Tiptop Audio ZDSP Spring Waves Card

The Spring Waves cartridge also features two unique Spring models. This model calculates
at the sampling rate all of the Newtonian forces controlling the behaviour of a mass-spring
system, and takes into account the following factors: the spring itself and its return force
(with a potentially non linear behaviour), a point where one side of the spring is attached,
a mass attached on the other side, fluid friction (potentially non linear) depending on the
speed of the mobile mass, mechanical limits (a physical spring can’t stretch out infinitely)
and static and dynamic frictions (friction due to the contact with a rough surface).
The audio input is used either to “move” the point where one side of the spring is attached,
or as force directly applied to the moving mass on the other side. The audio output is directly
provided by the motion of the moving mass.

How it works:
In the context of the Z-DSP, the FV1 chip (its brain) computes these physical modeling algorithms.
Physical modeling is known to have heavy CPU consumption, but, despite its limited power, the
nice design of the chip allows running up to four waveguide lines or one spring model, with optimised
code.

For waveguides, the one second delay line is split in 2 to 4 parts and necessary lowpass and DC-cut
filters are inserted in each feedback loop. The rest of the code manages the connections between
the waveguide lines and the controls. When used as effects, as it is the case for Z-DSP, waveguides
can be used in different ways:
– input very short sound burst or impulse and let the waveguide ring, with low damping
(controlling the tuning and additional parameters). A variant is of course to use drum
sounds as input. Very interesting results can also be obtained using sequences. For drums
and sequences, the damping needs to be lowered to fit the BPM.
– input a continuous sound (with a not too high level to avoid clipping) and use the wave
guide as a resonator. This can even give very nice results processing an instrument track or
even a voice. In this case the damping needs to be quite high.

For the spring model, the whole program is dedicated to arithmetics to calculate all the newtonian
forces and their consequences on the motion (and resulting sound). As only one spring can be run
by the FV-1, the more spontaneous way to use it as a filter, but, like the waveguide, you can also
input a short audio burst to make it ring or use it as a resonator.

Controls:

For the waveguide models, the first six programs have common controls:
– Left and right inputs can be used the same way
– Control 1 is defining the pitch of the waveguide (low frequencies on the right). Note that
for programs 1 and 2, control 3 is also for pitch since control 1 sets the pitch for one half of
the waveguide lines and control 3 the other half.
– Control 2 is damping (low damping, meaning longer ringing, is clockwise).

For the spring models, the last two programs have common controls:
– The Left input is the “regular” input and is moving the point the spring is attached to (the
output will be the resulting end position of the spring where le “Mass” is attached)
– The Right input is an “alternate” input that is going to be used as a force directly applied
to the moving mass (be careful with low frequencies ….). This input needs to remain at a
very low level.
– Control 1 is always the hardness of the spring (thus determining the force that will bring
the mass to the center point). You can compare its behaviour a bit to the frequency
control of a regular filter.
– Control 3 is always the Fluid Friction, that will slow the moving mass (the friction depends
on speed). You can compare its behaviour a bit to the the resonance control of a regular
filter, but here low friction means high resonance.