What’s the fuse rating for the P20?

The 120 VAC US version, that is.

UK, the fuse for a P20 is a 5 amp 250 volt 5 x 20mm slow blow

US, a 6.3 amp 5x20mm 250v slow blow.


Thanks Elk!

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So are folks who are using the SR Orange, using the actual spec value for their fuses? I’m hesitant to go up to an 8A rated fuse for the P20 when it’s designed for a 6.3A. For the DACs and transports I’ve read that a lot of Orange users go up to the next size.

I guess one way of looking at this, is if the orange fuses are not correctly marked, then if you get the bigger marked value in reality the real world value is what you are trying to achieve.

Also what I don’t get is the UK fuse rating of 5A is no where near enough for 2000VA output, let alone the input

I don’t get either, LOL. My power amp uses a bigger fuse than the power plant that feeds it :thinking: I Let the engineers worry about it.

I guess it can’t be used like a standard fuse for mains in, But for an internal circuit.

PowerPlants and amplifiers have capacitors and can output greater than their input.

(The fuse is on the input, not output.)

Just going to add…for short amounts of time. This fits music but no way the P20 is rated for a continuous load to 2000W. That’s why the fuse sizes don’t work like expected. I’m not going to run my toaster off my P20. Bet it would make killer toast for a little while….

One last twist, by the National Electrical Code (NEC), a continuous electrical load is one that lasts for 3 hours or more. Lighting is a great example. Lots of special considerations kick in at 3 hours.


I know what happens to my 71 year old bladder at 3 hours but what happens electrically?

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The typical over current device (circuit breaker or fuse) is sized to handle 80% of a full load. You have to derate continuous load for the over current device. There are 100% rated over current devises but they get big and robust as you go up in current. A 2000A bolted pressure fuse is a big f…er fused switch.

I’ve been told that “audiophile” fuses are typically missing in-rush capacity; standard commercial fuses have it.
If that’s true, then are standard commercial fuses under rated?

I wouldn’t call it under rated. Continue loads are fairly rare as a total of the loads and require more robust parts so rules were written to deal with the practical situation. What’s hard to explain is that fuses and circuit breaks don’t hit their limit and then trip, it’s an asymptoticly decaying curve of current v time. There are lots of different ways to handle that with different over current device types.

Never ever say “asymptoticly decaying” to a person of my age.


Yes, but not continuously, they can’t generate power. Using your logic, 5 x 250 x 0.8 ( for output efficiency) = 1000VA continuous output max for P20 output. That is not right

Of course, I assumed this was understood, along with my reference to capacitors. @amsco15 additionally already added “for short amounts of time” for those who needed clarification.

I am sorry this was unclear.

I know that my Conrad Johnson CA200 integrated can be problematic because of in-rush when it goes from standby to on when using aftermarket fuses. It uses a 6.3A slow-blow for the mains input and bear in mind the CA200 is basically one-half of the CJ 350 amp.

For a while I switched to the Hi-Fi Tuning Gold XLT fuse which is an extra slow-blow design specifically made for problems that may be caused by in-rush. In terms of sound, however I preferred the HFT Silver Star and that’s what I use now. My workaround to using the Silver Star is to leave the CA200 on all the time. And when the amp does go into standby because of a power interruption, I never, ever power it back on really early in the morning when there’s hardly anyone on the grid. So far that’s worked fine.

I know this doesn’t really answer your question but I’ve just had 3 cups of coffee. :coffee:

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