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Converter Crazy - Part 2
Last week we took a look at some digital audio basics, talking
about additional A/D-D/A converters and how they might fit
into your workflow (if you missed last week’s column
you can find it here.
This week at the Corner we will conclude our discussion of
add-on converters for Pro Tools, taking a look at some specific
examples Pro Tools LE users can leverage to extend the functionality
of their current system. I’ll also share my recent
experience with the Lynx
LT-HD and their Aurora series of
converters, a new interface option for Pro Tools HD users.
What To Look For
If you’re a Pro Tools user looking to add an additional
converter to your setup there are a few things you want to
consider before making your purchase.
Format: Since any additional converter will connect via
the digital inputs on your existing Pro Tools interface,
remember to verify the type of digital connection your specific
interface supports (see my handy table from last weeks column.
The following are common forms of digital connections found
in popular A/D converters:
S/PDIF: Sony/Philips digital interface. S/PDIF uses unbalanced
75 ohm coaxial cable up to 10 meters with RCA connectors
or optical fiber terminated with a Toslink (Toshiba link)
connector. The S/PDIF interface is found on most Pro Tools
hardware and generally supports 2 channels per connection.
AES/EBU: Audio Engineering Society/European Broadcasting
Union. AES/EBU is considered the professional version of
S/PDIF and uses a higher signal voltage. AES3 uses 110 ohm
shielded twisted pair (STP) cable with XLR connectors up
to a distance of 100 meters. AES3id uses 75 ohm coaxial cable
and BNC connectors for up to 1,000 meters. AES/EBU support
is only found on the Pro Tools HD line of interfaces.
ADAT: Used as an abbreviation for the ADAT Lightpipe protocol.
Once strictly tied to the ADAT tape machine, this protocol
is now widely used by A/D converters for its ability to carry
8 channels of audio over a single fiber optic cable. Supported
by the 002, 002Rack and HD line of interfaces.
A note about cables: When you are connecting digital devices
make sure you are using cables that support digital connections.
Just because you see an XLR or RCA plug doesn’t mean
you should rely on any old cable lying around that happens
to fit in the socket. Remember all cables are not created
equally and it is always smart to invest in high quality
cabling for both your analog and digital connections.
Number of channels: The number of channels supported varies
widely from model to model but you will commonly find units
as stereo, banks of 8, or banks of 16 channels. Some offer
only one-way conversion, while others offer both A/D and
D/A in the same unit.
Clock: Many people purchase a premium A/D or D/A converter
for its internal clock. Check out a pervious Pro Tools corner
article [http://www.audiomidi.com/classroom/protools_corner/ptcorner_39.cfm]
discussing digital clocks for more detail on this topic.
Investing in a converter that supports wordclock may provide
a more accurate synchronization in systems that support it
(Pro Tools HD, and MBOX 2 Pro).
Dynamic Range: Typically the higher this number, the better.
Good converters should have 110+ dB’s of dynamic range.
Mic Pres: While not specifically related to the A/D process,
many converters offer built in Mic Preamps. These can be
a great buy if you actually need the mic pre’s, but
if you are going to use your own external mic preamps or
mixer, this feature is not necessary and can even be counterproductive
(since you would have to deal with 2 separate gain stages).
Other factors: You may see specs listed like THD+N (total
harmonic distortion + noise) or channel crosstalk, among
others. Most people will find these to be a bit intimidating
and difficult to interpret from one converter to another,
so be sure to read reviews and snoop around the message boards
to get a sense of how people feel about a specific model
or brand and how well it interfaces with Pro Tools.
Options For LE Users
The Digi 002 Live Recording Rig
If you have a 002 or 002 Rack you may have noticed some
funny looking connections on the back of your unit and wondered, "what
are those?" The 002 and 002 Rack both support up to
18 simultaneous inputs and outputs, but only 8 of those are
analog (the other 10 are digital I/O). By adding an additional
8 channel A/D converter connected via lightpipe you can set
yourself up for some serious live recording, up to 16 simultaneous
inputs into Pro Tools.
It seems like almost every interface company these days
is jumping on this "8 more-ins" bandwagon and there
are tons of options available to suit nearly every budget.
For example, the M-Audio
Octane sports 8 channels of A/D with 8 mic preamps
built in and connects directly to your 002 via ADAT lightpipe.
Add a few
mics and you are ready to capture the perfect live drum groove
with plenty of inputs to spare for guitar, keys and vocals.
Their are many other 8 channel lightpipe interfaces with
built in mic pres that work great with the 002 including
the Behringer
ADA 8000,
Presonus Digimax
LT,
and the Mackie
Onyx 800R.
To connect the additional converter, simply patch a TOSlink
cable from the optical output of the converter into the optical
input of your 002 (the cables are one way so if you wanted
to use both inputs and outputs you would need a total of
two cables for 8 channels of i/o). Make sure both units are
powered up and choose Setup>Hardware Setup. Set the clock
master to ADAT and configure your additional digital pathways
in I/O Setup (Setups>I/O) to reflect the new connections.
The M-Box 2 Audiophile Rig
The original Mbox and the Mbox 2 (both standard and pro,
but not the mini) all support digital I/O through the S/PDIF
protocol (via RCA connectors). If you are an absolute stickler
for quality and want to set yourself up a mobile rig with
top-shelf A/D, look for a stereo A/D converter that supports
the SPDIF protocol (most do). Many hi-end preamp manufacturers
are also including A/D options in some of their models so
you can kill two birds with one stone (Check out the Apogee
Trak 2 or the
Grace
Design's Lunatec V3.
Remember only the Mbox 2 Pro supports sampling rates of
up to 96Khz. Just because an additional converter may support
higher sampling rates doesn't necessarily mean your Mbox
can except that connection. While you can still use most
converters at 44.1 or 48khz, know that you won't be able
to take advantage of higher sampling rate options on the
original Mbox and Mbox 2.
Options for HD users: Lynx Aurora + LT-HD
For those of you that don't know, Pro Tools HD systems are
much more modular then Digidesign’s LE line of interfaces.
When you buy an HD rig everything is a la carte, with a basic
system requiring at least a HD-Core card (PCI or PCI-e card
that fits inside your computer) and one qualified interface
(96io, 192io, etc). The beauty behind such a modular setup
is that when you need more DSP power or more I/O, you just
add another card or interface. While all of the HD interfaces
support multiple forms of digital connections and can interface
with almost any converter or digital box out there, many
manufacturers have begun offering options that allow their
converters to interface directly with the HD Cards, connecting
via digilink cables with no Digidesign interface required.
This functionality is generally gained by adding an additional "board" or "card" to
the interface, which allows these units to trick Pro Tools
into thinking a 192io is connected.
I recently had a chance to check out Lynx's new LT-HD card
together with their top of the line Aurora
8 converter and I thought
I would share my experience here at the Pro Tools Corner.
I must admit, as a big fan of Digidesign's 192io, I was always
a bit skeptical of any interface that "spoofed" Pro
Tools into thinking it was something that it wasn't, and
I have heard some horror stories from friends who had faced
serious down time do to these faux-192’s being incompatible
with Pro Tools software updates. After expressing these concerns,
I was assured by the guys at Lynx that this was not an issue
with the LT-HD, and being the good sport that I am agreed
to try it out and tell them what I thought.
Since the unit I was testing already had the LT-HD card
pre-installed, connecting the Aurora was super easy. I just
unplugged my digilink cable from my 192 and plugged it into
the LT-HD card on the back of the Aurora 8. After that, I
just swapped out the digi-snake cable connecting my monitors
and crossed my fingers. Amazingly Pro Tools booted up with
out a hitch, and after launching a session I was amazed at
how little trouble I had getting everything working. My first
impressions of the unit were that it sounded great. Clean
imaging and plenty of detail, everything I would expect from
a hi-quality converter. I am told that the secret to the
LT-HD’s success is that it exactly imitates the latency
performance of the 192io, so delay compensation stays accurate
without any offset calculations and using it in conjunction
with another 192 or 96io should be no problem.
Honestly I have to say that I was surprised, the Aurora
worked great and sounded great, exceeding my expectations.
Now I am not here to start any "this converter sounds
better than that converter" battles, the 192io and the
Aurora are both phenomenal sounding converters with strong
feature sets. Since I am always skeptical over any conversation
that delves into such a subjective topic, I will let the
manufacturers battle that one out on their respective websites.
But objectively speaking, the Aurora does give users sampling
rates of up to 192Khz for half the cost of the 192io and
the unit can be used as a stand alone converter via AES connections,
therefore Pro Tools HD users on a budget looking for 192IO
specs may want to check out the Aurora line with the LT-HD
option. On the other hand, if you need things like user adjustable
I/O trims, Soft Clip, and other advanced hardware setup features
found only in the 192io (or aren’t ready to call two
different support lines when you have a problem), you may
want to pony up the big bucks for the Digi branded interface.
Coming Up Next Week - Pro Tools 7.3
Pro Tools 7.3 is out! Next week we will take a first look
at the new features coming your way in 7.3 so stay tuned.
Pro Tools Tidbits
- Digidesign released Pro Tools 7.3 software for
HD, LE, and M-powered.
- Celemony’s Melodyne is now available as a RTAS plug-in
(a free update for registered users of Melodyne Studio 3,
upgrade/crossgrade pricing available for other versions)
- IK Multimedia’s Ampeg SVX is now Intel Mac compatible
(v1.1)
If you have a Pro Tools related question that you would
like me to take a shot at answering or have any feedback,
please send it to brian@audioMIDI.com.
I will do my best to select the questions that seem to stump
the most people.
As always, stay tuned to the audioMIDI.com eNews for the latest reviews and new product info.
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