Bobby’s Time Machine
a stereo delay inspired by the early digital age
What is Bobby’s Time Machine?
Bobby’s Time Machine is a rackmount (3U) digital delay I built with the intention of capturing the essence, character and creative limitations of a rackmount delay from the dawn of the digital age, but with modern capabilities. This machine was primarily inspired by the Lexicon Primetime Model 93, to which I owe a great deal of gratitude. The Primetime was originally released in 1978 and was one of, if not the first delays to feature a repeat hold function and sample rate control. Meaning that when repeat hold is engaged, the audio repeats continue indefinitely until disengaged. Bobby’s Time Machine contains this same ability with the “feedback hold” button as well as control over the sample rate to which audio is processed. This allows for extremely unique timbre control and the ability to use the machine as its own instrument in live performances. It contains the following features:
Input stage, two separate input preamps with adjustable gain (from -∞dB up to +20dB) with the ability to normal the left input to the right input or keep them both separate.
Delay lines, two separate high quality (96kHz 24bit) digital delay lines with independent controls for time, feedback, dry and wet mix.
Feedback control, contains controls over feedback hold, delay line recording on/off toggle and sample rate.
Recirculation filter, a resonant digital low-pass filter applied to the wet signal with separate controls over the filter cutoff frequency for each channel, a shared control for resonance and an on/off toggle button for quickly switching on/off high feedback.
Modulation, contains a digital LFO internally connected to the delay times for pitch modulation. Contains separate controls for each channel’s modulation depth and a shared modulation rate control, as well as a toggle button to switch between different waveforms (sine, square, sawtooth and triangle).
Output filter, a resonant digital filter applied to both the wet and dry signals before the output stage. This filter can be configured to be a low-pass, high-pass or band-pass filter. It contains shared controls for cutoff frequency, resonance intensity and a knob to change the mode.
Output stage, contains controls to attenuate each channel and either mix them together or be output separately.
Control Voltage, nearly every single parameter on this machine can be controlled via eurorack control voltage signals. The digital LFO from the modulation section can also be routed out of the machine and be used to modulate any of the CV controllable parameters. All of the CV controllable parameters are the following:
Separately controllable parameters: left and right channel delay time, feedback, dry level, wet level and recirculation filter cutoff frequency
Shared control parameters: output filter cutoff frequency, output filter resonance, recirculation filter resonance and internal LFO frequency.
Trig/gate inputs: sample rate up, sample rate down and feedback hold.
