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Old 30th June 2004, 02:11 PM   #1
benny is offline benny  Australia
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Default help - loud pops from my amp causing me pain in the rear end

Hi All,

I have a problem with my amps. every time anything electrical is turned on/off in our house... there is a sudden loud pop... most noticeable through my subwoofer which is loud enough pop to make me really feel it, but the other speakers pop too.

it happens in the power amps, even with everything else turned off, and just the power amps on, it still happens... which is where i want to fix this problem.

so short of running a new mains line and installing another outlet dedicated to the amps, does anybody have any good sugestions on how to prevent this??? or at least lessen this?

it's most anoying when you're asleep, and sudenly, because you have the sub amp under a desk where it's easy to forget about, so it's still on sudenly make a very loud pop because someone somewhere else in the house turned on a bedside lamp... done this a couple of times... not fun.

thanks for any help anyone offers.
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Old 30th June 2004, 03:48 PM   #2
sreten is offline sreten  United Kingdom
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You could fit mains filters to the amplifiers, this is a complicated
subject and there are safety issues so only do this if you know
exactly what you are doing.

I fitted a 25A mains filter to the multisocket for my system to
cure (almost, its still there but very minor) the dreaded fridge
on/off problem.

sreten.
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Old 30th June 2004, 03:52 PM   #3
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Is it a homebrew amplifier, or commercial?
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Old 30th June 2004, 04:03 PM   #4
benny is offline benny  Australia
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what about this

how about i save the work and buy one of these, or is what you're using even better?

btw, since i posted, i probed the voltage spike with my multimeter on the 1000V range (AC of course), and it jumped from 241V to 980V when i switched on/off something... probably would go even higher but that values starting to reach the end of the meters range.... i might try measuring it some other time with a simple voltage divider to see how big it is... it'd be interesting to know just how high it gets.

Thanks for your help.
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Old 30th June 2004, 04:11 PM   #5
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Benny,

sounds like you have serious spikes on your mains feed...
the mains filter you linked to seems like one way to go. You could also build something like this yourself, if you are qualified for this kind of work.
A big MOV, fused, and serious LC mains filter will probably get rid of the problem.
A small UPS could be an alternative, too. Maybe you can even find a used, old UPS for cheap (e.g. because the batteries are shot). Quality UPSs include a big mains filter.

regards
k
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Old 30th June 2004, 05:25 PM   #6
benny is offline benny  Australia
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i think they are pretty serious, because they're not just pops, they're BIG pops... i could be listening to music, and then all of a sudden BANG, there's a huge bang 5 times as loud as the music.

the pop is so loud it can wake up other people in the house... and my room is upstairs and everyone else is down stairs, on the other side of the house too! i don't have the only sound system in the house, but i do have the loudest which is why it's such a problem. 200W of subwoofer coming at you is the last thing you want when asleep. i know i should turn it off, and most of the time i do, and i also think 200W is a bit excess for my uses, but it's a relatively small SS amp that i got chucked under my desk, so it's easy to forget to turn this one off! but anyway, it;s not only when i'm sleeping it's a problem.... just whenever i got it on, even when i'm wide awake!

the big spikes i measured are of when a lamp i plugged into the outlet next to the one i measured at is turned on and off, and this always seems to produce the biggest spike, as the closer the apliance, the louder the pop. i measured it with a voltage divider so normally i was getting 100V, and the spikes range from 196 to 587V... this gives a factor of 1.96 to 5.87, meaning spikes up to 5.87*240 = 1408.8V... not nice. of course i got higher readings than that, but i am just counting those as the speed of the meter... that's just the range of the values i thought seemed reasonable because they constantly came up every time (i did it a lot of times).

the best thing about this problem is when someone turns on a flourescent that takes a few flickers to start!!! it's not as loud, but it goes, pop, pop, pop, pop pop pop, pop , pop pop pop... fun as!

thanks to those that helped...

am i qualified to do this work??? hell no... i don't got no qualifications, but i do work with tube amps with DC voltages almost twice what you get on the mains AC, so i guess i have a little bit of an idea about being safe around high voltages if this helps...

what kind of inductance and capacitance am i going to need in the LC filter?

Would a clamping voltage of 710VAC be good for the MOV? anything lower from what's available to me, and the operating voltages drop below 240VAV.

Does the max energy of the MOV effect the effectiveness of it??? is there much difference in how well two almost identical MOV's would work, only difference is one's max energy if 60J and the others is 190J?

thanks again for your help
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Old 30th June 2004, 05:57 PM   #7
sreten is offline sreten  United Kingdom
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You need a proper encapsulted mains filter, do not make it.

I've just checked mine, its actually 2.5A/250V not 25A.

It was salvaged out of a massive ancient electric typewriter.

Checking it again I also added a line transient voltage suppressor.

These simple devices (~$1) can be simply wired between live
and neutral inside the mains plug, this is how you should start.

sreten.
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Old 30th June 2004, 06:07 PM   #8
benny is offline benny  Australia
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if it comes in an encapsulated unit, why is it such a complicated subject as you say in your first post??? wouldn't it just be a matter of wiring in-line with the mains suply and devices to be protected, then insulating it apropriately, and voila? or is there something i'm missing?

thanks
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Old 30th June 2004, 06:17 PM   #9
sreten is offline sreten  United Kingdom
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http://www.ce-mag.com/archive/2000/j...armstrong.html

I'd try adding the transient suppressors first,
this in an example of a part for 250VAC in the UK :

http://maplin.co.uk/products/module....6&moduleno=499

sreten.
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Old 30th June 2004, 10:24 PM   #10
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hi again

it is a bit complicated, because this is a multi-order LC filter, with a complex load and a complex source impedance..
Also, there are regulations imposed by the energy suppliers (which obviously vary) because big caps on the line can be dangerous (unplug when charged => zap yourself), and filters are reactive.
That's a good reason to buy a ready-made filter in a box. Installation is simple, it has to be connected to L, N and PE on both sides.. in a safe box.
To arrest those spikes, use a MOV, a bit higher in voltage rating than the peak mains voltage. 700 V is too high, this will still give you pops. try sth like 350V. Use a FUSE!! in front of the MOV, a MOV will SHORT after so-many trips! Get a big MOV, it has to absorb all the spike energy. The bigger it is, the longer it will last (this is your question about max energy).
Put the MOV in front of the filter, too.

HTH
k
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