Tape, bucket brigade and digital delay

Tape and BBD can both give you a dark echo, but changing the delay time in Drift Delay shows a difference between them. BBD gets darker as you turn the time up. Tape applies the same high-frequency loss per pass at any delay time.

The models also differ in their bass response, level handling and noise.

Digital

The Digital model leaves the delay line uncoloured. With drive, filters and the other colour controls off, the repeats keep their tone as they fade.

Use it for a crisp slapback or a rhythmic part where you want to hear the attack of each repeat. It's also a useful starting point when you're setting up the filters: you can hear what they're doing without the model adding its own colour.

Tape: loss per pass, and a bump at 80 Hz

The Tape model rolls off the high end on each repeat and adds a low-frequency bump around 80 Hz, modelling the head bump of a tape machine.

The high-end loss accumulates just as it does with the in-loop filters. Repeat five has been through it five times. At high feedback settings, the later repeats can get quite muddy.

The bass bump needs care inside a feedback loop. If it pushes the total loop gain above one at that frequency, a low rumble can build up instead of decaying.

BBD: darker at longer delay times

A bucket-brigade device is a chain of capacitors that pass charge from one to the next. A clock controls how quickly they do it: a slower clock gives a longer delay. The filtering follows the clock rate, so the available bandwidth falls as the delay gets longer.

In Drift Delay's BBD model, you can hear this by moving from a short slapback to a long echo. Keep the other controls fixed and the longer setting will sound darker. The Tape model's filtering stays the same when you change delay time.

Keeping the compander from shortening the tail

Tape and BBD have an optional compander: a compressor before the delay line, paired with an expander after it. This controls the level going through the line and restores the dynamics on playback. Digital bypasses it.

Using separate level detectors for compression and expansion caused a problem on sparse material. During the gaps between woodblock or rimshot hits, both detector envelopes decayed. The expander no longer undid the compressor's gain change, and the loop lost extra level on every pass. It was harder to hear on dense material, where the detectors tracked more closely.

Drift Delay records the compressor gain alongside each audio sample in a parallel delay line. On playback, the expander reads that gain from the same head positions as the audio and applies its reciprocal. That keeps the compander from shortening the feedback decay on sparse input.

Quiet tails can still receive a lift of up to 12 dB in total across their repeats. This brings up the quieter part of the sound without adding an unbounded gain boost on every pass.

Noise

The Floor control adds hiss inside the loop. Low is quieter; Vint is louder and darker. With Compand enabled, expansion gates the noise with the signal, so it fades with the echoes.

Try it on a sparse part where there's room to hear the tail. Leave Floor off if you don't want the hiss.

Starting points

• Digital for clear repeats that keep their attack.
• Tape for repeats that gradually lose their top end, or a darker wash at high feedback.
• BBD for short, bright slapbacks or longer, darker echoes.

The models share the rest of Drift Delay's controls. Switch between them with the other settings fixed to hear what each one adds.