Design Notes

Input Stage

The outputs on audio interfaces, converters, and consoles are line outputs. They send a voltage (around 1 or 2 volts) that represents the waveform, and the device receiving it reads that voltage.

It's helpful to think of the input side of a spring reverb tank as being similar to a speaker. A coil of wire sits in a magnetic field, but instead of moving a cone, it's attached to one end of the springs.¹

Speakers and headphones need power to be driven, which is why they have amplifiers. A line output sends voltage but does not have enough current to make anything move.

stereospring includes a drive stage that turns the line signal into enough current to drive the springs.²

Output Stage

At the other end of the tank is a second coil that works in reverse. The springs move it, and that motion becomes voltage. Dynamic microphones work in a similar way, when air moves a thin diaphragm attached to a coil, sitting in a magnetic field.

Like a microphone, what comes out is very small and needs a lot of gain to be useful.

External Preamps

Most spring reverbs put a preamp inside the box for makeup gain. But with stereospring, the tank output goes straight to an XLR at mic level and requires you to use your own preamps.

This decision came down mainly to cost. High quality preamps are expensive. Rather than paying for more preamps, you can use what you already have.