Originally Posted by DarthAcer
To ability to take care of grounding. Between laptop, PCCard, and audio device you are not as much in control of what's going on in each component. It's a lot easier with desktop computer. Laptop's are generally terrible to deal with.
But, the grounding issue is very minor since signal travels in digitized form over Firewire. I forgot about that
Um the signal being digitized has nothing to do with ground loops being or not being formed. A ground loop can be formed by a laptop and a firewire connection just as easily as it can with any other interface. It depends on how the grounds are handled.
And yes ground loop issues are quite easy to handle once you understand them in audio. Interference being picked up by poor signal rejection is completely seperate and I believe that is what you were referring to. That is the majority of the reason that most people do not use onboard sound cards for any professional work. There is poor signal rejection. Well that and the lack of features
Lemme see if I can give a basic rundown on grounding, and ground loops in audio involving computers...
Actually nevermind, Wikipedia seems to have a pretty good run down on it and even ways to address it in audio.http://en.wikipedia.org/wiki/Ground_...electricity%29
Originally Posted by Wikipedia
In an electrical system, ground loop refers to a current, generally unwanted, in a conductor connecting two points that are supposed to be at the same potential, that is, ground, but are actually at different potentials. Ground loops can be detrimental to the intended operation of the electrical system.
What this translates into for audio is in general a ground loop will occur when there is a different electrical potential to ground between two pieces of equipment that are connected via audio cables. Since electricity allows takes the path of least resistance, the one with a higher resistance path of travel to ground ends up transfering electricity via the audio cable ground to through the other piece of equipment to ground. This in general shows up as 60Hz hum in the US, but when dealing with computers shows up in computer audio in other ways as well, including a clicking/buzzing sound that increases,decreases with HD speed, mouse movement, etc. In the case of a ground loop it is usually not affected by volume adjustments, as the noise is not coming from the audio, but rather from the ground, that is used as a signal reference to the audio signal.
This is why isolating the ground, on a 1:1 transformer will prevent a gorund loop, it isolates it so that both pieces of equipment will use their respective paths to ground for their AC power, and not use the other piece of equipment as a path of lesser resistance.
It is also why having all the equipment in a small system plugged into the same outlet works well as it ensures that each piece of equipment has the same potential to ground.
Two seperate outlets in the same house do not nessecarily have the same potential to ground. If one runs directly to ground, but one has a dirty connection or two inbetween, the one with the dirty connections will have a higher resistance. If two pieces of equipment are connected to both of these outlets and connected via audio cable, you will likely here the ground loop happening.
|I do not know of any low end Firewire audio
You obviously haven't looked hard enough. Take a look at sweetwater, and pretty much any of their budget stuff they offer. I would imagine consumer manufacturers also make a few fire wire interfaces as well though I haven't looked in so long I can't say for certain.