Started getting this horrible buzzz

Spirit · Post by **Spirit** » Mon Sep 29, 2003 3:35 am

My little studio / office is packed with gear. There's two main computers, laptop, scanner, printer, five screens, fax, keyboard, video, DVD, DAT etc etc - but until recently everything's been quiet.

But just in the past few weeks I'm getting a terrible humm through my speakers (NS10s). I suppose it's a ground lopp of some kind ??

All I've done recently is move the positoon of one monitor (to a less cluttered spot), and added another LCD screen.

I've no experience in tracking these things down or even what exactly causes them.

Any clues greatly appreciated.

emzee · Post by **emzee** » Mon Sep 29, 2003 4:01 am

My understanding...usually caused through connected pieces of gear which have been connected to different power points. This gives several connected earth points instead of one common point, and can result in a small current flow between the equipment earths...instead of direct to earth.

Usually fixed by ensuring connected audio gear is plugged into one common point. ie anything in your audio signal chain goes to one power point.

Check any connected earth wires on amplifiers etc are still connected.

Check your screens are not suddenly close to speakers. Unless they are shielded, speakers can be affect by EMF from a cathode ray monitor.

Also check that your low level signal cables are not beside 240v mains cable. This could induce hum into your signal.. (less likely than above)

That's about all I can help with..maybe others can assist further.

Let us know what solves the problem.

[ This Message was edited by: Mikka on 2003-09-29 05:03 ]

Counterparts · Post by **Counterparts** » Mon Sep 29, 2003 4:13 am

Have you tried turning off the (computer) monitors...does that make the buzz disappear?

Monitors are very noisy beasts...I have to turn mine off when recording (esp. guitar) due to the amount of noise it creates.

Royston

emzee · Post by **emzee** » Mon Sep 29, 2003 5:46 pm

[POST EDITED: CONSIDERED UNSAFE PRACTICE]

....Also check leads...maybe one has fractured and is no longer earthing...probably should have been my first suggestion but I seem to think backwards..

[ This Message was edited by: Mikka on 2003-09-30 04:17 ]

bassdude · Post by **bassdude** » Mon Sep 29, 2003 6:46 pm

IMPORTANT! Do not remove earth connections from power leads. This is the absolute wrong way to correct ground loops and is EXTREMELY DANGEROUS!

If you must break the earth then do it at one end of the interconnecting signal cables IE break the "signal" ground not the earth in the power cord.

Here is a very good, easy to understand (with pictures) doco that explains the CORRECT way to solve ground loops:-

http://www.rane.com/note110.html

(PS Sorry Mikka, not trying to jump down your throat or anything but breaking the earth connection is actually illegal in Australia not to mention dangerous!

)

Anyway, getting on to Spirit's problem. If it is actually a buzz and not just a hum then it may not be a ground loop but a bad signal ground/earth somewhere eg a cable's ground connection gone bad.
Either way, best way to track it is from the monitors back to the source.

Disconnect everything. Then, starting from the monitor amp driving the ns10's, reconnect the individual devices in the signal chain until you connect something that starts the buzz. Be careful to turn the monitor level all the way down as you re-connect the individual devices.
Once you plug in the device that starts the buzz it may indicate that either the device/cable is faulty or you need to re-think how to connect it.

[ This Message was edited by: bassdude on 2003-09-29 20:00 ]

emzee · Post by **emzee** » Tue Sep 30, 2003 2:18 am

I don't take things like that personally...so thanks for jumping in.....That point came from a USA amp book on running two guitar amps at once....I didn't realise it was illegal here, so thanks.

[ This Message was edited by: Mikka on 2003-09-30 03:20 ]

krizrox · Post by **krizrox** » Tue Sep 30, 2003 8:19 am

If you do a search here on PZ, you'll probably find a ton of info on the subject (a lot of it from me personally).

Undo the things you did right before the problem started and see if that helps. If not, then the best way to attack the problem is to break everything down to the lowest common denominator and then start adding things back until the problem reappears. It can be a time-consuming and frustrating experience, believe me, to track down ground loops and noise. But the effort will usually produce positive results. I spent a good month experimenting and trying different solutions before I finally resolved my problems. Good luck!

Not that this helps, but it seems to me the weakest link in the audio chain is the AC source. We're dealing with technology that is how many years old now? While other technologies have improved and evolved, AC is the same old noisy mess it's always been. Our cable TV service has been modified and upgraded many times in the past 20 years. And not everyone has cable TV. You'd think they would have figured out a better distribution system for AC by now. We had a major power outage here in the USA recently. Our power grids are antiquated and starting to fall apart. We'll probably never see a major rebuild in our lifetime (we're too busy spending our money rebuilding Iraq) but it would be nice if it did happen soon.

Spirit · Post by **Spirit** » Tue Sep 30, 2003 9:12 am

Thanks for all these suggestions, much appreciated. I'll knock it all back one by one and see who's guilty

bassdude · Post by **bassdude** » Tue Sep 30, 2003 7:52 pm

On 2003-09-30 03:18, Mikka wrote:
I don't take things like that personally...so thanks for jumping in.....That point came from a USA amp book on running two guitar amps at once....I didn't realise it was illegal here, so thanks.

No worries Mikka. You would be surprised how much this is still practised out there. What I don't understand is how much the safer solution, ie breaking signal ground, gets overlooked!

Spirit · Post by **Spirit** » Wed Oct 15, 2003 10:01 am

No joy yet. And the hummmmmm just seems to be getting louder although I think it's just a measure of my irritation, not reality.

Excellent link BassDude, thanks.

Spirit · Post by **Spirit** » Thu Oct 16, 2003 12:18 pm

Arrrghhh !

I'm getting nowhere with this hum and it's driving me crazy. It's a pitch that you can actually hum -

Do I need to physically unplug each device - power and audio leads ? Or just power ? And should the humm then disappear immediately if it's to blame ?

Post by **garyb** » Thu Oct 16, 2003 12:22 pm

1.yes,disconnect each piece completely.
2.yes,the noise should stop immediately when the problem is found.

the computer ps is a prime suspect but any combination of items could be where the problem is...a broken sheild on a cable is also always a possibility...

[ This Message was edited by: garyb on 2003-10-16 13:23 ]

bassdude · Post by **bassdude** » Thu Oct 16, 2003 7:56 pm

Take it a step at a time. Disconnect everything. First connect the monitor amp up to your monitor speakers and turn on. Any hum? No? Turn off the amp( or turn volume down). Connect the next part of the signal chain, output of mixer or computer whatever and turn the amp back on. Any hum? Just keep going adding everything back into the signal chain until you find the culprit.

You don't have to disconnect the power, just make sure all signal interconnects are disconnected.

Spirit · Post by **Spirit** » Thu Oct 16, 2003 11:57 pm

OK ! Now I'm gettinmg somewhere.

I unplugged everything - and the amp was still humming like mad. Oh no I thought, the amp is stuffed...

So I start to plug everything back in. Then, with one particular connection there was a crackle and the hum stopped !

So, just a bad input on the amp ?

I feel like the studio has suddenly been moved into a peaceful green glade.

Thanks for all the advice.

bassdude · Post by **bassdude** » Fri Oct 17, 2003 2:09 am

Good news! But that amp needs to get checked out. There should be no hum even with no input connections. Could be bad signal grounding. Also if it turns out the chassis earth is bad then that puts you at risk safety wise.
Shame your not in Can'tberra, I could take a look for you.

Spirit · Post by **Spirit** » Fri Oct 17, 2003 3:07 am

Didn't realise that.... I will take it to a place I know. Thanks again Bassdude

Post by **garyb** » Fri Oct 17, 2003 12:24 pm

bad ground..probably the connector.

Spirit · Post by **Spirit** » Sat Oct 25, 2003 2:55 am

garyb: bad ground ?

When I fiddled with the RCA cable and input on the amp there was a crackle and the humm stopped.

But after a short while the humm comes back !

But what I find is that if I take the cable out, then put it back in again, then again there's a little crackle and the hum stops.

But it doesn't matter if I change the cables to the amp, nor does it matter which RCA inputs I choose - I get the same effect on all of them.

So do I need to unplug this amp and get it fixed, or is it a deeper problem and I should just chuck the amp ? It's getting a bit old anyway......

Thanks everyone for your persistant help with all this

[ This Message was edited by: Spirit on 2003-10-25 03:55 ]

bassdude · Post by **bassdude** » Sat Oct 25, 2003 7:18 am

It really sounds like it may be a dry joint on the PCB inside the amp or a bad connection inside. Have you got another amp that you can try out for a test?
If it's a good quality amp then it might pay to get it fixed. It doesn't sound like an expensive fix to me (especially if it is just a dry joint/bad connection).
If the amps very old then it could be related to failing filter caps/dc blocking caps.

Post by **garyb** » Sat Oct 25, 2003 1:06 pm

you can probably fix this yourself if you know how to solder.otherwise,it's a $60(u.s.) or so problem.(as a guess)