Radial Tonebone PZ-Pre Acoustic Preamp 2 Chnl w/EQ-PSU

It all starts with great tone!

As with all Radial products, all efforts have been made to ensure the very best and natural transfer of the instrument’s tone is maintained. The PZ-Pre features 100% discreet class-A piezo boost circuitry (PZB) to provide the most musical transfer plus a high efficiency preamp designed reduce distortion and noise while maximizing headroom.

Inputs:
There are two inputs on the PZ-Pre. Each of these may be used independently for two instruments or combined using the blend (mix) function. These can be used with instruments equipped with a built-in preamp such as an acoustic-electric guitar or using an external buffer from a piezo type source.

Input select:
The instrument select footswitch lets you chose which instrument is active by selecting the input channel. Adjusting the level controls lets you control the level for each instrument or pickup and balance the tone as needed.

PZB boosters:
Each input is also equipped with a piezo booster (PZB) that allows a low output pickup such as a piezo electric element to be connected without the use of an external preamp. The ultra-high fidelity of the class-A piezo booster coupled with the high 10 meg ohm input impedance assures you get the best signal transfer without distortion or degradation.

Blend:
The blend allows you to accept two sources and mix the two channels together. This is a welcome addition for instruments that may have two pickups built-in or when combining two sound sources. You can even have two guitarists connected at the same time for a jam!

High-pass filter:
Acoustic instruments are notorious for on-stage feedback and runaway resonance. A three position high-pass filter (which means that it reduces the low frequencies) is extremely effective at getting rid of runaway resonance which often causes harmonics to feedback. This also serves to get rid of low end rumble that can cause a mix to sound muddy.

Notch filter:
The size of the instrument determines its tone and resonance, which in turn can cause feedback. This is addressed by providing a variable notch filter with two different Q's or notch depths that lets you dial in the offending frequency and eliminate run-away feedback.

Semi-parametric EQ:
Once again, since all instruments are different, the PZ-Pre’s tone shaping has been designed to address the various characters with a 3-nand EQ and semi-parametric mid range control. This simple yet highly effective EQ is lets you dial in the sweet-spot for the most natural and dynamic tone.

180º Phase reverse:
Technically speaking, this is actually a polarity reverse switch that lets you control the internal polarity of the signal path before it reaches your on-stage amp. It is used to help reduce feedback on stage when the physical location of the performer, the monitors and the stage amp coincide to cause a feedback hot-spot.

Power Booster:
This foot switch lets you activate the power booster for soloing or add-in effects using the inserts send & receive jacks. For instance, you could add a chorus and slight boost for a passage. The power booster assign switch lets you assign the boost footswitch to activate the power booster, the effects loop or both. Adjust the power boost level to suit!

Mute and tuner out:
A mute switch lets you easily silence all of the outputs except the tuner out for quiet tuning on stage. The tuner output is separately buffered so that it does not load the pickup or allow tuner clocking circuit to cause noise.

Instrument out:
This is a buffered output that is designed to drive an on-stage amplifier.

Balanced DI outputs:
The PZ-Pre is equipped with two direct boxes: one is pre-effect, pre-EQ that sends the unprocessed instrument signal to the PA system to allow the house engineer to set the tone for the room. The second is post-effect, post-EQ for on-stage wedge monitors or in-ears. This is used when you want to send ‘your’ sound to the PA system.

Although absolutely jammed with features, the Radial PZ-Pre is actually very easy to use. To begin, as always make sure the equipment you are connecting is either turned off or the volumes set to zero. This will eliminate any turn-on or connection transients from harming the electronics or speakers.

Begin by connecting the PZ-Pre power supply. The 15VDC supply is included with your purchase in the correct voltage for your country. The LED on the input channel will illuminate to let you know power is connected. Using the input select switch, ensure input A is active. Begin by setting all of the controls ‘flat’ to 12 o’clock and switches in ‘bypass’ as shown here. You will also want to make sure the boost and mute switches or off (LED off). We are now ready to make the connections.

Input options

There are two inputs on the PZ-Pre for two instruments. Each is equipped with its own PZB piezo booster circuit. If you are using the PZ-Pre with a contact pickup, you will likely want to turn the PZB booster on. This switch is recessed to avoid accidentally turning the PZB on or off as the turn-on transient could create a loud ‘pop’ which could damage your speakers. Pushing the PZB switch IN will active the boost circuit. If you are using a magnetic pickup, you should first try the unit without the PZB to see if the output level from the pickup is sufficient. For instruments with built-in electronics such as an electric violin or acoustic guitar, the PZB would be left in the out position. Connect your instruments.

Sometimes, you may want to have both input channels on the PZ-Pre active at one time. This could be for a jam session with two guitars or more likely; it could be for an instrument with two transducers such as one inside the acoustic cavity and the other outside near the bridge.

By depressing the recessed MIX switch, the toggle footswitch will be defeated and both channels will be on at the same time. You can then feed the inputs with any form of source and then blend the two signals using the two level controls. The PZ-Pre is not equipped with any form of phantom or power to supply a remote microphone, so this must be powered independently.

Once you have found the balance, try adjusting the EQ and filters as described here to find the tonal balance that works best. When using multiple sources, you are creating a complex tone that may take some practice to get just right. Take your time, experiment and have fun!

Output options

There are 4 different outputs on the PZ-Pre:
1. Instrument amp output – used for your personal stage amplifier, this is a high impedance guitar or instrument level signal. Connect using a standard coaxial guitar cable

2. Tuner output – works with the mute footswitch for quiet tuning on stage. If you have a tuner, you would connect it here using a short instrument cable. Muting the signal will turn off all of the outputs except the tuner out which is active at all times.

3. The pre EQ, pre-effects output – this low impedance balanced XLR output is generally sent to the main PA mixer and is generally used when you have a sound engineer doing the mix. Like all direct boxes, it is mic level and therefore should be connected to a mic preamp. This output sends the ‘dry’ signal to the PA without being affected by the tone controls or effects on the PZ-Pre. This allows the FOH (front-of-house) engineer to adjust the tone and effects as needed for the room sound.

4. The post EQ, post effects output – is also a balanced mic level output but this time, the signal includes all of the EQ settings and effects (if used) on the PZ-Pre. In a large scale concert production, this output would generally feed the stage monitors with your ‘wet’ sound. It would also be the preferred output to the PA in show clubs where you may want to send your sound to the house mix.

You are now set to connect the outputs. Now turn up your amp and PA system to make sure you are getting signal. If you are also using monitors, you should now turn these on. It is good practice to always do you initial sound tests at low volume. Increase the input level to where you feel it is comfortable.

Setting the EQ

You are now ready to experiment with the tone controls. Start by adjusting the low and high controls and then work on the mid range. Keep in mind that feedback is generated by excessive resonance and adding bass on a loud stage can cause your instrument to vibrate, resonate and ‘feed’ back into the PA causing a run-away feedback loop. The PZ-Pre’s powerful EQ is designed with plenty of swing so small changes will have a big impact on your sound! Remember rule no.1 in audio: With EQ, least is best!

Another important fact is that all of the personality and energy in an acoustic instrument is found in the mid range. This is also where human hearing is most sensitive. So if you cut the midrange out of your signal because it sounds nice when you play alone, you will no longer be heard in the mix when you play with a band.

The midrange controls on the PZ-Pre include a frequency knob and cut & boost knob. Most acoustic instruments tend to favour a minor midrange cut: try setting the mid control to 11 o’clock and rotate the frequency control until you find the sweet spot. There are no rules, just use your ears and remember… least is best!

Controlling feedback

Once your tone has been adjusted, try increasing the level to the point where the instrument begins to resonate or cause feedback. If low resonance is encountered, try activating the low frequency roll-off (high-pass filter) and setting it to the first position. This setting will give you a gentle roll-off that will usually tame run-away bass resonance.

Next, you may encounter mid-range or high frequency squeal. This is best controlled using the notch filter. A notch filter is basically a type of EQ with a very narrow Q or notch that cuts out the center frequency as set by the notch control. There are two settings for normal and extra deep notches. Simply select the first notch setting and slowly sweep the notch center frequency control until you locate the offending frequency. This control extends over a wide range from 56Hz to 330Hz If you find that the normal notch is not sufficient to suppress the problem frequency, try extending the filter by going to the deep position.

In some instances, as you move around the stage you will notice that feedback or resonance seems to increase in certain spots between the wedge monitor and your personal amp. This is caused by nodes either amplifying each other or cancelling each other out at various frequencies. Try reversing the (absolute) phase with the 180º polarity reverse. This can often help minimize this occurrence. Keep in mind that the louder you set the on-stage volume, the greater the occurrence of feedback or resonance will be. This is a fact of life when trying to amplify acoustic instruments.

Adding effects and power booster

Once your main sound is set, you can now begin to add effects such as chorus or reverb in the effects loop and play with the power booster for soloing. The PZ-Pre’s power booster will generate up to 8dB of additional gain. This should be plenty for soloing. Be careful! The powerful booster will augment your level to a point where it could introduce feedback! So try increasing small bits at a time!

You can also add effects using the effects loop on the PZ-Pre. You may want some of these effects to be sent to the PA system while you may only want some to go to your stage amp. For instance adding a chorus pedal to your acoustic guitar is likely an effect that you will want sent to the PA system while adding reverb may be an effect you only want to ad to your on-stage amplifier.

These of course are all based on personal preference and technical requirements based on the size and complexity of your sound system. Standard coaxial instrument cables are used to connect the effects going from the ‘send’ jack on the PZ-Pre to your effects and then back via the ‘return’ jack.

The PZ-Pre effects loop is turned on using the boost footswitch and is activated by selecting the ‘loop’ or ‘both’ using the footswitch assign switch. If you do not need a power booster, you could dedicate the effects loop for your effects only. You can also use the power booster as a ‘gain make-up’ for effects that may need more punch by setting the switch to both. You can also add a delay, fuzz and chorus and boost the signal for an avant-garde electric violin solo without having to tap-dance to create the effect. One foot-stomp and everything goes on!

Eliminating hum, buzz and system noise

The PZ-Pre internal electronics employ what is called a ‘virtual ground’ whereby we create a internal ground for the safe operation much like an airplane. (Ever notice there are no ground wires connected to airplanes and they seem to work just fine?) But as soon as the PZ-Pre is connected to your stage amplifier or to the PA system, it acts like a bridge and connects all of these electrically charged devices together. This can lead to stray currents working their way into the sound system.

The PZ-Pre is equipped with a ground lift switch for the XLR outputs. If you encounter buzz and hum, try depressing the ground lift switch as this often will help. There is also a second 180º polarity reverse switch on the main PA output that is designed to help reduce stage feedback or reverse the electrical polarity on the XLR when using the PZ-Pre with older pre-AES standard equipment. (AES = Audio Engineering Society standard is Pin-1 ground, pin-2 hot).

PZ-Pre Setup:

The PZ-Pre is more than just a sonically pure acoustic instrument preamp... much more. It's an amazingly versatile on-stage control center for your acoustic rig! As illustrated here, the green arrows show the two independent instrument input channels and the effects receive jack. The red arrows show the outputs, including the stage amplifier output, dedicated tuner out, pre-EQ balanced out, post-EQ balanced out and FX loop send. The three footwitches let you effortlessly toggle between instruments, bring in boost and/or effects and mute the output for quiet tuning. Set the recessed Peizo buffer switches to suit your instrument's requirements, then adjust separate levels to balance them. Lo-cut, Notch filters, parametric EQ and boost level controls allow the perfect fine-tuning of all parameters of your sound.