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I
have been surprised at how disappointed some are about the Vetta's Double
Tracker. Some claim that they cannot hear the effect, or that the effect
does not work right. Whether you're a novice or a pro, it has been my
musical experience, that when someone claims they cannot hear a particular
effect, it is simply because their musical ear has not yet developed the
ability to distinguish the effect. And how could anyone say the DT
doesn't work "right" without actually knowing how Line 6
engineers define
"right" according to the intended design. Therefore, it would be unfair to
harshly criticize Line 6 or the Vetta for an effect that one doesn't fully
comprehend.
Now
I'll
be the first to admit, having already understood the recording
production technique of double tracking, what I had envisioned in my head
was going to be this miraculous, 100% accurate simulation, just like it
sounds on a CD effect...but it wasn't. But then again, I realized my expectation was un-realistic,
because no one else has attempted to simulate this effect to this degree in
an amp before. So technically, there was really nothing to compare it to
other than some "ideal" I had floating in my head about how I
thought it was supposed to sound, especially in comparison to real double
tracked guitars.
I
suppose I was really expecting the DT to make a SUPER HUGE difference in the sound,
or make one of the modeled amps sound "exactly" like a separate guitar
player was playing (doubling) a track alongside my playing. After
experimenting with the DT, and thinking
realistically about it...double tracking is a big call to try and reproduce
with DSP (digital signal processing) technology. The sheer fact that the Vetta
comes
as close as it does to simulating double tracking is extremely impressive. And
now that I've worked more with it, I'm so glad the effect was included.
The Double Tracker is another
digital tool in the toolbox that can be used...or not used...but at least
it's an additional tool of choice.
"the
Double Tracker is another digital tool in the toolbox"
For
those who may not already know, "double tracking" is a popular studio technique
which has been
used extensively in most styles of music in order to
create a thicker and more interesting guitar sound and image in the final
mix. This is the process of recording a guitar track, then having the guitarist
record to a second track
while listening to the first and duplicating it. When the two tracks
are played back together, the result is a slight "chorusing"
and fattening of the signal due to minor pitch, timing, and dynamic
(volume) differences
between the two performances. In addition, double tracking helps to create
a "stereo" guitar sound
when those individual tracks are panned to different positions within the
stereo field. And the Vetta works much in the same way. By allowing you to
separately adjust the panning position for both AMP1and AMP2 anywhere in
the stereo-field, from hard-left to hard-right, and applying the Double
Tracker, you can actually create a stereo image that sounds like two
separate guitar tracks.
How
can you accurately simulate a second guitar player or part?
The
reason double tracking works as well as it does in multitrack recording, is because of the inherent
differences that occur when playing the same guitar part
multiple times. I'm not referring to melodic differences, but the subtle performance
differences of: timing, dynamics, and pitch. In the real world, there is just no way to play
the same guitar part twice and have both parts be absolutely identical. So
Line
6 obviously faced a tremendous challenge when they decided to include a
double tracking effect. But how does one go about trying simulate a second guitar player/part
in real time? Answer...with proprietary digital technology...the Vetta
Double Tracker.
Obviously,
it
is extremely challenging to manipulate an incoming guitar signal,
digitally apply aspects of the "human factor"
and mirror what occurs in the real world during a guitar players
performance. You can easily split the incoming guitar signal into separate
paths, but these are still identical clones. Even if you send these cloned
signals to separate amp models, such as the Vetta does, and apply different effects and equalization,
you will still be missing the three most fundamental differences: timing,
dynamics, and pitch. Without these three, tonal differences alone are
still not enough to produce a signal that really simulates studio double tracking.
Let's
take a deeper look into the "major" differences that occur.
TIMING
DIFFERENCES: First, there
is no way to play perfectly in sync with another guitar player or
pre-recorded guitar track. When jumping from chord to chord, or note to
note, there will always be subtle timing differences (in the milliseconds)
occurring that differ each performance. The sloppier your timing is, the more
dissimilar the two guitar parts tend to sound from one another.
DYNAMIC
DIFFERENCES: Second, there
is no way to identically match the picking and strumming dynamics of a
guitar performance. There will
always be times when you strum chords or play notes with varying degrees
of intensity. All those subtle little volume differences add up to
distinguish both parts. Also consider, that different amps, pickups, and strings, all react
differently and will impose their dynamic effect upon the signal as well.
PITCH
DIFFERENCES: And thirdly, there
is no way to have absolute identical pitch occurring at all times. There will
always be micro-differences of pitch occurring between each performance.
Differences of pressure applied against the fretboard, intonation
differences between guitar necks, and differences in string tuning all
play their part in creating pitch differences.
TESTING
PROCEDURE: For
all you tech-heads out there, here's a detailed explanation of how the
testing took place. In order to more accurately determine what kind of
signal processing the DT applies, I thought it best to start with a known
constant. In this case, the known constant was the input test signal,
which was created in Sound Forge to be a "mono" square wave
impulse response, with a set amplitude (volume), a set impulse length
(250ms), and a set duration of
silence (250ms) between each impulse. What this gives you, is an
easy to see waveform that looks similar to bar graph (see illustration
below).
If the DT processes both AMP1 and AMP2, then we should be able to easily
see any changes to our test signal.
 
OBSERVATIONS:
Keeping all the above background theory of
timing, dynamics, and pitch in mind, let's take a look
at the DT's effect upon our test signal. We can draw some
tremendous insights about what is taking place. First, the DT apparently
uses some form of input threshold sensing, because it appears to react to
the incoming signal dependent upon how it sees that incoming signal. Which
amp models you choose, and how you play your guitar will affect the DT
differently. In other words, if you play palm-mutes, or very staccato, or
in a manner that has very distinguishable start and stop times, the DT
appears to look for those small dynamic gaps of near silence and/or
intensity between chords/notes as a trigger mechanism. Long, fluid,
non-dynamic, sustained signals, especially when using the naturally
compressed higher distortion amp models, present fewer instances for the
triggering mechanism, thereby requiring higher parameter settings in order
for the double tracking effect to be more dramatic.
DT
TIMING PARAMETER: The four images below show a close up look of how
the DT's Timing Parameter affects each impulse of our incoming test
signal by applying a randomly changing offset delay to either AMP1 or
AMP2. There appears to be a wide window of offset delay times. And the
Timing Parameter adjusts just how wide this window will be. At lower
settings, the offset delays tend to be between 1ms. and 5ms. As you
increase this parameter, the offset delays can vary anywhere between 1ms.
up to 22ms. and more. I did not try to discover what the maximum offset
delay might be, but as the owner's manual describes, it's enough to make
you think you're playing with a drunk guitarist.
DT
DYNAMIC PARAMETER: The two images below show a close up look of how
the DT's Dynamic Parameter affects each impulse of our incoming test
signal by applying a dynamically fluctuating (semi-polarized?) volume offset to
both AMP1 and AMP2. In more simple terms, it appears that as the DT
applies a volume increase (or decrease) to AMP1, there is an opposing
volume change occurring in AMP2. As you
increase this parameter, the volume differences can become noticeably
greater to the point of sounding very unbalanced and unnatural.
Let
me show you another example. The first image below shows the left and
right output signal of the Vetta with the Double Tracker turned OFF.
Take notice of how the waveforms appear the same. Even though we have
each amp panned hard left and right, because the output signals are
virtually-identical, the sound is MONO, and appears at the very CENTER
of the stereo field.
The
additional image below shows how
the Double Tracker's Dynamic Parameter can affect an incoming guitar signal when
turned up to extreme settings. Once again, take notice of how the DT
applies opposite volume adjustments to both AMP1 and AMP2. As the red
lines indicate, as AMP1 is processed with a volume increase across time,
AMP2 experiences a volume decease. Extreme settings produce very
unnatural and unpleasant volume shifts between the two amp models.
PARAMETER
SETTINGS: The parameter settings for the Double Tracker can really
vary depending upon which amp(s) you decide to use. You can sonically
abuse your output signal by using more extreme settings, so try very
minimum settings when first tweaking the parameters. Using two different
amp models will help to produce more realistic results for stereo
recording. And your style of playing has a direct affect upon how the DT works.
The
TIMING parameter seems to be the most sonically useful. Just one
TIMING knob "click" past OFF is enough to make a noticeable
difference, by subtlety widening the two amps into a stereo image. At
higher settings, the timing differences increase, and produce an even
more distinct stereo image. TIMING settings up to 12 o'clock work best,
and you may find some use for settings above this, but set too high, and
you may find too much "sloppiness" between the two amps. You
may also notice that when using
"identical" amp models and settings panned hard left and
right, the timing differences
that occur between AMP1 and AMP2 cause the signal to jump around in the
stereo field. But keep
in mind, this is typically not the sonic result when two different amp models are
used, and it may be best to actually use two different amp models to
achieve full potential.
The PITCH parameter
simply adds a subtle detuning between the two amp models. Minimum
settings can go unnoticed. The detuning really becomes apparent only at
higher settings.
The
DYNAMIC parameter is the one most difficult to adjust. Minimum
settings up to 9 o'clock seem to work best and sound more natural.
However, if you adjust the setting too high, you will get very unnatural
increases and decreases of volume between the two amps.
FINAL
CONCLUSIONS: The Double Tracker is more easy to recognize while
listening to a playback recording of the Vetta then when you are in the
midst of playing the guitar (with the exception of using an extension
cab). When you are sitting in the
"sweet" spot between studio monitors (or between the Vetta
Combo and a Vetta 212S Extension Cab), the effect is clearly
heard, and impressive enough to appreciate when you get the parameter
settings adjusted properly. Anyone with a good ear and
attention to sonic detail will definitely notice it immediately. But
realistically, how many end users are sitting in front of studio
monitors playing the Vetta direct (with the amps speakers turned off).
Some users may actually be hearing the effects of the DT, but not
recognize the effect depending upon their degree/level of experience
working with stereo signals...and so many guitar amps are mono (with
stereo fx), so many users may be less experienced with the stereo
capabilities of having two configurable amp models.
I'll
be the first to say that the Double Tracker may not be distinctly
recognized if you are playing "only" through the Vetta Combo's
speakers, this is simply due to the fact that the amps speakers are
located so close to each other, and the listener is surrounded with
sound. However, the effect becomes much more distinct when recording
from the DIRECT OUTPUTS while listening to playback on studio
monitors...you are able to point to an
exact location in the stereo-field from where the sound of each amp
originates, and hear the timing, dynamic, and pitch differences.
And
the DT can sound downright awesome when using the Vetta 212S Extension
Cab (or any additional extension cab) to actually create some physical space
between the amp models when they are panned hard left and right. Having
an additional Extension Cab is the "only" and best way to
compliment the Vetta Combo so you can hear the full potential of sound
that it is capable of producing. An Extension Cab provides for a very
wide "stereo" separation of the amp models, because the Vetta
Combo is handling the LEFT side of the stereo outputs, and the Ext.Cab
is handling the RIGHT.
With the right settings, the Double Tracker can be
used most
effectively with both direct recording and live performance. The DT can produce some fantastic stereo results provided you have the
parameters adjusted to optimize the effect for whichever amp model(s)
you decide to use. Used in the home recording studio, it can
really sound very similar to a double tracked guitar. Used on stage, it can add a
"wide" 3-dimensional quality to the sound...especially if you
are using the PING PONG DELAY which will jump between the cabs
LEFT-RIGHT-LEFT-RIGHT etc. Can it accurately
re-create a double tracked guitar 100%...almost. The technology is there
and can only get better over time. Line 6 has created a winner effect in
my book, and I look forward to the day when their digital technology
reaches the point of completely fooling out sonic senses.
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