Recording - March 2013 - 23

expense, or if you prefer to skip the headache of trying to perform the perfect build yourself, a DAW builder is probably the
right choice for you.
We don’t have any articles on DIY Windows machines or on DAW
builders up on our website, mainly because most advice we can give
in those areas becomes obsolete over time (necessitating articles like
this one!). I can state that at least one DAW builder whose products
have been reviewed by me in our pages, ADK Pro Audio
(www.adkproaudio.com, not to be confused with ADK the mic manufacturer at adkmic.com), is still in business and going strong.

might be provided with your system, it is usually far less CPU efficient. If no ASIO driver is available for your audio interface in the
host, a program called ASIO4ALL (www.asio4all.com) can be
tried instead. While not as efficient as a dedicated ASIO driver
directly from the interface manufacturer, it’s still a better alternative
than the DirectX or non-ASIO drivers for your DAW.
Once the drivers are installed, it’s time to configure your buffer
settings. This setting, if set too low, can be one of the biggest causes of pops and clicks in your plug-ins. But what is this buffer and
latency mumbo-jumbo really all about? Let’s investigate.

By Devon Brent

3. Buy a general-purpose PC and configure it
This last option is to buy a PC from one of the big box vendors
or other computer stores that assemble general-purpose PCs for
you. The biggest risk here is knowing if the machine will support
what you want it to do, and whether their tech support will be
able to help you at all if you run into plug-in specific problems.
If this is the path you wish to take, the first thing I always recommend is to check into the specifics
of the return policy. Better yet, see if
you can check out a few of the things
I’m describing later in this article,
right at the store before you even
make the purchase. However, if that’s
not possible, the return policy is your
lifeline to protect your bottom line.

After the purchase
Now that you’re sitting in front of
your new PC, looking at the desktop
of Windows 7, it’s time to dig in and
figure out what audio-related issues
you may have. While that new CPU
certainly has the grunt to stream your
plug-ins, that doesn’t mean everything will be smooth sailing. Pops
and clicks may occur with your audio, either all the time, or only
under a certain CPU load or at certain intervals.
These problems usually stem from an audio buffer that’s set too
low, a device or devices inside your PC causing DPC latency
spikes (see below), a configuration
issue within the OS, or poorly coded
drivers for your hardware. Some general tweaks that haven’t been applied
yet to your new system can provide
relief when it is straining from all
those plug-ins you’ve activated.
Let’s look at the more common
hardware and software configuration problems and how to troubleshoot and hopefully solve them.
Audio drivers, ASIO
When given the option on
Windows, the best driver choice for
use with your audio interface is the
ASIO (Audio Stream Input/Output, a
driver standard created by Steinberg)
driver provided by the manufacturer
of your audio interface. While a
generic ASIO DirectX audio driver

Buffers and latency
Just so we’re clear, the terms buffer and latency, while often used
interchangeably, are two separate things. A buffer is essentially a
“bucket” that fills up and holds data to be processed “some time”
in the future. Latency is the actual time it takes from the start of a
process until the results are complete for that particular task.
An ASIO driver uses a dual buffer system for playback of audio;
are two buffers
1 thereyou choose. Oneof equal size, a
size
buffer is actively playing back the audio you’re hearing, while the other buffer is being
filled up in preparation for playback.
Once the first playback buffer is done
playing, the second buffer has to be
full and ready for playback. If it isn’t,
you get a click or pop.
Now, buffer size is set in samples
(64, 128, 256, etc.); at a given sample rate, doubling your buffer size
means that it takes twice as long to
play back what’s in the buffer. The
time it takes to play one buffer-full of
audio is the time gap between
putting audio into the DAW and getting it out—we call this the latency.
To calculate how much time it will
take to completely fill or play back the buffer’s contents, you take the
number of samples for the selected buffer size and divide it by the sample rate. For example, 256 samples with 44.1 kHz sample rate
(256/44100) provides a latency of about 5.8 milliseconds (thousandths of a second). You can cut laten2 cy down by shrinking the buffer size at
the same sample rate: 128 samples
divided by 44.1 kHz is about 2.9 ms.
Or you can cut latency down by boosting the sample rate: 256 samples with
a 96 kHz sample rate (256/96000) is
roughly 2.7 ms of latency.
As you can see, the higher the sample rate or the smaller the buffer, the
shorter the time the CPU has to do the
job of filling the buffer. So lower
latencies mean higher strain on your
CPU, even if the buffer being filled is
smaller. Lower latency, more CPU
load... higher latency, less CPU load.
Keep in mind also that even if a
buffer setting is available for you to
choose, it doesn’t mean your machine
is powerful enough to keep up with that
buffer choice and produce click-free
RECORDING March 2013

http://www.asio4all.com http://www.adkproaudio.com http://www.adkmic.com

Recording - March 2013

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