This project can be used as a blueprint for making simple preamplifiers for contact mic's (or other stuff). It's put together to allow you to experiment and find unexpected joys.
If you want something that definitely works well, there are simple recipes to follow. If you want to stray off of the map, you can substitute components and see where they lead you. The experimental approach won't always work but I've had surprising, non-linear, results that have been fun to work with.
The Contingent Piezo Preamp grew out of a research project. Whilst investigating common contact mic preamp circuits found online, I noticed a common pattern and wondered if I could design a kind of meta-schematic. I also mucked around when testing circuits and was surprised that many still worked even if I veered from the schematic values.
This is the result of those investigations. I can't guarantee the best preamp but half the fun is in trying new things ✌️??
Pricing is the minimum possible (plus p&p) or pay more if you can/want. You can download a pdf for free either bundled with this print edition or over on my portfolio website - mroystonward.com
Whilst building a range of preamps, sourced from various websites, for use with piezo contact microphones, I also randomly prototyped different component values, just to see what would happen. The original designs seemed quite resilient to such changes, still generally working well. I also noticed a shared design pattern and imagined a possible meta-circuit that could also accommodate my variations and open up a space for randomness and contingency. This birthed a project called the CNTNGNT PRMP, a paper circuit designed for radically open DIY circuit building.
I built a random selection of twenty CNTNGT PRMPS, of which only seven worked well enough to use. Each of these seven were tested by simply using a contact mic, through a preamplifier, with a belt-clip mini-amp. I would move the contact mic to find a sweet spot where I could leave it alone and it would exhibit some liveliness, some self-playing moments of instability and movement. I let these play out until the feedback loop had either fallen apart or descended into a single, unmoving tone. I would then continue to search for another sweet spot, rinse, repeat.
Differences in sound and self-playing are generally a result of different gain structures within these preamps, themselves a result of random component selection and inconsistent component manufacturing tolerances. Three circuits, in particular, displayed surprising and non-linear behaviour, responding to my explorations in unusual ways, resisting attempts to find sweet spots, and breaking into unexpected bursts of vibrant sound.
Whilst documenting, I simply put each new recording on a new track within my DAW. When reviewing, I forgot to mute the tracks I didn’t want to hear and was faced with a cacophony of multiple circuits all playing at once. What struck me was that the total excess and exuberance of seven feedback circuits all squealing simultaneously seemed more suggestive of the liveliness inherent in these systems than any one recording alone. I am reminded of Herzog’s jungle, humbled before the overwhelming chaos.