Spring Reverb Module

After a nice long summer holiday with plenty of time for contemplation and relaxing, I felt it was time to return to the workshop and strike while the soldering-iron was hot so I finally finished my spring reverb module which had caused me some headaches during the spring time (no pun here). During trouble shooting, I've learned a lot about operational amplifiers which will be useful in future builds.

Here's the finalized contraption in action!

It's basically a Spring Reverb Tank (the ones you find in old guitar amps) for which I've made an amplifier-circuit. The 'IN' knob controls the gain for the signal sent into the spring, the 'DRY' knob lets through some of the clean signal to the internal mixer circuit and the 'WET' knob sets the gain for the signal from the spring tank to the mixer. This lets you just plug one jack-cable into the module and adjust how much of the clean signal you want to blend with the reverbed sound - saves a lot of cable mess. The input gain acts as a kind of "decay time" as it somewhat determines how long the spring will vibrate for because of the amplitude sent to the spring.

I also found out that you can get nice feeding oscillations if you turn off the input sound! (happens in the end of the video)

I feel this is kind of a 'must have, must build' module for anyone serious about having a handmade modular setup, so I was very determined to get this done and now I am so relieved about finally having this mo-fo boxed and good to go so I can focus on the larger projects I am about to unveil for you good folks out there!

Here's my scheme for the amplifier-circuit:


I chose to use seperate ICs to avoid bleeding of the signals, which I encountered on the test-board. I see that I didn't bias the mixing stage, but it sounds good without.