Tiptop Audio - Time Fabric (Z-DSP card)
This collection of Pitch Programs for the Tiptop Audio Z-DSP module use a pitch shifting algorithm
much like the earliest digital pitch shifters released. Sounds similar to the Eventide H910,
AMS 15-80 (with Pitch board) and Publison DHM 89 can be achieved. These programs are
intended more for pure eects rather than the complex multiple harmony lines later devices
and plugins became known for producing. Chords from single VCOs can easily be made using
the ‘Interval’ programs on the card though.
Pitch shifting in the Z-DSP uses a technique called ‘rotating tape head’ delay lines named after
pioneering tape based experiments in Germany in the 1960s. The tape heads move at speeds
independent of the tape playback path and two heads are crossfaded to make a continuous
output. Much of Karlheinz Stockhausen’s output of that era heavily (ab)uses the two tape
machine method of changing pitch. Digital memory and processing allows the same method
by manipulating two playback positions in memory and crossfading them using DSP. This is a
fairly primitive process compared to what can be done today using FFTs (phase vocoder) and
Time Compression and Expansion, but there is a certain sound associated with it that is undeniably
The programs are intended more for pure effects than complex multiple harmony lines. For instance you can create chords from a VCO signal.
The technlology used can be compared to a reel-to-reel tape machine with tape heads moving with at different speeds than the tape itself and where two tape heads are crossfaded.
The first six programs' algorithms looks like that:
left in -> pitch shifter -> delay line -> left output -> [analog feedback to left in]
right in -> pitch shifter -> delay line -> right output -> [analog feedback to right in]
The differences are in their controls with different ranges. The delay times are ca. 500ms for the left channel and ca. 250ms for the right one.
- Dual Pitch Shifter: shifts +/-1 octave. Delay time left <500ms, delay time <250ms.
- Dual Delay Shifter: Like program 1 but with individual delay time control per channel.
- Interval Shifter 1: semitone quantized pitch shifting with identical intervals for both channels.
- Interval Shifter 2: semitone quantized pitch shifting. Left pitches up, right pitches down.
- Dual Micro Shift. Microtonal pitch shifting by +/-1 semitone. Common control of delay time for L & R.
- Dual Delay Micro Shift. Like program 5 but with individual delay time per channel.
- Pitch -> Delay. Pitch shifter before the delay. Feedback taps the delay output only
- Delay -> Pitch. Delay before the pitch shifter. Feedback taps the delay output only.