As my post title suggests no matter what I do I have a slight "hum" from my speakers.
 
This is only noticeable when I have no music playing, so I suppose my question is, Is there something wrong causing "hum" or is this normal?
 
I put this down to using cheap gear in the past but I have upgraded quite a bit of my gear recently but the "hum" is still there.
 
Should a studio set up be completely silent when nothing is playing?
 

Yes a studio setup should be perfectly silent when no music is playing. Anything less is unacceptable in my opinion!
 
What is your interface. What are your monitors etc.. How are your speakers connected etc... There might be something you can do in terms of linking those two that could eliminate hum. Using balanced lines etc. Possible earth loop hum might be present etc...
 
 

Jeff Evans
Yes a studio setup should be perfectly silent when no music is playing. Anything less is unacceptable in my opinion!
 
What is your interface. What are your monitors etc.. How are your speakers connected etc... There might be something you can do in terms of linking those two that could eliminate hum. Using balanced lines etc. Possible earth loop hum might be present etc...
 
 

Thanks Jeff, That's what I thought.
My audio interface is an m-audio fasttrack. I know this is a cheap and cheerful interface but could that be the cause?
I just got a pair of JBL LRS308 monitors but I have them connected using a breakout cable (mini jack - 2 x 1/4 jacks) is that balanced? (excuse my ignorance) 
 
Should a better interface with 2 xlr outs yield better results?

Yes that interface is not very pro I guess. A decent interface with balanced outs on TRS jacks would be much better. Mini jack outs are a bit poor IMO.
 
But you could start by making two leads like this:
 

 
Except on the unbalanced end that now shows a 1/4" mono jack you need to substitute that for a mono mini jack plug instead. This lead prevents any earths from being used at the speaker end but gets the signal into the balanced part only. The shielding will still work because the shield is still grounded at the balanced end.

Jeff, you are a legend! Tell me you didn't just draw this out on my behalf?
 
Gonna try this. Thanks!!

No I had to draw it out for someone else on the Presonus forum so I had it already. I have tried to explain this but a picture is worth a thousand words as they say.
 
Something else too. If you disconnect both speakers completely and plug phones into that interface do you still hear any hum? That will eliminate the interface itself as a possible source of trouble. eg if the hum is still there then it is the interface and not connections between interface and speakers as first thought. If it is silent in that test it means there is another issue connecting to speakers.
 
There is no guarantee that lead will eliminate the problem either but it does in a lot of cases. It also stops that dreaded laptop noise from getting into mixers too. You just need balanced inputs though that is all.
 
A handy lead to make is a stereo mini jack out to two balanced TRS 1/4" plugs wiring the same way. Except in the mini jack end the two ring wires are strapped togther and soldered to the sleeve of the stero mini jack.
 
 
 
 

Jeff's drawing may help if you have a problem ground loop between the interface and the amplifier.
 
Here's the thing - ground loops are not bad, and in fact they are virtually unavoidable. The problem really stems from some very poor design/manufacturing choices made by companies that haven't read the AES standards for interconnections yet... well, or ancient Bell and BBC documents (the ancients are stealing our ideas!)

Before you make up new cables may I suggest a simple test to find the problem?
Disconnect the amplifier inputs and crank the amplifier all the way up and listen - do you hear hum, or just white noise? If you hear hum then there is a problem between the interface and the amplifier, and Jeff's cable will probably solve it.
 
If not then the problem exists elsewhere, so you want to add gear back in, one link at a time. So now connect the interface to the amplifier, but leave the rest of the interface connections disconnected. Still no hum? Now add the rest of the interface connections, one at a time. If it turns out that you get hum after adding two more connections then disconnect the first one and see if the hum goes away.
 
I recently had a problem where I only had hum when I had both left and right line inputs connected to a Presonus Firebox. Following that test procedure I discovered a bad connection is one of my cables. A couple minutes with the soldering iron solved it.

One last thought (at the risk of repeating myself) DO NOT, UNDER ANY CIRCUMSTANCES, USE ANY TRICK THAT DEFEATS THE SAFETY GROUND!!!!!! Sorry, but this is an only wives tale that still floats around the internet from time to time.... so I figured I'd be proactive<G>!

Power line noise is annoying, but it is usually quite easy to resolve, once you find the source(s). Please let us know how it turns out.

And if you are looking for some additional reading, the top documents on this topic include (among others):
Dennis Bohn's Rane Note #110 - a classic, well regarded paper that covers the topic well!
Bill Whitlock's Troubleshooting Guide, and App Notes on Interconnections and Hum and Buzz (actually, everything on their web site!)
There are many others, but these will get you started<G>!

Thanks for your help guys and sorry for the late reply.
 
I isolated the problem to my cables using the methods you suggested  - disconnected everything and truning up the volume etc. to test the speaker amps (now why didn't I think of doing that!)
 
Anyway new cables and problem solved. This hum has annoyed the bejaysus out of me for a long time.
 
As always I am most grateful 

I love a happy ending!

I was going to say, the Fast track has balanced outputs. Used to own one but got rid of it because it was not quiet. My issue was more of a screaming sound that I later read about being caused by using USB buss power. The pre amps were real sad too, but I mostly used it with the SPDIF and my digital mixer . But you just couldn't get used to that scream in the background.