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 be.

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.

Feedback Control

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 beast.

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 eliminating’ surgery!

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.

Physical construction

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!