly does based on earlier replies (I haven't seen the supwoofer specs).

 

For the soundbar, I see on amazon that they say that the output of the dc power supply is 25VDC at 1.52A which would be 38W. Losses would reduce the output from that - 100% efficiency is *somewhat* hard to achieve...

 

 


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