Interfaces... Help

[tommyboy101]

Hi there all.

I'm investigating a HD rig, at the moment I am only running LE.

I understand about the HD I/O and Pre but what interface do you use to get sound out of Pro Tools, like your outputs. Do avid make one?

This is probably a really obvious and stupid question and I apologise for this. Thanks for any help. :)

[Bill Denton]

Forgive me for picking on you a bit...

If you know that the "I" in "I/O" stands for input, what do you suppose the "O" might stand for?

The new I/O's can be configured with varying numbers of both analog and digital inputs and outputs.

We'll skip the digital I/O in this discussion for the sake of simplicity.

In the basic 8 x 8 I/O unit, you have 8 line level inputs and 8 line level outputs.

In the simplest scenario, you would connect the mono out of a keyboard into input 1, and a pair or powered monitors to outputs 1 & 2. You would then set an audio track in Pro Tools to record from input 1, and to playback through outputs 1 & 2.

And that's all there is to it.

However, if you want to record using a microphone, you would need to have a preamp. You would connect the mic to the preamp input, and the preamp output to input 1 on the I/O.

(Actually, you could connect your devices to any of the inputs or outputs on the I/O, then set Pro Tools to input from our output to the chosen inputs and outputs on the I/O).

Keeping it simple, the I/O expects its inputs to receive a relatively "loud" signal. And since a keyboard puts out a relatively "loud" signal, you can plug it directly into the I/O. But a mic puts out a relatively "soft" signal, so you use a preamp to raise the relatively "soft" signal put out by the mic to the "loud" level expected by the I/O.

Which brings us to the Avid Pre...

Basically, the Pre is simply eight preamps in one box (it has some other features, but they aren't important to this discussion). You plug a microphone into one of the preamps, and feed the output of that preamp to an input on the I/O.

The I/O does what is called A/D D/A conversion. It takes an analog signal, such as that from the keyboard, and turns it into a digital signal that can be used by your computer (and Pro Tools). It also takes the digital signals sent by Pro Tools and your computer, and sends them out to something like the powered monitors used in the original example.

So, in the HD world you have one "box", the I/O, that does the A/D D/A conversion, and a separate "box" containing one or more preamps (8 in the case of the Pre), to make the mic signal loud enough to feed the A/D D/A "box".

But in the LE world, you would typically be using something like either an MBox or a 003. The MBox and the 003 both perform the A/D D/A conversion, but they also have one or more preamps built into the same box.

So, where you need two separate "boxes" in HD, both functions are perfromed by one "box" in LE.

I hope this gives you enough info to enable to to begin reading the Avidesign documents on these various pieces of equipment, which will give you much more information than just this simple explanation...

[tommyboy101]

Thank you for that very detailed explain, however Forgive my total ignorance here but, where are the line level inputs on the HD I/O? Again apologies for my quite obvious questions. :)

[axiom]

You connect a snake to a DB25 connector on the back.

[nst7]

Also, with the HD I/O, or the old HD192, etc., you would need some kind of monitor controller, at least to have a volume knob, and also a mute or mono button, etc. So that's something you need to budget for as well. One nice thing is that the new HD Omni has these features, as well as some more inputs/outputs and a couple of preamps.

You could start with the Omni, and get the HD I/O later on. That might be a good way to go, unless you absolutely need more inputs/outputs right away.

[Bill Denton]

Expanding on what axiom said...

The inputs and outputs on the I/O are brought out to DB25 connectors on the back of the unit.

There are two basic types of snakes you would use to connect to these DB25 connectors:

A DB25 / TRS cable has the DB25 connector on one end of the snake, and individual TRS male connectors on the other end. You could then plug these TRS plugs into equipment such as the output of a keyboard, or the output of a preamp. However, once you start playing in the HD league you'll probably start using one or more patch panels. And in this case you could use a patch panel that has TRS connectors on the back, and plug the TRS connectors on the snake into them.

There are also cables that have a DB25 connector on both ends. You would use these if you were connecting the I/O to a C|24 control surface, which also uses DB25 connectors for input and output. There are also patch panels that have DB25 connectors, and you could use one of these cables to connect your C|24 to your I/O.

So why use DB25 connectors? For one reason, they typically provide better electrical and mechanical connections. Then there is the problem of trying to get all of the connectors in the limited space on the back of the equipment. You can put one DB25 connector, which can handle eight "channels" of input or output in the same amount of space that is taken up by three TRS jacks.

And BTW: A DB25 connector looks sort of like the ones where you would connect an old VGA monitor cable to the back of the computer...

[tommyboy101]

Thank you for your answers. Am I right in saying the only Avid interface that has output controls is the omni. What other brands do you suggest for this type of thing. :) thanks again. You guys are great. :)

[nst7]

Yes, the Omni is the only HD interface with monitor control. As for monitor controllers in general, they're all over the ballpark pricewise and qualitywise. Here's a link to some that Sweetwater sells:

http://www.sweetwater.com/c417--Monitor_Management

One of the best values for the money right now is the Dangerous Dbox. Ignoring the analog summing section, simply as a monitor controller it's great quality/price value.

[Bill Denton]

Originally Posted by tommyboy101

Thank you for your answers. Am I right in saying the only Avid interface that has output controls is the omni. What other brands do you suggest for this type of thing. :) thanks again. You guys are great. :)

Just to clarify, the I/O has outputs, but you would need to feed them to a monitor controller unless you are using something like a Command 8 or a C|24, which have built-in monitoring capabilities.

In addition to its input/output capabilities, the Omni has a built-in monitor section that allows you to select between 2 sets of monitor speakers, do 7:1 surround, and some other stuff I'm too lazy to look up. Again, this is very similar to what the 003 offers (except 003 doesn't do surround).

What you really need to do at this point is start determining exactly what you want to do with HD; a bedroom studio or a 100,000 square foot production center. Once you get that figured out, along with your budget, we can start giving you much better recommendations for what you need...

Good luck!