Pittsburgh Modular - Analog Delay Unit
The Analog Delay Unit is based on the design created for the Voltage Lab synthesizer module. A finely tuned circuit designed to enhance the source material by adding depth and warmth.
The Analog Delay utilizes a pair of 4,096 stage BBD chips to produce a voltage controllable analog delay signal. Clean delay time can vary from 16ms to 340ms. The maximum delay time can be increased using the TIME CV INPUT delay time maxes out at 465ms but the increased time comes at the cost of fidelity and a bit of high frequency clock noise bleed. The name BBD stands for bucket brigade device in reference to a line of people passing buckets of water to quickly extinguish a fire. Each stage of a BBD chip contains a single capacitor. Pairing two chips together creates a chain of 8,192 capacitors. Like the water buckets, an audio signal is passed from capacitor to capacitor within the BBD chips once every clock step. A slower clock produces a longer delay and a faster clock produces a shorter delay.
Delay time is set by adjusting the DELAY TIME SLIDER. Moving the slider up increases the delay time. Delay time can be voltage controlled by patching into the DELAY TIME CV INPUT JACK and adjusting the DELAY TIME CV TRIMMER. The DELAY TIME CV TRIMMER is an attenuverter. That means the incoming signal is off when the trimmer is set to the 12 o’clock position. Turning the attenuverter to the right passes the original signal through. Turning the attenuverter to the left passes an inverted version of the original signal through. Turning the DELAY TIME CV TRIMMER to the right will increase the amount of CV passed through to the delay time. Turning the DELAY TIME CV TRIMMER to the left will increase the amount of inverted CV passed through to the delay time. Locating the exact off position of an attenuverter can be difficult. The easiest wave to remove the CV signal from the signal path is to simply remove the patch cable patched into the DELAY TIME CV INPUT JACK.
The DELAY REPEATS SLIDER sets the amount of repeats created by the delay. Moving the DELAY REPEATSSLIDER all the way down will produce 1 repeat. Adjusting the slider up increases the number of repeats until the delay begins to self-oscillate. The Analog Delay Unit self-oscillates between approximately 55Hz to 500Hz depending on the position of the DELAY TIME SLIDER.
The DELAY MIX KNOB acts as a balance control between the dry incoming signal and the wet delayed signal. Turning the DELAY MIX KNOB to the left weighs the output toward the dry signal. Turning the DELAY MIX KNOB to the right weighs the output toward the wet signal. In theory, setting the DELAY MIX KNOB at 12 o’clock creates an even mix of the wet and dry signals. In reality, the tolerance of the potentiometer, waves shape, and dry signal level all influence the location of an even 50/50 mix.
Panel size: 6hp
Power Usage: +12v 44mA, -12v 19mA. Does not require +5v. Reversed power polarity protection.