Reverb
Reverb is what a delay effect becomes when you stop counting individual repeats and instead simulate thousands of them arriving so densely they blur into a continuous decay. This chapter covers the physical spring-tank mechanism behind classic spring reverb and the digital delay-network alternative that replaces springs with math.
Reverb and delay are close relatives: a delay gives you back a handful of discrete, countable repeats, while reverb simulates thousands of reflections arriving so closely together that they blur into a single, continuous decaying wash instead of individual echoes. Where the two circuit families genuinely diverge is how that dense wash of reflections gets generated — and the two dominant answers, a physical spring and a digital delay network, don’t share a single component between them.
Spring reverb: sound converted to mechanical motion and back
A spring reverb tank does something no other circuit in this book does: it converts the electrical signal into physical motion, sends that motion down a real spring, and converts it back. A transducer at one end of the spring vibrates the spring itself in response to the incoming signal; a second transducer at the other end picks up whatever vibration arrives and turns it back into an electrical signal. Because a spring is a physical object with its own resonances, dispersion (different frequencies genuinely travel down the spring at different speeds), and multiple internal reflection paths bouncing between its ends, the recovered signal comes back smeared in time and colored in a specific, slightly metallic way that’s the entire reason spring reverb has its own distinct, recognizable identity rather than sounding like a generic “echo.”
Digital reverb: the same dense-reflection idea, built from delay lines instead of springs
A digital or algorithmic reverb has no physical spring anywhere in it — it recreates the same “thousands of overlapping reflections” idea using a network of short digital delay lines with feedback paths between them (commonly called a feedback delay network, or FDN), tuned so their combined output decays smoothly and densely rather than as a handful of countable repeats. This is a direct extension of the delay circuitry covered in Delay: the same circular-buffer mechanism that produces a single countable echo produces a convincing reverb wash when enough delay lines of different, carefully chosen lengths feed back into each other simultaneously. DaisySP, the DSP building-block library covered in the Electrosmith Daisy Guide, ships a ready-made reverb building block built exactly this way, so a Daisy-based pedal gets access to this circuit without hand-deriving the delay-network math from scratch.
| Spring reverb | Digital (algorithmic) reverb | |
|---|---|---|
| Mechanism | Physical spring, driven and recovered by transducers | Network of digital delay lines with feedback (FDN) |
| Character | Distinct, slightly metallic, dispersive “boing” quality | Configurable — can range from spring-like to hall- or room-like, depending on how the delay network is tuned |
| Physical size/footprint | Requires a physical spring tank, historically a real space constraint in an enclosure | No moving parts — footprint is whatever the code and a Daisy Seed require |
| Handling consideration | Mechanically resonant — physical shock produces an audible “crash” through the circuit itself | None — a purely electrical signal chain, unaffected by physically jostling the pedal |
Common mistake: treating a spring tank like an ordinary circuit board when handling it
A spring reverb tank isn’t just electrically sensitive the way any circuit is — it’s mechanically sensitive in a way nothing else in this book is, because the spring is a real, physically resonant object that converts a knock or a drop directly into an audible signal through the same transducers doing the reverb effect on purpose. This is a genuine, load-bearing part of spring reverb’s identity (the “crash” from kicking a tube amp with a built-in spring tank is a real, well-known effect players intentionally use), but it also means a spring tank has to be mounted and handled with actual physical care during a build or when transporting a finished pedal — something no other circuit in the Effects book requires thinking about at all.