AD/DA converter connectivity...

L

layneness

New member
So.

I am not a super, super newbie. But there is are a few things that hours upon hours of research has not been able to teach me.

AD/DA conversion. I understand it in the most basic sense, but for a lot of the more famous converters (Protools, Apogee) I have no idea how one translates microphone'd noises into computer information though these devices.

For example, I have my microphones. I have my computer. maybe I have a plain old analog mixer. How do I use something like an Apogee AD16x or Rosetta unit or a Pro Tools HD Interface (96, 192 I/O or whatever) to translate onto my computer? Because anything that doesn't have an XLR or TRS/TS connection confuses me royally (like the multipin connector the two aforementioned units use). I understand the use of the PCI card and what it does, I'm more concerned/confused with the microphone/mixer/etc side of it all.

Pictures/diagrams would be great. I have been researching this for months and can't find a laymans explanation of how all this stuff fits together.
 
(Protools famous converters?) :eek:

Anyway - It's just the converter ("just" is a bad word, as it's a rather important piece in the chain). It converts analog to digital (to go into your computer) or digital to analog (to go to an amplifier, for example).

Microphone -> preamp -> A-D converter -> computer interface (may be part of the converter, may not be), bam - digital signal.

Digital signal in DAW -> D-A converter -> Analog signal chain or amplifier or what not.
 
haha, well, I guess maybe "name brand" converter systems would be a better term :P

so, let's say I have a mixer. How would my mixer connect to one of these devices. I know you can buy a breakaway cable from Apogee, where one end is the multi-pin plug in that fits into most of the apogee units, and then the other splits into 8 XLR plugs (male or female depending if you have the AD or DA converter, or I think in the case of the Rosetta, both) and I'm sure I've seen ones that are TRS/TS as well. is my option to plug mics into mixer (by way of preamp, of course) then have the outputs of the mixer plug into the breakaway cable, which is then converted by one of these magical boxes?
 
Massive Master said:
(Protools famous converters?) :eek:
Click to expand...

:D I think he might have been referring to the Digidesign 888's.

layneness,
There's a couple of ways the Apogee units interface with your computer. Units like the Rosetta are just straight AD/DA converters. Referencing John's example, they're the "A-D Converter" that sits between the mic preamp (mixer signal) and the interface. With a Rosetta, you're just taking the analog signal and turning it into 1's and 0's. You would still need an interface to get these 1's and 0's in and out of the computer. That's where something like the Symphony units come in... The Symphony is the actual interface that transmits the 1's and 0's to the computer.

Not all home studio's use separate converters and interfaces, though. Some do, but most folks look for the AD converter and computer interface in one box. That's what units like the Digidesign 888 and Apogee Ensemble do. They're AD converters and interfaces. You plug an analog (XLR or 1/4" cable from your mixer) directly into the box, and it converts the signal to digital and sends said signal to your computer.

If you're mixing on a desk (vs. in your computer software), you'd use the same process in reverse. The Ensemble, for example, has 8 analog 1/4" outputs. You could send 8 tracks out to these outputs, run 1/4" cables to your mixer, and mix there.
 
mkay, that makes sense. I'm familiar with the more straightforward, converter-and-interface stuff. I've done work with a Presonus Firestudio before, which was easy because it's got the 8 XLR inputs so I really didn't have to think much about it. As soon as I started researching apogee stuff and the protools HD rigs I started getting royally confused by the way it was all connected, since everything I learned on was with an old-fashioned analog board (in an old TV studio, none-the-less) so I am really trying hard to get caught up with all the digital stuff.

I am also really visually oriented. If I saw a diagram or something with a band in the studio, with a map of all the connectivity and signals, I would totally be on the ball.
 
OK Layneness! It's still just I/O's. Aside from bit depth and sampling rate, it's all about how many I/O's you have, and what the digital format for transfer is. Pretty much, digital audio output is by USB, firewire, S/PDIF, ADAT, or the increasingly rare AES/EBU. It used to be USB could only transfer 2 channels at a time, but upgrades to the USB format are changing that. Firewire can transfer a much larger number of channels, and I have no idea what the theoretical limit is. My current machine, a Digi002, can transfer 18, but the limit isn't the firewire, it's the Digi002. S/PDIF, either coaxial or optical, can only transfer 2 at a time. ADAT can transfer 8. I haven't seen an ADAT unit that can transfer more, but it may be possible. The geeks can answer that question. Whenever digital transfer takes place, one unit is the master, and the other is the slave, synch'd to the master's word clock.
In order to deal with digital audio transfer, all you really have to do is figure out how many simultaneous inputs you need that have to be processed separately. Increasingly, if you want more than 2, you use a firewire based unit. Then you need a computer with sufficient memory, enough processing, enough RAM, and a firewire card. If you only need 2, USB or firewire both work. ADAT and S/PDIF are more often used for transfer between audio devices than direct to a computer, although you can go into a properly enabled computer by S/PDIF. Thr coaxial version of S/PDIF uses an RCA to RCA cable, and the optical version uses a fiberoptic cable. Optical ADAT, also known as "lightpipe", also uses a fiberoptic cable, the same as is used for optical S/PDIF, but can transfer more signals.

So basically, an A-D convertor is just a magic box that takes a regular old line in and what comes out is USB, or firewire, or whatever. Digital transfer of data, especially optical transfer, has numerous advantages. First, it can allow you to bypass the cruddy A-D conversion of cheap gear, by sending it a signal that is already digital, which can also bypass the cheap preamps in a lot of recorders. For this reason, as an example, I plug my mic into a Joemeek twinQ, a 2 channel preamp, and then into a Roland VS1824CD, a digital recorder. I could send it a line out, but then the Roland would mess up my perfectly good signal with it's cruddy preamps, and its cruddy A-D conversion. The twinQ, while not a great A-D convertor, is better than the Roland, and as a preamp, it is waaay better. So I send the signal to the Roland by the twinQ's optical S/PDIF output, using the Roland really as a mixer, which it is pretty good at, and as a computer hard drive to store the digital data. The Roland's pres are simply not involved.

The other advantage of the optical transfer is- it is immune to interference, because it is not electromagnetic. I can run that optical cable right over power cords and transformers without a hiccup. It's really not that tough. It's just that everybody talks in anagram technobabble until your eyes glaze over, Best of luck.-Richie
 
Just some visual representations of how everything fits together...

Interface, with everything integrated together. The 'interfacing stuff' is just the various chipsets and stuff required to interface the converters with the computer.
slide1.png



With standalone converters, everything is seperated. The preamps can be standalone preamps, or pre's in an analog mixer. In other situations you might have a digital mixer with pre's and converters built in, which then outputs over ADAT.
slide2c.png



Protools HD works in a very similar way, but with the Protools converters and their proprietory link to the Protools HD cards in the computer.
slide4.png



Digidesign also produce an 'adat bridge' allowing you to use other converters (Apogee, etc) that have ADAT outputs.
slide3.png
 
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