XO Wave is now discontinued
as we prepare to bring you the next generation
Digital Audio Workstation called
This site remains available for anyone who
purchased XO Wave in the past.
However, please keep in mind that as discontinued software:
- This site may not contain up-to-date information.
- Technical support is discontinued, though we will do our best to continue to provide
email support, especially to anyone who purchased recently.
XO Wave: Guide to Home CD Mastering
CD Mastering is a complex subject. However, not only is it possible
to create high quality CD masters at home, but thanks to XO Wave,
it's possible to do so on a (tiny) budget. This guide describes what everyone
needs to know about the process in order to get the best possible
results. Almost everything here applies whether or not you
are using XO Wave as your CD Mastering software.
First off, a little terminology: When you and I and most audio
professionals talk about CD mastering, we mean setting up
the audio, marking tracks, setting up CD Text, and so on, in order
to have something to send to a CD manufacturing plant. However,
the CD manufacturing plant calls this process "pre-mastering".
To them, a CD master is a disc made of glass that has been
prepared by them to a client's specifications, and is used
to physically stamp its impression onto
pieces of plastic, 'pressing' CDs. Audio folks
usually refer to this as the "glass master".
How the audio world and the CD manufacturing industry ended
with conflicting terminology, I don't know, but for this
page, I'll use the term 'master' to refer to what you send to
the CD manufacturing plant, and 'glass master' to refer to
what the manufacturer calls a master.
The CD medium does not lend itself to accurate duplication.
The original techniques for preparing the glass master didn't
involve burning a CD on your computer because blank CDs and the
technology to burn them simply did not exist until some time after CDs became available, and so care was
not taken to ensure that burned CDs could be used as masters for the
CD manufacturing process.
There are three types of problems that may arise when you use
a burned CD as a master for the manufacturing process:
chronological offset, disc errors, and manufacturing errors.
Chronological offset is essentially a mechanical
problem. CD players are not required to play back
exactly from the start of a track, and many burners shift the
audio in time by up to a few hundred samples. These
types of errors are relatively easy to deal with, as long
as you know about them and are prepared. disc errors are a
result of imperfections in, or poor quality of, blank media
or burners. Although this can be a subtle problem, the use of
high quality discs and burners will keep you safe.
happen when your finished disc is not the same as the master
you sent. To avoid this type of error, many manufacturers offer
to send you a burned CD that will be exactly the same as the
CDs they will press. This may add slightly to the cost and
time to manufacture your CDs, but there is no substitute for the
peace of mind it offers.
In general, if you have any concerns
about the process, the best place to seek advice is from
the manufacturer. There is no substitute for their knowledge and
experience and they know what will and won't happen
during the process. If you have concerns after reading this
you should bring your concerns up with them, and ask how they can ensure
that your CDs will be manufactured exactly as you want them.
CD technology dates back to the 70's. The hardware used to spin the
disc, read data, and accurately buffer the audio and other data
on the CD was simply not as sophisticated as what is
available today. As a result, the audio CD standard (called
"red book" after the color of the book containing the official specification)
specifically allows players to do things like start playing
a track after the actual location of the track marker. CD
burners carry on this tradition, and they also allow a certain
amount of inaccuracy when putting the data onto the disc. This
offset is usually small (around 100 samples). This offset is usually
not important for the way your CD sounds or is played in
any noticeable way, and generally pales in comparison
to the offset created by CD players when playing back your
It's important to understand that neither of these issues affects the actual
sound quality of our CD, just how it is played back. For example,
if track 2 of your CD starts right on the first drum hit, everything
will sound fine when you play the entire CD from start to finish. However, if the
listener skips to track 2 directly, they may not hear the beginning of
the drum hit.
In most cases, these problems are easily solved by "padding" your
CD tracks a little. That is, move your CD tracks a little
earlier in the time-line so that when the CD player plays back
that track, it has a little wiggle-room before it has to start
playing back. XO Wave automatically pads CD Track Markers
that are created using the Auto Create
feature of the Memory
Locations Manager, but manually created CD Track Markers
should be placed a little to the left of the intended location.
XO Wave uses 1/8 of a second when padding, and this is what we
recommend when placing markers manually.
The best way to correct for these errors is to pad your tracks
and listen to the results on a variety of CD players. Ask
your manufacturer to check the master you send them to make
sure the CD Track Markers are correctly placed and to
contact you if there is a problem.
There are many types of errors that affect the accuracy of the data
encoded on CDs. Surface scratches and dust can cause a
disc to be unreadable, but because the laser that reads data
off the disc is out of focus when it passes through these
imperfections, minor dust and scratches my not impair the
ability to burn or read a disc at all, and a little extra
handling care with your master should help avoid this
More serious, then, is the possibility that the burner, or the disc itself,
is inconsistent with the specifications, or is no longer in
perfect working order. The solution is to use a high quality
CD burner and blank CDs. Despite what some industry groups say,
there is a very real difference between the discs sold at
your local office supply store, and the discs that
should be used for critical mastering. In general, CDs burned on
a computer have lower reflectivity, higher error rates, and other
problems which make errors more likely. When playing back, CD players
are designed to automatically correct for many of these errors and mask others.
Correcting errors is good because it means that
the original data can be recovered, but masking errors is
bad because it means the CD player can't read the data and it is
filling in gaps with made-up data.
The utmost care must be taken to ensure that the burned CDs
are of the highest possible quality to prevent this type of error,
because any uncorrected errors on your master will be passed on
to your manufactured CDs.
Probably the most significant choice you can make when preparing your
CD master is to choose a high quality CD. We discuss this issue
and make some specific recommendations in our FAQ. It is also important
to choose a high-quality CD burner, such as those found in
higher-end desktop computers. Many mastering engineers swear
by Plextor drives, though our
experience is that many drives can produce high quality
results. Generally speaking, it is probably best to avoid
laptop drives for real mastering work, because many compromises
must be made on those systems
for space, power, cost, and other considerations, which generally take
priority over reducing error rates. That does not mean,
however, that you can't produce great results from a laptop --
it just means you may want to be especially careful when
choosing media, and double check your discs to make sure they
sound exactly the way you want.
Once you have a good drive and a good blank, make sure you do what you
can to isolate the burner from power fluctuations and vibrations.
Both problems can cause disc errors, and even a nearby inkjet printer
or sub-woofer may be enough to increase your error rates. Be sure
to isolate your audio equipment electrically using a dedicated
circuit and a high quality UPS or surge suppressor. A high-end
power conditioner is best, and is generally a very good investment for
anybody working in audio.
If your software offers burn verification, as XO Wave does, always be sure
to use it as this will ensure that the data on the CD is
the data you meant to put on the CD. Because of chronological offset,
some software uses techniques for verifying that may ignore silence
on your CD. Though unlikely, it is possible for errors to be missed
because of this. (XO Wave's verification does not ignore silence.)
As important as verification is, it only proves that your master
can be read correctly on your machine, so don't take it for granted
that your CD is fine just because your computer says so -- listen
to it on another CD player or computer (or several) before sending
An increasingly rare issue is so-called "track at once" ("TAO") burning. Some burners
and burning software burn each track separately and "link" them together
in a way that usually works on CD players, but may cause problems
at the mastering plant. Instead, make sure your software
and hardware support "session at once" (sometimes called "disc at once" or "DAO")
burning. If you are using XO Wave, you can rest assured that session
at once burning is being used because XO Wave does not support track
at once burning.
One final thing to consider is so-called "buffer underrun protection", offered
by many CD burners. Buffer underrun protection shuts the laser down
if the burner is not receiving data fast enough, and resumes burning
when the buffer contains enough data. The advantage of buffer underrun protection
is clear: it prevents you from having to start a burn over again with a new
blank CD if your OS or
hard drive is not quite fast enough to keep up with the burner, or is interrupted by another task.
The disadvantage, however, is that the burner generally does
not start up at exactly the same place it left off, and while it may
play back fine, the discrepancy can produce read errors at the manufacturing plant.
This type of problem is insidious because it can be very difficult
to detect. For this reason, XO Wave turns off buffer
underrun protection by default during CD burns.
As long as your computer is relatively fast and you are not overtaxing it
while burning your CDs, this is not an issue, but you can turn it
back on, if you're working on something less critical.
It's a good idea to ask your manufacturer to check over
the disc for things like red book conformance and Block Error
Rates (BLER). This will ensure that your CD master plays
back correctly on their system, and that the data is transfered
without loss. While this applies to all disc burning, it is especially
true if your master may be compromised for some reason (for example,
if you did not use the best blanks or burner, or you didn't
spring for overnight shipping). Don't assume that all is well
with the disc simply because it plays back.
When having your CD manufactured, it is possible that the
finished product will not be exactly what you sent. This can
be for a number of reasons such as poor manufacturing conditions,
incorrect transfer of your master (the worst of these types of
blunder, such as making an analog transfer, seem to be a thing
of the past, thanks to the increasing use of computers)
and chronological offsets, described earlier.
If you are ordering a small run of CDs, they will be
created on a standard CD burner from blank CDs, and may be more
likely to suffer from these problems than higher-volume orders
which should be "pressed" from a glass master. In both cases,
it is the manufacturer's job to ensure that exact duplicates
are made of your CD and nothing less should be expected. When
your shipment arrives, listen to it and compare it with your
master. Listen on several CD players and jump to each track
to make sure that you always hear what you expect. Make sure
the track lengths are the same on your disc and the
manufactured disc. Make sure the "lead-in" or pregap
for each track is the same. If your disc had meta-data,
such as CD Text or ISRC codes, make sure those are present as well.
If there is any difference,
contact your manufacturer immediately.
While ensuring that the finished product is exactly like the
CD you created at home is the manufacturer's responsibility,
communicating your concerns before you send them a master
(and throughout the process)
will help ensure that you get the expected results. Before
you send your master, be sure to find out exactly what they
need, and make sure the disc sounds exactly the way you want it
to. If the manufactured CDs don't sound exactly like the
disc you made at home, be sure to contact
the manufacturer to get the problem fixed right away.