about four months ago I bought a JB Systems amp. Very nice amp. Very good build, solid as a rock. Also the Components inside are very high qaulity and thick PCB's

The problem though is when I flick the switch to turn it on, it draws about 3000 watts in the inrush of current, I suppose to feed the massive capictors, but this sometimes blows the fuse which is rated at 13 amp! and even trip an MCB on the household mains supply!!!

Is there a way I can stop this?

Well DON'T go hunting for tin foil , I know you wont but you'd be surprised how many people would!. I am assuming that your switching the Amplifier on independantly rather than with several other items at the same time?

Not a lot you can do really if its tripping the main MCB...especially as it's going to be used from venue to venue (I assume its mobile!). You say its tripping the MCB at home??...in most houses ring main MCB are 32 Amps so I would find it very unusual to be tripping something this high .

Are you sure that there isn't a fault on the unit?, perhaps a slight earth bonding or insulation problem?. If you have access to a PAT tester try a simple test to rule out an underlying leakage / electrical problem.

Switch on surge is common on high powered amplifiers using toroidal transformers although it is rare for it to blow a 13 amp plug fuse, and even rarer to trip an MCB especially that on a ring main.

Once you rule out an amp / electrical problem, there is a way that you can get around the plug fuse blowing, but if you don't know how to do this safetly then consult a qualified electrician

(1) Replace the plug fuse with a standard BS1362 15 Amp plug top fuse. They are rare but obtainable from some electrical suppliers.

(2) Buy a 3 pole mains rated in line holder. These are insulated in line connection fuseholders made for 20mm or 1/4" ceramic fuses. Fit this inline on the mains cable feeding the amplifier as close to the mains plug as possible.

(3) Buy a ceramic 20mm or 1/4" (depending on what fuseholder you bought!) 13A ANTISURGE fuse. These are often used in Microwave ovens so you should get one from a domestic appliance repair centre.

DON'T be tempted to bypass adding the additional fuseholder or try and squeeze the 13A 20mm fuse into a plug top!!, this leaves you open to all sorts of problems.

If you are using the amplifier in a fixed installation, then simply connect it to a 20 Amp switched spur outlet fed from its own MCB in the fusebox / distribution board.

Either way, I get the feeling that all is not well with your Amp, tripping a 32 Amp MCB is not good news,

BTW:- Why the heck do you need an amp that powerful in the first place . If it continues to be a problem on domestic mains, then you may have to resort to using two slightly lower power amps to power each set of speakers.

Hi

Chris, where did you learn all this electrical stuff?

Are you a qualified electrician, cause you certainly seem to know your stuff.

I'm just curious.

Did you go out of your way to get the knowledge because of the work you do, or is it something that you're interested in anyway.

Thanks

Darren

seems very strange. I've never had this problem with amps before. My C-Audio amps dont do it at all.

Whens it's idle it's fine, it does not draw much power at all. When it's powering my speakers it still only draws a small amount of power.

It's just when I first switch it on there is a massive inrush of power either to the two transformers or to the capactors which are huge.

The power rating of the amp is 650watts each side in 4ohms.

Also on this amp I sometimes get electical crackles which can be hard through the speakers. Which must be coming from the mains, noisy mains perhaps?

Earth connections seem fine, checked phase and neutral connections inside whic aslo seem fine.

A 650W x 2 Amp certainly should not be blowing a 13A fuse, even with inrush. I very occasionally use a C-Mark MR series on the mobile which is a 2x 1200W "budget" amp with no special circuitry and i've never had it take out a fuse or trip an MCB out yet!.

It certainly does point to some sort of fault which maybe a minor one, but when coupled with the cold inrush at switch on, is enough to to cause the problem.

Personally i'd take it back to where it came from and ask them to test / replace it. Something doesn't seem right there at all.

It may even be a fault on the soft start circuitry which some Amps have fitted to limit the current inrush or even a winding on a transformer which is breaking down, either way without test equipment you'd be looking for a needle in a haystack.

My advice, take it back and get it checked over.

ok thanks for that Chris.

it's a heavy bugger too at 30kg!

Nice amp though with loads of power.

I have just hooked my amp up with set of speakers

there must be a problem with my amp has it makes pops every ten or so minutes.

What sort of "pops"?? - clicks or thuds? and how often?

just small click every ten minutes. If I dont play any music an let my amp run on silent the clicks are very noticable.

Clicks and pops out of amps is a definite problem, sounds like the main power
transistors are going and I highly suggest you stop using this amp until its fixed.
If you continue to use it you WILL blow your speakers and then do Worse damage
to your amp.

The main cause of clicks and pops is overloading the amp with poor quality Xovers
and too many speakers per channel whereby the ohm stabilty of the amp is
compromised, even with circuit protection ( which is a load of rubbish most of the
time) damage can occur, when loading amps with too many speakers, regardless
of wattage your ohm load goes right down (at times to 1ohm)
Always make sure a amp that can be 2 ohm stable is in real terms 4 ohms loaded
this way you have some margin for safety, I generly prefer to go 1 amp per pair
of speakers and not 2 pairs of speakers per amp as I see in many a setup and it
sounds better.