Hiss from monitor speakers - driving me crazy!

My monitors are hissing like crazy, can someone help me isolate/fix the problem?

- KRK RP6 monitors plugged into a extension cable

- Hiss is the same at all volume levels

- When the speakers are not connected to the Apogee Duet interface, they are perfectly silent

- I recently took the whole setup elsewhere for the weekend and there was no hiss at all, despite everything being exactly the same setup as at home.

I'm thinking the only thing it could be is power related. There's a 4 way splitter which powers the mac, screen and the 2 monitors. It goes straight into a wall socket. Could that possibly cause the hiss and if so how would I rectify the problem?

I'd focus on this. I haven't used the Duet, but if it only happens when it's connected, that should tell you something.

But when I took it to another house everything was fine. I think it's power related...I guess the question is more what can be done to prevent hum/hiss from a power related source?

Oh I missed that part.

I've never heard of hiss coming from power issues.

Its highly unlikely the power. The only theing the power can do is be higher or lower than the other location.

That night supply more or less power to the power supplies, but the power supplies are regulated so the DC voltage

that comes out of them and supplies the circuits will be the same no matter what.

My guess is you have a gain issue with the apogee.

Theres either a setting thats set too high or something has gone funkey on you.

not much you can do besides swap cables.

His is almost always DC related. Noisy preamp, preamp gain too high, something loose on a circuit board, bad cap

bad transistor or IC pack and the signal gets bcontaminated with white noise.

Hiss is common in cheap audio components. The silicon solid state devices used have more impurities in the manufacturing process

and this causes electron collisions when the signal passes through them. Thats what creates the typical solid state hiss. High quality components

have less impurities which makes the parts more expensive to manufacture.

With an interface you have a preamp and converters. It may be acting as a radio reciever and picking up stray noise from some place in the room.

You can usually isolate it bu moving things around, moving wires, monitor position, stuff like that. Maybe (Mabe) a noise filter can help block noise coming in on the AC liine or being transfered from one unit to another through the ac jacks. Its not impossible but it would be a sign of something going funkey. The UL standards

thet regulates electronic devices is usually enough to prevent this. If something was degrading and creating noise, it wouldnt fix itself unless there was someting intermitant.

So a loose solder joint in the Apogee might be my best guess if it comes and goes.

try a ferrite choke? It's possible that you could have something coming through in the DC that's bleeding into your audio.