Red-Eye Preamp - Transducers, Piezo Pickups & Mics

Question…

You have mentioned that Red-Eye preamps work well with piezoelectric pickups, but how do you find them with transducer pickups like K&k and also something like the anthem where there is a transducer mic?  What’s the difference between a transducer and a piezo pickup?

Response…

Engineering terms...

A “transducer” is any device that can change one form of energy to another.  For example...

  -- A microphone is a transducer that changes sound energy (variations in the pressure of air) into electrical energy (variations in voltage and current)

  -- A loud speaker is a transducer that changes electrical energy into sound energy.

  -- A turbine-generator in a hydroelectric dam is a transducer that changes the energy in water pressure and velocity into electrical energy.

  -- The engine in a car can be thought of as being a transducer that changes the chemical energy in gasoline or diesel into mechanical energy of motion.

Piezoelectric transducer...

Piezoelectric materials change mechanical pressure and bending into electrical energy and vice-versa.  There are many materials that do that.  Certain inorganic crystals such as quartz or alumina are piezo materials.  So are several organic plastics.  There is a wide variety of piezo materials for pickup designers to choose from.  So, pickups of many shapes and sizes and made of a variety of piezoelectric materials are on the market.

K&K pickups...

Like many other pickups, the K&K uses a piezoelectric material as a transducer to change mechanical vibration energy into electrical energy.  These pickups seem to be exceptionally well engineered, and combined with a preamp that properly matches the electrical impedance of the pickup, they can perform very well.

Different subject:  Microphones in instruments...

For performing musicians, microphones built into instruments are a bad idea.  A performing musician is just asking for feedback problems if he or she tries to use an instrument with a built-in mic on stage, particularly if the sound must be amplified a lot. 

Contact pickups like the K&K mini are much less sensitive to feedback and cause fewer problems in performance situations.

Active pickups...

Active pickups consist of a pickup and a preamp built into an instrument.  I measured several of the preamps built into guitars and discovered that none of the ones I measured had a preamp that properly matched the impedance of the pickup.  Perhaps the pickup in that situation may be excellent, but the energy from the pickup cannot couple into the preamp properly if the impedance doesn’t match.

And, of course, active pickups have a battery to power the preamp.  I’ve been to way too many concerts where the battery died during the performance.  Nasty!  I don’t think batteries belong in a fine instrument.

Daren Appelt, Engineer, Fire-Eye Development, Inc.