Problem with large load from hifi power amp

ruaneg · 24-01-2017 08:22PM #1

Hiya!

I'm got a hifi system with a number of components that use lots of power. Specifically a 200w power amp and a pre amplifier. If I turn them on at the same time the trip switch goes, and i lose power. So I have to turn them on one by one.

Thats grand, but I want to add some automation and use a smart plug to turn it on. I could get lots of smart plugs and try and do a delay using software I guess, but I'd love to get a practical solution. Is it possible to just upgrade a fuse to a higher amperage/load?

I don't really know what I'm talking about, would really appreciate some pointers!

Cheers!
Gary

colm_mcm · 24-01-2017 09:30PM

If you're tripping a breaker, upgrading a fuse isn't going to do anything.

24-01-2017 09:51PM

Hi Gary, can you post a picture of the device that is tripping and I may be able to assist?

ptogher14 · 24-01-2017 09:53PM

The in rush current of them all switching on together is tripping them. It would be possible to build a small device with a couple of time delay relays to help the problem. Another option, if you don't need them portable would be hard wire them to a fused spur unit. This way you could put them on a suitable breaker on the board

24-01-2017 11:07PM

I doubt that the MCB is tripping, 200 W is a small load for a socket outlet (the average kettle is 3000 W). Edit: Unless the amplifier is faulty!
A photo would confirm what device is tripping.

I would suspect that it is the RCD that is tripping. If this is the case the solution would be to put the socket circuit concerned on a dedicated RCD.

ruaneg · 26-01-2017 10:49AM

Thanks for the replies!

It's definitely something with the power amplifier. I had a 400w amp before this one and it didn't cause the problem.

Should I attach a picture of the back of the amp?

Cheers!

deandean · 26-01-2017 11:07AM

Those large power amplifiers can have a massive inrush current.

You possibly have a B-curve MCB installed. e.g. is the legend on the MCB 'B20'?

If you were to get this changed to a C-curve MCB ( e.g. 'C20'), this handles a higher inrush current and probably would not trip.

Best of luck.

ruaneg · 26-01-2017 02:32PM

This is the amp, not it's powering 6ft tall speakers that are very power hungry. So as you guys are saying there is no doubt a rush of current. Its in a Cabinet so it's difficult to take a real world photo.

ruaneg · 26-01-2017 02:35PM

And the fuse board...(probably got the name of that wrong!)

ruaneg · 26-01-2017 02:37PM

Better quality pic... B20 e61

26-01-2017 03:18PM

ruaneg wrote: »

Better quality pic... B20 e61

Ok, I was wrong. It appears to be an MCB that is tripping.
I would guess that the amplifier is faulty.
Although it would have an inrush current I would not expect the current to be of sufficient magnitude to trip a 20 amp B type MCB.

The fact that it is supplying 6 foot speakers is not relevant as the connected load is 200 watts. Or is it? Perhaps the Load is 2000 W (2 kW) ??

deandean · 26-01-2017 05:44PM

I had a huge amp like that about 20 years ago, a Realistic IIRC. It weighted about 30kg and most of that weight is from the enormous power suppy comoonents. The room light used to dim for a fraction of a second when I turned it on!
More modern amps, but not all, have 'soft start' to limit inrush current.

Steve · 26-01-2017 07:12PM

It's inrush, would bet on it. You need a C or D rated MCB.

26-01-2017 07:48PM

Steve wrote: »

It's inrush, would bet on it. You need a C or D rated MCB.

You reckon?
I have a larger amp, Marantz NR1606. It is 250 W and I have no issues with anything tripping.

Steve · 26-01-2017 08:13PM

2011 wrote: »

You reckon?
I have a larger amp, Marantz NR1606. It is 250 W and I have no issues with anything tripping.

My experience is it depends on the power supply - Switch-mode psu's tend to trip RCD's wheras traffo based psu's tend to trip mcb's. I only have experience in panel building and that's what I base my answer on.

whizbang · 27-01-2017 12:36AM

If thats a BEHRINGER A500 then its known for having a large inrush current. I believe there's info on the web somewhere about building a soft-start circuit for it.

ED E · 28-01-2017 10:51PM

whizbang wrote: »

If thats a BEHRINGER A500

The image 100% is. From its Amazon listing. Thats a 2x 300W not a 200W though so not sure if the OP posted the wrong image. Spec: 3.6A(230VAC, 50Hz)

I know bigger PA amps (2KW) often do a self/loop test for 1-2s on powerup before powering on the amp channels. Not sure how this is done electrically but maybe thats causing the inrush?

whizbang · 31-01-2017 01:09AM

Softstarts are usually just a resistor inline with the mains supply to the main transformer. Bypassed with a relay on a 2 sec timer.

ruaneg · 31-01-2017 10:45AM

From the spec on the page where i bought it, it states:

2x 185 Watt RMS @ 4 Ohms, 2x 125 Watt RMS@ 8 Ohms
https://www.thomann.de/ie/behringer_a500_studioendstufe.htm

Im using big Magnepan planar speakers that probable use around 4/5 Ohms on average I believe.

ruaneg · 31-01-2017 10:46AM

thanks Whizbang! thats fantastic, Ill do some googling on soft-start circuits:)

Bruthal · 31-01-2017 11:45AM

I remember a local shop a few years ago, after a power cut, MCB supplying 4 freezer units would trip when reset due to all 4 trying to start compresors at the same instant. Plugging 3 out then reset, plug back in one at a time and no problem. During g normal operation they will never try to start compressors at same instant.

Problem with large load from hifi power amp

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