will high power trip my fuse?

[bonzo75]

If I have a class A 300w amp, will it trip my power in a London flat if it doubles down to 2400w * 1 ohm? Of course here the class A drops to below 37.5, I think (300/2, 150/2, 75/2)


Assuming normal from the wall power

 

[RogerD]

If I have a class A 300w amp, will it trip my power in a London flat if it doubles down to 2400w * 1 ohm? Of course here the class A drops to below 37.5, I think (300/2, 150/2, 75/2)


Assuming normal from the wall power

I doubt it. The only question I would have are they dedicated lines? I have two monoblocks with 25 amp breakers fed with two 20 amp circuits and have never tripped the line breakers. Though my speakers are about 94 db sensitivity.

 

[Diapason]

If you're using a standard 13A fuse in your plug then you'll be certainly be "close" at a nominal wall voltage of 230V (even though London voltage is often closer to 240) since I=P/V=2400/230=10.4A.

If the amp is actually outputting 2400W into 1 ohm, then the chances are it's sucking a fair bit more than that from the wall as no amps are 100% efficient. So yeah, it probably will blow a fuse in your plug at those levels. Will it trip the fuseboard? Probably not if its a 20A circuit, although I wouldn't be boiling a kettle in your listening room at the same time. FWIW I regularly blew 5A fuses in my power cables with a Krell KSA 80, although that was due to a switch-on surge.

 

[bonzo75]

Well I could get a 30a set up here, if I could get an electrician to do it fuseless.

 

[ddk]

First, how many pure Class A amps do you know?

You can always change your breaker to a higher amperage.

david

 

[RogerD]

Before you would change the size of breaker,consult a electrician. The size of the wiring dictates the limit of the breaker size. In the U.S. #10 wire can be used for a 30 amp breaker

 

[Jazzhead]

Be interested to know which amp you have in mind . 300 w Pure Class A , would be one monster .

 

[Folsom]

If you're using a standard 13A fuse in your plug then you'll be certainly be "close" at a nominal wall voltage of 230V (even though London voltage is often closer to 240) since I=P/V=2400/230=10.4A.

If the amp is actually outputting 2400W into 1 ohm, then the chances are it's sucking a fair bit more than that from the wall as no amps are 100% efficient. So yeah, it probably will blow a fuse in your plug at those levels. Will it trip the fuseboard? Probably not if its a 20A circuit, although I wouldn't be boiling a kettle in your listening room at the same time. FWIW I regularly blew 5A fuses in my power cables with a Krell KSA 80, although that was due to a switch-on surge.

If his amp is putting out 2400w then it's drawing a lot more than that. I'd say it's thermally limited sooooooooooooooooooooooooooooooo far before it hits that much output for more than a blip of whatever juice the capacitors can hold. Class A output can easily be as bad as 1 to 10. That's 1w for 10w spent. It's basically impossible for mortal sized heatsinks to allow that to happen long enough to trip a breaker. Plus his transformer will have a thermal meltdown.

Whatever the manufacturer says your amp is rated at, use that. Any manufacturer worried about tripping a breaker will add a soft-start to the amp since a dead-turn-on is the only time it draws as much current as possible since the caps are all the way drained and thermal limiting isn't an issue.

 

[bonzo75]

Be interested to know which amp you have in mind . 300 w Pure Class A , would be one monster .

Symphonic line Kraft, used. The options in terms of 1 ohm ability and budget are that, Krell old FPB, Gryphon colosseum. All used

 

[GuillaumeB]

Speaking of tripping 13A fuses I never realised this until recently. The standard BS1362 13A fuse will happily conduct 20A of current continuously without tripping and will handle a hell of a lot more for shorter bursts. See here:

http://www.pat-testing-training.net/articles/fuse-operation-characteristics.php

Guillaume

 

[Diapason]

News to me too, Guillaume. I take back my earlier comments.

However, all this has me wondering how I managed to blow fuses in 3 or 4 power cables over the summer. Maybe just as well I no longer have that old Krell!

 

[Speedskater]

A Class 'A' amplifier outputting 2400 audio Watts will require some very large fuses and a large air conditioning system.

Why not get a "Kill-a-Watt" (or similar) AC line meter and measure what's really happening?

 

[ddk]

Symphonic line Kraft, used. The options in terms of 1 ohm ability and budget are that, Krell old FPB, Gryphon colosseum. All used

Of course you know that these amps aren't Pure Class A designs, they operate in Class A only at 8 ohms and it's Class AB at anything less. Given your choice of speakers 4 ohms is already a stretch ! Also given the chassis size and operating temperatures of two of these amps I'm highly suspicious of their 300 watt Class A claims even at 8 ohms, that's why I asked earlier about the amps.

david

 

[bonzo75]

Of course you know that these amps aren't Pure Class A designs, they operate in Class A only at 8 ohms and it's Class AB at anything less. Given your choice of speakers 4 ohms is already a stretch ! Also given the chassis size and operating temperatures of two of these amps I'm highly suspicious of their 300 watt Class A claims even at 8 ohms, that's why I asked earlier about the amps.

david

Yes, which is in my first post I said the class A at 1 ohm will be 37.5, as it keeps halving