TankDriver™ Development

The first question is: With today's unbelievable digital technology, why would anyone want a spring reverb? The answer: there is something funky, unique and unpredictable about a spring reverb that is simply impossible to reproduce using a digital algorithm. It is a distinctive effect that still today is preferred over digital counterparts, particularly on guitars.

So we started thinking about it. One idea was to try to use miniature springs and have them fit inside a 500 series module. But the more we played around with the mechanics; we soon came to realize that for a spring to work well, it needs to be long enough to generate a natural decay. We then thought about making a driver and then a separate 19" rack for the reverb tank. And although we may eventually do this, we realized that we already had a bunch of reverb tanks… they were all sitting inside the amps in our R&D test area. It occurred to us that most people have a reverb tank, they just aren't using it. So the Tank Driver was born.

We basically used the design layout we developed for the EXTC as a base, redid the circuit to optimize it for reverb tanks, added some EQ controls and then quickly found out that getting great sound from a reverb tank is not all that easy. Spring reverbs are not much more advanced than two paper cups and a piece of string.

How a Spring Reverb Works

A spring reverb works along the same lines as an electric guitar pickup. Only in this case, there are two transducers with one at each end. The electrical signal is sent to a coil and inside the coil is a steel bar. When current is applied to the coil, it causes the bar to vibrate like a guitar string. This is connected to a spring. The vibrations travel along the length of the spring over time. When the vibrations arrive at the other end, these cause a second steel bar to move. (like a guitar string that vibrates back and forth) As the steel bar moves in and around the coil, sound is generated – just like a guitar pickup. Presto, you now have reverb!

During our tests, we found that adding some tone control could greatly help in creating nice sounds. Thus the reason for the shimmer and boom controls. We then found that with certain types of reverbs, the drive required to agitate the spring needed to increase. Thus the reason we added a drive switch. This basically boosts the intensity going to the spring.

The real fun sets in when you compare the tone of one spring reverb with another. Some are brighter, some are shorter, some have more initial attack, others longer decay times. And best of all, you probably have a bunch of these already in your studio and all you need to do to make the work is find a couple of 1./4" to RCA cables and you are well on your way to adding spring reverb flowers to your sunshiny day!