Z-Mode effects on String Vibrations

Z-Mode is a unique feature of the Audere preamp which changes how the vibrating strings are damped.

Your guitar pickups are small electrical generators. They extract mechanical energy from the vibrating string and generate an electrical output. You may think you do not want to extract any energy from your strings as they vibrate but it's not that simple.

Pluck a string – the string will vibrate for some period of time as it decays and then stops. What makes each bass different from the next is how the string’s vibration changes over time, from when you initially supplied the energy from your hand to the string until the string stops vibrating. This is also true of all basses including acoustic instruments, in which case more of the string energy goes into vibrating the top (so you can hear the instrument) as opposed to some going into the pickups.

The electrical parts connected to the pickup create 2 types of load.
The first type of load is resistive and the 2nd is capacitive.
Impedance is the technical term for the combined effects of all electrical loads at a selected frequency.

The Audere preamp lets you select the impedance load placed against the pickups with a flip of the Z-Mode switch.

High Z-Mode is a light resistance load combined with a variable sized capacitance load,
Low Z-Mode has a high resistance load,
Mid Z-mode is a medium resistance load.

The Mid Z-Mode is the sound you are used to in a passive bass with a normal length output cable. The resistance placed against the pickup creates an environment where almost all string vibrating frequencies of interest (at least for bass players) see the same amount of loading and dampen at the same rate.

Low Z-Mode extracts more energy per unit of time from the string. In this mode high frequency vibrations decay faster than the low frequency vibrations. This gives the bass a strong fundamental note follow-on, but the higher frequencies are there at the start of the note to more precisely define the note’s timing. This unique feature of the Audere preamp would not be possible to implement in a passive bass because the generated signal would be too small.

High Z-Mode extracts the least energy from the string per unit of time. Depending on how the specific pickup is constructed, there is a specific range of high frequencies that are dampened at a slower rate than the others, which means their amplitude is higher - this is at the resonant frequency of the pickups. The Audere preamp offers a unique mechanism to adjust what frequency this occurs at. It is this peak frequency range that gives the High Z-Mode its bite.

In the end, what makes the Audere preamp with Z-Mode so cool is that you can select the impedance load, which alters the decay rate of the string vibration.

Link to Technical details and Graphs illustrating the effect of changing the impedance load

Additional technical details on the High Z-Mode:
In High Z-Mode the resistance part of the loading is very light. The major parts of a pickup are a magnet and a coil of wire. This coil of wire is an electrical device called an inductor. Inductors absorb electrical current and generate a magnetic field or visa versa. The coil also contains a capacitive element. The construction of the wire coil creates a capacitor because the wire is coated by a thin insulator. Capacitors absorb electrical current and generate internal electric fields or visa versa. At some frequency (normally in the 3-10 KHz range) the inductance and capacitance of the pickup will allow the energy to transfer back and forth between the magnetic field and electrical field with very little energy loss. This results in a higher amplitude and slower damping at this resonant frequency. For players, this creates a bright aggressive tone in the treble region. Since the location of the resonant frequency will vary based on the pickup’s internal construction, we include the ability to add an additional capacitive element to the pickup load. As you add capacitance, the location of the resonant frequency will move to a lower frequency. The ideal location of this peak is just player specific… no rights or wrongs – a matter of preference.