Piezo pickups inherently
produce a very low output and require a very high
input impedance to produce a well balanced tone.
Over the past 30 years, these have evolved whereby
most acoustic guitars have built-in active electronics
to buffer the signal while providing the player
with control over tone, level and sometimes feedback.
But even these wonderful devices are limited by
compromise. For instance, batteries work fine,
but when subjected to a serious, non-stop task,
they quickly run low and discharge. Ask any audiophile
and they will tell you: ‘class-A circuitry
sound best’. Unfortunately, class-A circuits
are inefficient which means that they cannot functionally
be used with batteries. So guitar pickup manufacturers
are left with little choice but to build their
piezo preamps using more efficient class-AB circuit
topologies and the tone purest suffers the result.
The up-side to class-AB designs is that they can
provide greater headroom with less current. It
seemed clear: the only way to achieve great sound
would be to develop a proprietary class-A circuit
for the PZ-Pre front end and then employ class-AB
for the preamp stage. This way, the PZ-Pre could
at once handle off-the shelf instruments and be
able to provide the needed boost for the piezo
systems to run properly.
Another interesting phenomenon is the advent
of the collector guitar: 25 years ago, professional
musicians thought nothing about cutting a whole
in their guitar to fit a pickup or internal preamp
as this was the only way to get the job done.
Today, this is paramount to sacrilege! No one
would dare cut a hole in a 1968 Martin for fear
of eroding the instrument’s value. This
same applies to vintage violins, hand crafted
cellos or on old Kentucky mandolin. The good news
is the wealth of low-cost yet good sounding ‘affordable’
instruments means that musicians can now put their
favourite instruments away behind glass cases,
and never, ever use them for fear of… wait
a minute! Isn’t playing your great instrument
the whole point of owning one? This seemed to
point to a new reality: great players want to
use their favourite instruments on stage. This
meant that the PZ-Pre had to be able to both handle
typical active acoustic guitars and be equipped
replace the internal instrument preamp if need
The instrument channels
Most performers, whether they play acoustic guitar
or mandolin, tend to have two instruments on stage.
The second instrument is often for backup should
a string break; in some cases it may be tuned
differently; maybe it is has a completely different
output level; or it may even be a completely different
instrument! The PZ-Pre is equipped with two inputs
to address these needs and each input features
a separate volume control to match the levels.
Today, most acoustic guitars used on stage have
preamps (buffers) built in that can send a strong
signal to a guitar amp or direct box. For instruments
that do not have a built in buffer, a separate
piezo booster may be engaged on each channel that
both alters the impedance and increases the level
to properly interface with these types of pickups.
The flexible design means that a bluegrass player
can switch between a guitar and mandolin by simply
stomping on a footswitch. More importantly, for
those that like to perform using their favourite
vintage instrument, they do not have to cut a
hole into the body to fit the preamp as they can
use a contact pickup and PZ-Pre to achieve the
same effect. In fact, during listening tests we
found that a great contact pickup used in tandem
with the high performance preamps stages in the
PZ-Pre completely outperformed the preamps in
most acoustic guitars.
Acoustic instruments, whether a guitar, mandolin
or contrabass, all resonate at different frequencies
that can cause feedback. Anyone who has played
live knows that when you turn the volume up, acoustic
instruments are prone to howling, whistling and
runaway low frequency resonance. This is generally
caused by the on-stage monitors or personal guitar
amp causing the body or top of the instrument
to start vibrating, creating a resonant feedback
loop. To address the problem, we introduced several
tone shaping and resonance eliminating controls
that work in tandem to help tame the feedback
The first is a low cut control – technically
called a high-pass filter (lets the highs pass
while cutting the lows). Odd as it may sound,
the high-pass filter is in fact one of the most
powerful and functional controls on the PZ-Pre
to eliminate feedback. It is well known that if
you can control the fundamental frequency, the
upper cascade of harmonics will often follow suit.
Next is the notch filter. This is an ultra narrow-band
‘cut only’ EQ that is used to find
an offending feedback or resonance and surgically
remove it without affecting the instrument’s
natural tone. This is accomplished with a choice
of two narrow V notch filters and variable center
frequency control. These narrow band filters enable
the user to dial in the precise resonating feedback
point and apply minor or major ‘feedback
Finally, as you move around on stage, you can
often find a position where all of a sudden everything
sounds amazing! Then, you move a few feet over
and it seems like you are overwhelmed with feedback!
This ‘positional’ effect is caused
by the various speakers such as the PA, monitors
and instrument amp and the room acoustics working
together or at odds creating reinforcing nodes.
To help control this effect, a 180º polarity
reverse switch has been included.
Adjusting the instrument’s tone
Every instrument has its own distinct tone. This
meant that the PZ-Pre had to have an EQ on board
that would allow enough control to adapt to various
instruments while remaining very musical. Full
parametric EQ's are very powerful but are both
difficult to use and more often than not, end
up sounding bad. The best sounding and easiest
EQ's to use are standard shelving type used on
most high-end professional mixing consoles. These
are quick to set up and highly effective. Add
a semi-parametric midrange control and you can
easily dial-in the sweet spot to make any instrument
sound warm and natural.
But don’t be fooled by the simple 3 band
design; the PZ-Pre’s on-board EQ is extremely
powerful! Small changes produce dramatic effects.
We follow the ‘least us best’ rule
whereby minimal EQ settings will generally produce
the best results. The mid-range is particularly
important as more often than not, the tonal character
of the instrument is most defined in the mid range
or the ‘body’ of the instrument, so
restraint is definitely the imperative here.
Adding flavour to the mix!
Once the tone and levels have been dialed-in,
you can bet that every self-respecting bouzouki
player will want to add effects and boost his
signal for a solo. A power booster was a definite
must. Then of course an effects loop that could
be engaged using a footswitch. To conserve space,
we combined these. The boost footswitch is equipped
with a 3 position switch that can be assigned
to turn on the effects loop, the power booster
or both. The effects loop send and return jacks
are designed to be used with standard guitar effects
pedals such as reverb, chorus or delay. This can
be combined with the power booster to create dynamic
passages or avant-garde effects.
How many outputs are needed?
Good question… let’s see: the musician
often uses an amp on stage so a regular guitar
level output would be needed. Then there is the
on-stage monitoring system. Today, this can be
anything from a wedge monitor to a personal in-ear
system. Then of course there is the PA System.
And don’t forget the tuner out… This
is just about the precise moment that the engineering
department tosses up the drawings in the air and
exclaims: ‘There is no room!”
But why so many different outputs? Well, each
output actually addresses a different requirement.
In fact, you really have to think of the outputs
in terms of 3 zones. There is the musician’s
personal sound where one would create a comfort
zone on stage. Then the stage monitors: this is
the sound that all of the musicians on stage will
share and finally, the house sound or the sound
in the venue being produced by the PA system.
Most folks do not realize that these are all
very different. For example, you may want reverb
on stage but if you are playing in a hockey arena,
the last thing you need is more reverb in the
house mix! This led us to incorporate two balanced
DI outputs: one for the stage that would be wet
or contain the tone changes, effects and so on
while the other would be dry or be pre-EQ and
pre effects. This would allow the front of house
engineer to adjust the tone as needed and introduce
the effects where and when required.
We then thought about tuning and this meant we
had to provide some form of mute switch plus a
tuner out that when engaged would shut off all
of the outputs and allow the musician to quietly
tune on stage.
Finally, we hade to decide how big the PZ-Pre
should be: During its development, we consulted
with a wide variety of musicians and time and
time again, folks ask us to make it small! This
refrain was echoed loudest by contrabass players
that carry 6 foot tall instruments… go figure.
What they were saying is that today, corporate
gigs can be across town on across the continent.
They want solutions that can fly in a gig bag.
The PZ-Pre had to be compact. And trying to get
all of the features that we wanted into the PZ-Pre
ended up being a real challenge. But after months
of trial, tests, errors and revisions, we finally
got it right.
The PZ-Pre, a powerful tool designed to make
music easy and fun!