Have I figured out the amperage properly?

[ZaO]

Hey guys. I just got a pair of these: http://uk.yamaha.com/en/products/mus...s7/?mode=model

Even though the output power is 95W, the power consumption is apparently 55W. So I work it out by the latter yeh? I worked it out to be around 0.22-0.23 Amps per speaker. But in either case, 0.5 Amp fuses would be the right things to use on these speakers, right?

I just want to make sure I don't put in a fuse which could allow too much through. I would cry if I broke these speakers!

Cheers

[Domestic_Ginger]

P=IV
I=P/V
0.23=55/240

But 0.5*240=120W just to get you worried

[scaryjim]

If the speaker doesn't have an internal fuse or circuit to protect against over-current, I'd be amazed. Plug fuses are really just a belt-and-braces last line in case a really huge spike comes down the line. Any company worth their salt aren't going to rely on an end user putting the right fuse in the external plug to protect the very expensive components they've put in their high-end powered speakers. If you get the kind of surge that's going to blow the plug fuse it's going to blow a 3A just as quickly as a 0.5A.

55W is likely to be an averaged power draw, and you'd be upset if your music got to a loud bit and your speakers suddenly went dead because their peak power draw is actually 150W....

[peterb]

Pretty much as Scaryjim said - the fuse in the plug is primarily to protect the mains cable - from the plug to the unit being powered. So the fuse in the plug top should not exceed the current carrying capacity of that mains lead. In practice common sizes are 2, 3, 5 and 13 amps.

In some cases, mainly domestic appliances like kettles, the plug top fuse also protects if the appliance fails. for things like amplifiers where there may be a switch on surge, having a fuses with too low a rating may cause it to fail prematurely because of this.

Your amplifier should have an internal fuse to help protect the speakers and electronics should a fault develop. The amplifier will not be 10% efficient, so it will take more power than the stated output power. The units of output power are also misleading though - the most accurate/representative is RMS power - the most misleading is peak music power - anything that is quoted as Peak music power almost certainly falls` into the 'cheap 'n' nasty" category. You may also find that power output or power capability is quoted at a certain percentage of thd - or total harmonic distortion. At higher power outputs, this figure rises.

But to come back to your original question, a 3 or 5 amp fuse in the plug top should be fine.

[watercooled]

Just a word about fuses in general, you really want to be using approved BS1362 fuses in plug-tops, and not replace it with something like a glass fuse which could cause more problems. BS1362 fuses have a fairly high breaking capacity; they should both survive fairly low-impedance shorts without exploding, and prevent an arc from being drawn which would defeat the purpose of having a fuse.

Assuming the OP means plug-top fuses, then the appliance will only draw what it needs, so under normal conditions the fuse shouldn't make any difference. The fuse should only blow to prevent further problems under fault conditions e.g prevent a fire if a faulty lead shorts out. This type of fuse doesn't actually break immediately upon reaching its rating, and the breaking time will vary depending on the amount of overcurrent, hence you get graphs for fuses showing response time vs current.

OTOH if you mean a fuse between an amp and the speaker to prevent damage caused by over-driving the speakers, then it's a different matter and one I'm not so sure about. However considering they apparently have internal amps, I'd expect the MFR would include circuit-protection fuses internally for this purpose.

[ZaO]

wow. thanks for all the detailed replies guys! i don't understand everything that was said tbh :/

but here's the situation. i ordered these speakers from germany. they use what i normally call "kettle leads" to power them. they came with the euro 2-pin style mains leads. as far as i can tell, you can't even take these mains leads apart to put a fuse in them! but the shop was kind enough to bundle in a couple of uk mains leads for free they put 13a fuses in these leads (most likely just the standard fuse these cables have in them). now i know that the speakers will have their own protection in them. but i like to try and get the right fuse for mains plugs so that a surge will hopefully be stopped before it reaches the device.

the lowest fuses i have are 3 amp (BS1362). so i've put them in the plugs. you reckon i'll be good with them? if not, i can go out and find some other fuses tomorrow thanks again. the help is awesome!

[kalniel]

the lowest fuses i have are 3 amp (BS1362). so i've put them in the plugs. you reckon i'll be good with them? if not, i can go out and find some other fuses tomorrow thanks again. the help is awesome!

Yes, that's fine. If you want to protect from surges though, use a surge protector.

[ZaO]

Yes, that's fine. If you want to protect from surges though, use a surge protector.

yes i shall put them on one of those too! thanks