Home Studio Issues / Interference

[DogHammer]

So I have myself a Focusrite Scarlett Interface, and now a set of PreSonus Eris 5 powered monitors all connected to my PC at home, to try to get into the world of recording.

When I turn the speakers on, not connected to the Audio Interface I get a bit of a hum. Nothing too loud just a little kind of buzzing hum from both speakers. But when I have them plugged into the Interface I get some crazy distorted interference sounds.

I have had a read up about interference and things I can do to alleviate it. First thing is to use shorter Phono cables to connect from the Interface to the speakers. The ones I am using at the moment are very long, like 8 meters long.... So I have ordered some short decent ones from StudioSpares.

What else do I need to think about to alleviate any interference?

[Dad3353]

I'm not expert in these monitors, but it sounds to me as if the speakers have a problem. With no input connected, and turned on, they should be absolutely silent. Ho hum, no hiss, no crackling. Just silence. Are they new..? If so, take 'em back and have them checked out. If not, take 'em to a reputable tech for a check-up. Get them silent first, then see if the distortion is an issue (it shouldn't be...). I don't think cable length alone is the cause of what you describe.
Hope this helps; tell us how things develop, please..?

[DogHammer]

Thanks Dad3353,

They are new, but both came in separate boxes, so I presume they cant both be DOA? I think I will try turning them on in another room from another power socket when I get home, see if I still get the hum.

[flyfisher]

"Crazy distorted interference sounds" seems a bit more serious than any might-be-expected mains hum, so Dad could be right about there being an actual fault somewhere. Can you test the speakers in some other way? maybe using an iPod or similar and a short input cable. Then perhaps direct into PC. Basically try to isolate the problem to a specific part of the chain if possible.

It might help if you can power everything from a single mains socket . . . Assuming there is a mains/hum/earth loop problem.

[DogHammer]

Im powering everything from the same double socket on the wall.

Monitors, Computer, LCD Monitor...

Ill do some testing later.

[DogHammer]

Alrighty.

Just got home and tested a few things. Got rid of the old Multiplug that I was plugging the speakers into for a start. Switched it with a brand new one, and that eliminated most of the idle hum.

Then realised I never actually tested the speakers with no phono cable in the back at all, and now they are totally silent minus these cables.

I have some nice short cables coming tomorrow so I shall hook them up and see if I get no interference when plugged in.

[brensabre79]

All good then.
If the phono leads pick up interference you want to might try balanced cables (if the speakers / interface will allow).

[Dad3353]

[quote name='brensabre79' timestamp='1416936632' post='2615258']
All good then.
If the phono leads pick up interference you want to might try balanced cables (if the speakers / interface will allow).
[/quote]

Yes indeed; the Scarlett has TRS balanced jack o/p, and the monitors a TRS jack i/p..! Couldn't be better, I'd say. Ignore the Phono plugs; use TRS jacks with balanced cables, and enjoy..!

[brensabre79]

[quote name='Dad3353' timestamp='1416941398' post='2615338']
Yes indeed; the Scarlett has TRS balanced jack o/p, and the monitors a TRS jack i/p..! Couldn't be better, I'd say. Ignore the Phono plugs; use TRS jacks with balanced cables, and enjoy..!
[/quote]
Nice, that's the way I'd go then.
[i]Also, with a balanced line, if you do still get some hum/interference, you can disconnect the screen at ONE end of the cable to eliminate the earth loop whilst keeping the cable run screened and getting all of the signal through.
(We used to do this to outboard gear when I installed studios many years ago.)[/i]