Monitor hum

[Frederik654]

Hi guys,

I just switched my level pilot for an SPL monitor controller (which I already had but the Level Pilot was an easier solution but it crackled).

Connection between the SPL and Genelecs is Jack to XLR and cables run for 1 meter each.

Audio card is an Audio4Dj with cinch to cinch on the SPL. I have a lot of static and wireless noise coming from the computer into my speakers.

The monitors, computer and SPL are on grounded outlets and the important thing is, this was not the case with the level pilot and nothing changed. The level pilot is way inferior to the SPL but I got the noise and it's really bothering me ! The LP is static and the SPL is powered, maybe there ??

Can anyone give me an idea between the level pilot internals and the SPL ? Maybe not true but is it possible that the Level Pilot is so inferior to the SPL that the static noise was not audible ?

[ark]

I suppose the first step in troubleshooting is to figure out where the interference is being picked up. Apparently you have two cables between your computer and the monitors for each channel: One between the computer and the monitor controller; the other between the monitor controller and the monitors. So the obvious question, I guess, is what happens when you disconnect your computer from the SPL. Does it still pick up noise?

The other question is whether the cables that you are using to connect the SPL to the Genelecs are wired properly. In particular, are the 1/4-inch ends TRS, and is the S connection independent of the other two?

[m.nowakowski]

I'd like an answer to this one too! I have Genelec 8040 hooked to a focusrite saffire LE interface. As soon as I disconnect the interface cable (firewire) the noise is gone.

I have tried different cables but the problem is still there...

No idea really

[ark]

I'd like an answer to this one too! I have Genelec 8040 hooked to a focusrite saffire LE interface. As soon as I disconnect the interface cable (firewire) the noise is gone.

Aha! I'm guessing that the Saffire gets its chassis ground from the Firewire cable, which gets it from the computer, which is probably ungrounded because it has a decoupled power supply.

The Saffire has balanced outputs. How are the cables wired that you are using to connect the Saffire to the Genelecs?

[m.nowakowski]

I'd like an answer to this one too! I have Genelec 8040 hooked to a focusrite saffire LE interface. As soon as I disconnect the interface cable (firewire) the noise is gone.

Aha! I'm guessing that the Saffire gets its chassis ground from the Firewire cable, which gets it from the computer, which is probably ungrounded because it has a decoupled power supply.

The Saffire has balanced outputs. How are the cables wired that you are using to connect the Saffire to the Genelecs?

The cables I'm using are two (one for each monitor) standard XLR cables with an XLR to jack converter to be able to connect them to the saffire! So you think that the firewire cable is the problem here? Should I get a new more expensive one?

[ark]

So you think that the firewire cable is the problem here? Should I get a new more expensive one?

No.

I'd like to know exactly how the audio cable that connects the Saffire to the speakers is wired. In particular, is the Saffire end a TS or a TRS connector? If you don't know the difference, please look here.

If you are using a TS connector, I would start by replacing those cables with fully balanced cables with a TRS connector on one end and an XLR on the other. If that still does not work, then you may still be able to solve the problem by connecting the ground (i.e. the shield) only on one end. The easiest way to do that is probably to interpose one of these between the XLR connector and the speaker.

If that doesn't work, the next thing to try is transformer coupling, but that starts getting expensive, so let's try the simple stuff first.

[m.nowakowski]

So you think that the firewire cable is the problem here? Should I get a new more expensive one?

No.

I'd like to know exactly how the audio cable that connects the Saffire to the speakers is wired. In particular, is the Saffire end a TS or a TRS connector? If you don't know the difference, please look here.

If you are using a TS connector, I would start by replacing those cables with fully balanced cables with a TRS connector on one end and an XLR on the other. If that still does not work, then you may still be able to solve the problem by connecting the ground (i.e. the shield) only on one end. The easiest way to do that is probably to interpose one of these between the XLR connector and the speaker.

If that doesn't work, the next thing to try is transformer coupling, but that starts getting expensive, so let's try the simple stuff first.

Oh I didn't know about TS and TRS! I now noticed that the XLR to tele converters are TS (tip, ring and only one black sleeve):
http://en.wikipedia.org/wiki/File:Jackplug.jpg
This seems to be the issue! I'll get a new pair of converters (or new cables) that look like this tomorrow:
http://en.wikipedia.org/wiki/File:Photo-audiojacks.jpg


I'll make sure to report if there is a difference! Thanks a lot ark! I hope this can help out Frederik654 as well

[Frederik654]

Well i hope so

On the other hand it's still strange that with the level pilot there was no hum at all.. Will do some testing tommorow.

Tx for the help guys !

[ark]

Could it be possible that the Level Pilot isolates its input ground from its output ground?

[dancerchris]

The noise can be coming from a lot of sources. The monitors amp itself could have some noise (for various reasons, noisy power, poor circuitry etc.). Use a different source for your audio in to check that out. The firewire could be causing a ground loop. If that's the case going to a better grade cable won't help. Going to balanced won't help either. You'll need to lift the ground somewhere. But there are other possibilities also. Make sure you are using the right input levels to the monitors. Some monitors can automatically sense the input level, e.g. +4dB or -10dB. My Mackies have a switch on the back to change it. Noise problems can drive you to distraction, but usually it is something that is poorly grounded and not all this esoteric BS that Monster and other people will try to get you to buy their overpriced junk for. Same story with conditioned power.

My $0.02

[ark]

The noise can be coming from a lot of sources. The monitors amp itself could have some noise (for various reasons, noisy power, poor circuitry etc.).

Genelec? Naah, not unless they're broken. Anyway, the noise goes away when the input source is removed, so it's not the monitors.

The firewire could be causing a ground loop. If that's the case going to a better grade cable won't help.

Agreed.

Going to balanced won't help either. You'll need to lift the ground somewhere.

But you can't do that unless you've gone to balanced first.

[MartinOM28V]

Ground loop is most common problem. Lots of online help. Firewire cables can make a big difference though--ones that ship with high-quality audio devices are usually ok but generic cables tend to be noisy. Good luck

[dancerchris]

If you think it is firewire unhook it. It is a hot swap cable so you can unhook it real time. (Do that while the audio is not playing but speakers on and audio interface volume at a mid level.) If your noise goes away, bingo. However if it does, just replacing the cable may not fix the problem. The shield on the firewire could be conducting the ground loop noise. (I've also had ground loop where the noise stayed even after unhooking the firewire cable.)

[blakbeltjonez]

try AC ground lifting one of the devices connected - i would start with the SPL, try one device at a time. try also AC ground lifting everything on your strip or wherever all your power meets just to see at first, then work your way around each connected device.

it's definitely a ground loop. easily eliminated with some diligence and a 50 cent ground lift.